Import cc 1.0.79upstream/1.0.79upstream

20 files changed, 7076 insertions, 0 deletions

diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
new file mode 100644
index 0000000..6649dfa
--- /dev/null
+++ b/.cargo_vcs_info.json
@@ -0,0 +1,6 @@
+{
+  "git": {
+    "sha1": "e5bbdfa1fa468c028cb38fee6c35a3cf2e5a2736"
+  },
+  "path_in_vcs": ""
+}
\ No newline at end of file
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..3b874ca
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+target
+Cargo.lock
+.idea
+*.iml
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..bbdd986
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,39 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+name = "cc"
+version = "1.0.79"
+authors = ["Alex Crichton <alex@alexcrichton.com>"]
+exclude = ["/.github"]
+description = """
+A build-time dependency for Cargo build scripts to assist in invoking the native
+C compiler to compile native C code into a static archive to be linked into Rust
+code.
+"""
+homepage = "https://github.com/rust-lang/cc-rs"
+documentation = "https://docs.rs/cc"
+readme = "README.md"
+keywords = ["build-dependencies"]
+categories = ["development-tools::build-utils"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/rust-lang/cc-rs"
+
+[dependencies.jobserver]
+version = "0.1.16"
+optional = true
+
+[dev-dependencies.tempfile]
+version = "3"
+
+[features]
+parallel = ["jobserver"]
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..3128f03
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,27 @@
+[package]
+name = "cc"
+version = "1.0.79"
+authors = ["Alex Crichton <alex@alexcrichton.com>"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/rust-lang/cc-rs"
+homepage = "https://github.com/rust-lang/cc-rs"
+documentation = "https://docs.rs/cc"
+description = """
+A build-time dependency for Cargo build scripts to assist in invoking the native
+C compiler to compile native C code into a static archive to be linked into Rust
+code.
+"""
+keywords = ["build-dependencies"]
+readme = "README.md"
+categories = ["development-tools::build-utils"]
+exclude = ["/.github"]
+edition = "2018"
+
+[dependencies]
+jobserver = { version = "0.1.16", optional = true }
+
+[features]
+parallel = ["jobserver"]
+
+[dev-dependencies]
+tempfile = "3"
diff --git a/LICENSE-APACHE b/LICENSE-APACHE
new file mode 100644
index 0000000..16fe87b
--- /dev/null
+++ b/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
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+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
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+   Contributor provides its Contributions) on an "AS IS" BASIS,
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+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
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+Unless required by applicable law or agreed to in writing, software
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diff --git a/LICENSE-MIT b/LICENSE-MIT
new file mode 100644
index 0000000..39e0ed6
--- /dev/null
+++ b/LICENSE-MIT
@@ -0,0 +1,25 @@
+Copyright (c) 2014 Alex Crichton
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..863540d
--- /dev/null
+++ b/README.md
@@ -0,0 +1,223 @@
+# cc-rs
+
+A library to compile C/C++/assembly into a Rust library/application.
+
+[Documentation](https://docs.rs/cc)
+
+A simple library meant to be used as a build dependency with Cargo packages in
+order to build a set of C/C++ files into a static archive. This crate calls out
+to the most relevant compiler for a platform, for example using `cl` on MSVC.
+
+## Using cc-rs
+
+First, you'll want to both add a build script for your crate (`build.rs`) and
+also add this crate to your `Cargo.toml` via:
+
+```toml
+[build-dependencies]
+cc = "1.0"
+```
+
+Next up, you'll want to write a build script like so:
+
+```rust,no_run
+// build.rs
+
+fn main() {
+    cc::Build::new()
+        .file("foo.c")
+        .file("bar.c")
+        .compile("foo");
+}
+```
+
+And that's it! Running `cargo build` should take care of the rest and your Rust
+application will now have the C files `foo.c` and `bar.c` compiled into a file
+named `libfoo.a`. If the C files contain
+
+```c
+void foo_function(void) { ... }
+```
+
+and
+
+```c
+int32_t bar_function(int32_t x) { ... }
+```
+
+you can call them from Rust by declaring them in
+your Rust code like so:
+
+```rust,no_run
+extern {
+    fn foo_function();
+    fn bar_function(x: i32) -> i32;
+}
+
+pub fn call() {
+    unsafe {
+        foo_function();
+        bar_function(42);
+    }
+}
+
+fn main() {
+    // ...
+}
+```
+
+See [the Rustonomicon](https://doc.rust-lang.org/nomicon/ffi.html) for more details.
+
+## External configuration via environment variables
+
+To control the programs and flags used for building, the builder can set a
+number of different environment variables.
+
+* `CFLAGS` - a series of space separated flags passed to compilers. Note that
+             individual flags cannot currently contain spaces, so doing
+             something like: `-L=foo\ bar` is not possible.
+* `CC` - the actual C compiler used. Note that this is used as an exact
+         executable name, so (for example) no extra flags can be passed inside
+         this variable, and the builder must ensure that there aren't any
+         trailing spaces. This compiler must understand the `-c` flag. For
+         certain `TARGET`s, it also is assumed to know about other flags (most
+         common is `-fPIC`).
+* `AR` - the `ar` (archiver) executable to use to build the static library.
+* `CRATE_CC_NO_DEFAULTS` - the default compiler flags may cause conflicts in some cross compiling scenarios. Setting this variable will disable the generation of default compiler flags.
+* `CXX...` - see [C++ Support](#c-support).
+
+Each of these variables can also be supplied with certain prefixes and suffixes,
+in the following prioritized order:
+
+1. `<var>_<target>` - for example, `CC_x86_64-unknown-linux-gnu`
+2. `<var>_<target_with_underscores>` - for example, `CC_x86_64_unknown_linux_gnu`
+3. `<build-kind>_<var>` - for example, `HOST_CC` or `TARGET_CFLAGS`
+4. `<var>` - a plain `CC`, `AR` as above.
+
+If none of these variables exist, cc-rs uses built-in defaults
+
+In addition to the above optional environment variables, `cc-rs` has some
+functions with hard requirements on some variables supplied by [cargo's
+build-script driver][cargo] that it has the `TARGET`, `OUT_DIR`, `OPT_LEVEL`,
+and `HOST` variables.
+
+[cargo]: https://doc.rust-lang.org/cargo/reference/build-scripts.html#inputs-to-the-build-script
+
+## Optional features
+
+### Parallel
+
+Currently cc-rs supports parallel compilation (think `make -jN`) but this
+feature is turned off by default. To enable cc-rs to compile C/C++ in parallel,
+you can change your dependency to:
+
+```toml
+[build-dependencies]
+cc = { version = "1.0", features = ["parallel"] }
+```
+
+By default cc-rs will limit parallelism to `$NUM_JOBS`, or if not present it
+will limit it to the number of cpus on the machine. If you are using cargo,
+use `-jN` option of `build`, `test` and `run` commands as `$NUM_JOBS`
+is supplied by cargo.
+
+## Compile-time Requirements
+
+To work properly this crate needs access to a C compiler when the build script
+is being run. This crate does not ship a C compiler with it. The compiler
+required varies per platform, but there are three broad categories:
+
+* Unix platforms require `cc` to be the C compiler. This can be found by
+  installing cc/clang on Linux distributions and Xcode on macOS, for example.
+* Windows platforms targeting MSVC (e.g. your target triple ends in `-msvc`)
+  require `cl.exe` to be available and in `PATH`. This is typically found in
+  standard Visual Studio installations and the `PATH` can be set up by running
+  the appropriate developer tools shell.
+* Windows platforms targeting MinGW (e.g. your target triple ends in `-gnu`)
+  require `cc` to be available in `PATH`. We recommend the
+  [MinGW-w64](https://www.mingw-w64.org/) distribution, which is using the
+  [Win-builds](http://win-builds.org/) installation system.
+  You may also acquire it via
+  [MSYS2](https://www.msys2.org/), as explained [here][msys2-help].  Make sure
+  to install the appropriate architecture corresponding to your installation of
+  rustc. GCC from older [MinGW](http://www.mingw.org/) project is compatible
+  only with 32-bit rust compiler.
+
+[msys2-help]: https://github.com/rust-lang/rust#building-on-windows
+
+## C++ support
+
+`cc-rs` supports C++ libraries compilation by using the `cpp` method on
+`Build`:
+
+```rust,no_run
+fn main() {
+    cc::Build::new()
+        .cpp(true) // Switch to C++ library compilation.
+        .file("foo.cpp")
+        .compile("libfoo.a");
+}
+```
+
+For C++ libraries, the `CXX` and `CXXFLAGS` environment variables are used instead of `CC` and `CFLAGS`.
+
+The C++ standard library may be linked to the crate target. By default it's `libc++` for macOS, FreeBSD, and OpenBSD, `libc++_shared` for Android, nothing for MSVC, and `libstdc++` for anything else. It can be changed in one of two ways:
+
+1. by using the `cpp_link_stdlib` method on `Build`:
+    ```rust,no-run
+    fn main() {
+        cc::Build::new()
+            .cpp(true)
+            .file("foo.cpp")
+            .cpp_link_stdlib("stdc++") // use libstdc++
+            .compile("libfoo.a");
+    }
+    ```
+2. by setting the `CXXSTDLIB` environment variable.
+
+In particular, for Android you may want to [use `c++_static` if you have at most one shared library](https://developer.android.com/ndk/guides/cpp-support).
+
+Remember that C++ does name mangling so `extern "C"` might be required to enable Rust linker to find your functions.
+
+## CUDA C++ support
+
+`cc-rs` also supports compiling CUDA C++ libraries by using the `cuda` method
+on `Build` (currently for GNU/Clang toolchains only):
+
+```rust,no_run
+fn main() {
+    cc::Build::new()
+        // Switch to CUDA C++ library compilation using NVCC.
+        .cuda(true)
+        .cudart("static")
+        // Generate code for Maxwell (GTX 970, 980, 980 Ti, Titan X).
+        .flag("-gencode").flag("arch=compute_52,code=sm_52")
+        // Generate code for Maxwell (Jetson TX1).
+        .flag("-gencode").flag("arch=compute_53,code=sm_53")
+        // Generate code for Pascal (GTX 1070, 1080, 1080 Ti, Titan Xp).
+        .flag("-gencode").flag("arch=compute_61,code=sm_61")
+        // Generate code for Pascal (Tesla P100).
+        .flag("-gencode").flag("arch=compute_60,code=sm_60")
+        // Generate code for Pascal (Jetson TX2).
+        .flag("-gencode").flag("arch=compute_62,code=sm_62")
+        .file("bar.cu")
+        .compile("libbar.a");
+}
+```
+
+## License
+
+This project is licensed under either of
+
+ * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
+   https://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or
+   https://opensource.org/licenses/MIT)
+
+at your option.
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in cc-rs by you, as defined in the Apache-2.0 license, shall be
+dual licensed as above, without any additional terms or conditions.
diff --git a/src/bin/gcc-shim.rs b/src/bin/gcc-shim.rs
new file mode 100644
index 0000000..e5b5372
--- /dev/null
+++ b/src/bin/gcc-shim.rs
@@ -0,0 +1,70 @@
+#![cfg_attr(test, allow(dead_code))]
+
+use std::env;
+use std::fs::File;
+use std::io::{self, prelude::*};
+use std::path::PathBuf;
+
+fn main() {
+    let mut args = env::args();
+    let program = args.next().expect("Unexpected empty args");
+
+    let out_dir = PathBuf::from(
+        env::var_os("GCCTEST_OUT_DIR")
+            .unwrap_or_else(|| panic!("{}: GCCTEST_OUT_DIR not found", program)),
+    );
+
+    // Find the first nonexistent candidate file to which the program's args can be written.
+    let candidate = (0..).find_map(|i| {
+        let candidate = out_dir.join(format!("out{}", i));
+
+        if candidate.exists() {
+            // If the file exists, commands have already run. Try again.
+            None
+        } else {
+            Some(candidate)
+        }
+    }).unwrap_or_else(|| panic!("Cannot find the first nonexistent candidate file to which the program's args can be written under out_dir '{}'", out_dir.display()));
+
+    // Create a file and record the args passed to the command.
+    let f = File::create(&candidate).unwrap_or_else(|e| {
+        panic!(
+            "{}: can't create candidate: {}, error: {}",
+            program,
+            candidate.display(),
+            e
+        )
+    });
+    let mut f = io::BufWriter::new(f);
+
+    (|| {
+        for arg in args {
+            writeln!(f, "{}", arg)?;
+        }
+
+        f.flush()?;
+
+        let mut f = f.into_inner()?;
+        f.flush()?;
+        f.sync_all()
+    })()
+    .unwrap_or_else(|e| {
+        panic!(
+            "{}: can't write to candidate: {}, error: {}",
+            program,
+            candidate.display(),
+            e
+        )
+    });
+
+    // Create a file used by some tests.
+    let path = &out_dir.join("libfoo.a");
+    File::create(path).unwrap_or_else(|e| {
+        panic!(
+            "{}: can't create libfoo.a: {}, error: {}",
+            program,
+            path.display(),
+            e
+        )
+    });
+}
diff --git a/src/com.rs b/src/com.rs
new file mode 100644
index 0000000..843247e
--- /dev/null
+++ b/src/com.rs
@@ -0,0 +1,155 @@
+// Copyright © 2017 winapi-rs developers
+// Licensed under the Apache License, Version 2.0
+// <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
+// All files in the project carrying such notice may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(unused)]
+
+use crate::winapi::CoInitializeEx;
+use crate::winapi::IUnknown;
+use crate::winapi::Interface;
+use crate::winapi::BSTR;
+use crate::winapi::COINIT_MULTITHREADED;
+use crate::winapi::{SysFreeString, SysStringLen};
+use crate::winapi::{HRESULT, S_FALSE, S_OK};
+use std::ffi::{OsStr, OsString};
+use std::mem::forget;
+use std::ops::Deref;
+use std::os::windows::ffi::{OsStrExt, OsStringExt};
+use std::ptr::null_mut;
+use std::slice::from_raw_parts;
+
+pub fn initialize() -> Result<(), HRESULT> {
+    let err = unsafe { CoInitializeEx(null_mut(), COINIT_MULTITHREADED) };
+    if err != S_OK && err != S_FALSE {
+        // S_FALSE just means COM is already initialized
+        return Err(err);
+    }
+    Ok(())
+}
+
+pub struct ComPtr<T>(*mut T)
+where
+    T: Interface;
+impl<T> ComPtr<T>
+where
+    T: Interface,
+{
+    /// Creates a `ComPtr` to wrap a raw pointer.
+    /// It takes ownership over the pointer which means it does __not__ call `AddRef`.
+    /// `T` __must__ be a COM interface that inherits from `IUnknown`.
+    pub unsafe fn from_raw(ptr: *mut T) -> ComPtr<T> {
+        assert!(!ptr.is_null());
+        ComPtr(ptr)
+    }
+    /// Casts up the inheritance chain
+    pub fn up<U>(self) -> ComPtr<U>
+    where
+        T: Deref<Target = U>,
+        U: Interface,
+    {
+        ComPtr(self.into_raw() as *mut U)
+    }
+    /// Extracts the raw pointer.
+    /// You are now responsible for releasing it yourself.
+    pub fn into_raw(self) -> *mut T {
+        let p = self.0;
+        forget(self);
+        p
+    }
+    /// For internal use only.
+    fn as_unknown(&self) -> &IUnknown {
+        unsafe { &*(self.0 as *mut IUnknown) }
+    }
+    /// Performs QueryInterface fun.
+    pub fn cast<U>(&self) -> Result<ComPtr<U>, i32>
+    where
+        U: Interface,
+    {
+        let mut obj = null_mut();
+        let err = unsafe { self.as_unknown().QueryInterface(&U::uuidof(), &mut obj) };
+        if err < 0 {
+            return Err(err);
+        }
+        Ok(unsafe { ComPtr::from_raw(obj as *mut U) })
+    }
+}
+impl<T> Deref for ComPtr<T>
+where
+    T: Interface,
+{
+    type Target = T;
+    fn deref(&self) -> &T {
+        unsafe { &*self.0 }
+    }
+}
+impl<T> Clone for ComPtr<T>
+where
+    T: Interface,
+{
+    fn clone(&self) -> Self {
+        unsafe {
+            self.as_unknown().AddRef();
+            ComPtr::from_raw(self.0)
+        }
+    }
+}
+impl<T> Drop for ComPtr<T>
+where
+    T: Interface,
+{
+    fn drop(&mut self) {
+        unsafe {
+            self.as_unknown().Release();
+        }
+    }
+}
+pub struct BStr(BSTR);
+impl BStr {
+    pub unsafe fn from_raw(s: BSTR) -> BStr {
+        BStr(s)
+    }
+    pub fn to_osstring(&self) -> OsString {
+        let len = unsafe { SysStringLen(self.0) };
+        let slice = unsafe { from_raw_parts(self.0, len as usize) };
+        OsStringExt::from_wide(slice)
+    }
+}
+impl Drop for BStr {
+    fn drop(&mut self) {
+        unsafe { SysFreeString(self.0) };
+    }
+}
+
+pub trait ToWide {
+    fn to_wide(&self) -> Vec<u16>;
+    fn to_wide_null(&self) -> Vec<u16>;
+}
+impl<T> ToWide for T
+where
+    T: AsRef<OsStr>,
+{
+    fn to_wide(&self) -> Vec<u16> {
+        self.as_ref().encode_wide().collect()
+    }
+    fn to_wide_null(&self) -> Vec<u16> {
+        self.as_ref().encode_wide().chain(Some(0)).collect()
+    }
+}
+pub trait FromWide
+where
+    Self: Sized,
+{
+    fn from_wide(wide: &[u16]) -> Self;
+    fn from_wide_null(wide: &[u16]) -> Self {
+        let len = wide.iter().take_while(|&&c| c != 0).count();
+        Self::from_wide(&wide[..len])
+    }
+}
+impl FromWide for OsString {
+    fn from_wide(wide: &[u16]) -> OsString {
+        OsStringExt::from_wide(wide)
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..abc5d7a
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,3712 @@
+//! A library for build scripts to compile custom C code
+//!
+//! This library is intended to be used as a `build-dependencies` entry in
+//! `Cargo.toml`:
+//!
+//! ```toml
+//! [build-dependencies]
+//! cc = "1.0"
+//! ```
+//!
+//! The purpose of this crate is to provide the utility functions necessary to
+//! compile C code into a static archive which is then linked into a Rust crate.
+//! Configuration is available through the `Build` struct.
+//!
+//! This crate will automatically detect situations such as cross compilation or
+//! other environment variables set by Cargo and will build code appropriately.
+//!
+//! The crate is not limited to C code, it can accept any source code that can
+//! be passed to a C or C++ compiler. As such, assembly files with extensions
+//! `.s` (gcc/clang) and `.asm` (MSVC) can also be compiled.
+//!
+//! [`Build`]: struct.Build.html
+//!
+//! # Parallelism
+//!
+//! To parallelize computation, enable the `parallel` feature for the crate.
+//!
+//! ```toml
+//! [build-dependencies]
+//! cc = { version = "1.0", features = ["parallel"] }
+//! ```
+//! To specify the max number of concurrent compilation jobs, set the `NUM_JOBS`
+//! environment variable to the desired amount.
+//!
+//! Cargo will also set this environment variable when executed with the `-jN` flag.
+//!
+//! If `NUM_JOBS` is not set, the `RAYON_NUM_THREADS` environment variable can
+//! also specify the build parallelism.
+//!
+//! # Examples
+//!
+//! Use the `Build` struct to compile `src/foo.c`:
+//!
+//! ```no_run
+//! fn main() {
+//!     cc::Build::new()
+//!         .file("src/foo.c")
+//!         .define("FOO", Some("bar"))
+//!         .include("src")
+//!         .compile("foo");
+//! }
+//! ```
+
+#![doc(html_root_url = "https://docs.rs/cc/1.0")]
+#![cfg_attr(test, deny(warnings))]
+#![allow(deprecated)]
+#![deny(missing_docs)]
+
+use std::collections::{hash_map, HashMap};
+use std::env;
+use std::ffi::{OsStr, OsString};
+use std::fmt::{self, Display, Formatter};
+use std::fs;
+use std::hash::Hasher;
+use std::io::{self, BufRead, BufReader, Read, Write};
+use std::path::{Component, Path, PathBuf};
+use std::process::{Child, Command, Stdio};
+use std::sync::{Arc, Mutex};
+use std::thread::{self, JoinHandle};
+
+// These modules are all glue to support reading the MSVC version from
+// the registry and from COM interfaces
+#[cfg(windows)]
+mod registry;
+#[cfg(windows)]
+#[macro_use]
+mod winapi;
+#[cfg(windows)]
+mod com;
+#[cfg(windows)]
+mod setup_config;
+#[cfg(windows)]
+mod vs_instances;
+
+pub mod windows_registry;
+
+/// A builder for compilation of a native library.
+///
+/// A `Build` is the main type of the `cc` crate and is used to control all the
+/// various configuration options and such of a compile. You'll find more
+/// documentation on each method itself.
+#[derive(Clone, Debug)]
+pub struct Build {
+    include_directories: Vec<PathBuf>,
+    definitions: Vec<(String, Option<String>)>,
+    objects: Vec<PathBuf>,
+    flags: Vec<String>,
+    flags_supported: Vec<String>,
+    known_flag_support_status: Arc<Mutex<HashMap<String, bool>>>,
+    ar_flags: Vec<String>,
+    asm_flags: Vec<String>,
+    no_default_flags: bool,
+    files: Vec<PathBuf>,
+    cpp: bool,
+    cpp_link_stdlib: Option<Option<String>>,
+    cpp_set_stdlib: Option<String>,
+    cuda: bool,
+    cudart: Option<String>,
+    target: Option<String>,
+    host: Option<String>,
+    out_dir: Option<PathBuf>,
+    opt_level: Option<String>,
+    debug: Option<bool>,
+    force_frame_pointer: Option<bool>,
+    env: Vec<(OsString, OsString)>,
+    compiler: Option<PathBuf>,
+    archiver: Option<PathBuf>,
+    ranlib: Option<PathBuf>,
+    cargo_metadata: bool,
+    link_lib_modifiers: Vec<String>,
+    pic: Option<bool>,
+    use_plt: Option<bool>,
+    static_crt: Option<bool>,
+    shared_flag: Option<bool>,
+    static_flag: Option<bool>,
+    warnings_into_errors: bool,
+    warnings: Option<bool>,
+    extra_warnings: Option<bool>,
+    env_cache: Arc<Mutex<HashMap<String, Option<String>>>>,
+    apple_sdk_root_cache: Arc<Mutex<HashMap<String, OsString>>>,
+    emit_rerun_if_env_changed: bool,
+}
+
+/// Represents the types of errors that may occur while using cc-rs.
+#[derive(Clone, Debug)]
+enum ErrorKind {
+    /// Error occurred while performing I/O.
+    IOError,
+    /// Invalid architecture supplied.
+    ArchitectureInvalid,
+    /// Environment variable not found, with the var in question as extra info.
+    EnvVarNotFound,
+    /// Error occurred while using external tools (ie: invocation of compiler).
+    ToolExecError,
+    /// Error occurred due to missing external tools.
+    ToolNotFound,
+    /// One of the function arguments failed validation.
+    InvalidArgument,
+}
+
+/// Represents an internal error that occurred, with an explanation.
+#[derive(Clone, Debug)]
+pub struct Error {
+    /// Describes the kind of error that occurred.
+    kind: ErrorKind,
+    /// More explanation of error that occurred.
+    message: String,
+}
+
+impl Error {
+    fn new(kind: ErrorKind, message: &str) -> Error {
+        Error {
+            kind: kind,
+            message: message.to_owned(),
+        }
+    }
+}
+
+impl From<io::Error> for Error {
+    fn from(e: io::Error) -> Error {
+        Error::new(ErrorKind::IOError, &format!("{}", e))
+    }
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:?}: {}", self.kind, self.message)
+    }
+}
+
+impl std::error::Error for Error {}
+
+/// Configuration used to represent an invocation of a C compiler.
+///
+/// This can be used to figure out what compiler is in use, what the arguments
+/// to it are, and what the environment variables look like for the compiler.
+/// This can be used to further configure other build systems (e.g. forward
+/// along CC and/or CFLAGS) or the `to_command` method can be used to run the
+/// compiler itself.
+#[derive(Clone, Debug)]
+pub struct Tool {
+    path: PathBuf,
+    cc_wrapper_path: Option<PathBuf>,
+    cc_wrapper_args: Vec<OsString>,
+    args: Vec<OsString>,
+    env: Vec<(OsString, OsString)>,
+    family: ToolFamily,
+    cuda: bool,
+    removed_args: Vec<OsString>,
+}
+
+/// Represents the family of tools this tool belongs to.
+///
+/// Each family of tools differs in how and what arguments they accept.
+///
+/// Detection of a family is done on best-effort basis and may not accurately reflect the tool.
+#[derive(Copy, Clone, Debug, PartialEq)]
+enum ToolFamily {
+    /// Tool is GNU Compiler Collection-like.
+    Gnu,
+    /// Tool is Clang-like. It differs from the GCC in a sense that it accepts superset of flags
+    /// and its cross-compilation approach is different.
+    Clang,
+    /// Tool is the MSVC cl.exe.
+    Msvc { clang_cl: bool },
+}
+
+impl ToolFamily {
+    /// What the flag to request debug info for this family of tools look like
+    fn add_debug_flags(&self, cmd: &mut Tool, dwarf_version: Option<u32>) {
+        match *self {
+            ToolFamily::Msvc { .. } => {
+                cmd.push_cc_arg("-Z7".into());
+            }
+            ToolFamily::Gnu | ToolFamily::Clang => {
+                cmd.push_cc_arg(
+                    dwarf_version
+                        .map_or_else(|| "-g".into(), |v| format!("-gdwarf-{}", v))
+                        .into(),
+                );
+            }
+        }
+    }
+
+    /// What the flag to force frame pointers.
+    fn add_force_frame_pointer(&self, cmd: &mut Tool) {
+        match *self {
+            ToolFamily::Gnu | ToolFamily::Clang => {
+                cmd.push_cc_arg("-fno-omit-frame-pointer".into());
+            }
+            _ => (),
+        }
+    }
+
+    /// What the flags to enable all warnings
+    fn warnings_flags(&self) -> &'static str {
+        match *self {
+            ToolFamily::Msvc { .. } => "-W4",
+            ToolFamily::Gnu | ToolFamily::Clang => "-Wall",
+        }
+    }
+
+    /// What the flags to enable extra warnings
+    fn extra_warnings_flags(&self) -> Option<&'static str> {
+        match *self {
+            ToolFamily::Msvc { .. } => None,
+            ToolFamily::Gnu | ToolFamily::Clang => Some("-Wextra"),
+        }
+    }
+
+    /// What the flag to turn warning into errors
+    fn warnings_to_errors_flag(&self) -> &'static str {
+        match *self {
+            ToolFamily::Msvc { .. } => "-WX",
+            ToolFamily::Gnu | ToolFamily::Clang => "-Werror",
+        }
+    }
+
+    fn verbose_stderr(&self) -> bool {
+        *self == ToolFamily::Clang
+    }
+}
+
+/// Represents an object.
+///
+/// This is a source file -> object file pair.
+#[derive(Clone, Debug)]
+struct Object {
+    src: PathBuf,
+    dst: PathBuf,
+}
+
+impl Object {
+    /// Create a new source file -> object file pair.
+    fn new(src: PathBuf, dst: PathBuf) -> Object {
+        Object { src: src, dst: dst }
+    }
+}
+
+impl Build {
+    /// Construct a new instance of a blank set of configuration.
+    ///
+    /// This builder is finished with the [`compile`] function.
+    ///
+    /// [`compile`]: struct.Build.html#method.compile
+    pub fn new() -> Build {
+        Build {
+            include_directories: Vec::new(),
+            definitions: Vec::new(),
+            objects: Vec::new(),
+            flags: Vec::new(),
+            flags_supported: Vec::new(),
+            known_flag_support_status: Arc::new(Mutex::new(HashMap::new())),
+            ar_flags: Vec::new(),
+            asm_flags: Vec::new(),
+            no_default_flags: false,
+            files: Vec::new(),
+            shared_flag: None,
+            static_flag: None,
+            cpp: false,
+            cpp_link_stdlib: None,
+            cpp_set_stdlib: None,
+            cuda: false,
+            cudart: None,
+            target: None,
+            host: None,
+            out_dir: None,
+            opt_level: None,
+            debug: None,
+            force_frame_pointer: None,
+            env: Vec::new(),
+            compiler: None,
+            archiver: None,
+            ranlib: None,
+            cargo_metadata: true,
+            link_lib_modifiers: Vec::new(),
+            pic: None,
+            use_plt: None,
+            static_crt: None,
+            warnings: None,
+            extra_warnings: None,
+            warnings_into_errors: false,
+            env_cache: Arc::new(Mutex::new(HashMap::new())),
+            apple_sdk_root_cache: Arc::new(Mutex::new(HashMap::new())),
+            emit_rerun_if_env_changed: true,
+        }
+    }
+
+    /// Add a directory to the `-I` or include path for headers
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use std::path::Path;
+    ///
+    /// let library_path = Path::new("/path/to/library");
+    ///
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .include(library_path)
+    ///     .include("src")
+    ///     .compile("foo");
+    /// ```
+    pub fn include<P: AsRef<Path>>(&mut self, dir: P) -> &mut Build {
+        self.include_directories.push(dir.as_ref().to_path_buf());
+        self
+    }
+
+    /// Add multiple directories to the `-I` include path.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// # use std::path::Path;
+    /// # let condition = true;
+    /// #
+    /// let mut extra_dir = None;
+    /// if condition {
+    ///     extra_dir = Some(Path::new("/path/to"));
+    /// }
+    ///
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .includes(extra_dir)
+    ///     .compile("foo");
+    /// ```
+    pub fn includes<P>(&mut self, dirs: P) -> &mut Build
+    where
+        P: IntoIterator,
+        P::Item: AsRef<Path>,
+    {
+        for dir in dirs {
+            self.include(dir);
+        }
+        self
+    }
+
+    /// Specify a `-D` variable with an optional value.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .define("FOO", "BAR")
+    ///     .define("BAZ", None)
+    ///     .compile("foo");
+    /// ```
+    pub fn define<'a, V: Into<Option<&'a str>>>(&mut self, var: &str, val: V) -> &mut Build {
+        self.definitions
+            .push((var.to_string(), val.into().map(|s| s.to_string())));
+        self
+    }
+
+    /// Add an arbitrary object file to link in
+    pub fn object<P: AsRef<Path>>(&mut self, obj: P) -> &mut Build {
+        self.objects.push(obj.as_ref().to_path_buf());
+        self
+    }
+
+    /// Add an arbitrary flag to the invocation of the compiler
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .flag("-ffunction-sections")
+    ///     .compile("foo");
+    /// ```
+    pub fn flag(&mut self, flag: &str) -> &mut Build {
+        self.flags.push(flag.to_string());
+        self
+    }
+
+    /// Add a flag to the invocation of the ar
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .file("src/bar.c")
+    ///     .ar_flag("/NODEFAULTLIB:libc.dll")
+    ///     .compile("foo");
+    /// ```
+    pub fn ar_flag(&mut self, flag: &str) -> &mut Build {
+        self.ar_flags.push(flag.to_string());
+        self
+    }
+
+    /// Add a flag that will only be used with assembly files.
+    ///
+    /// The flag will be applied to input files with either a `.s` or
+    /// `.asm` extension (case insensitive).
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// cc::Build::new()
+    ///     .asm_flag("-Wa,-defsym,abc=1")
+    ///     .file("src/foo.S")  // The asm flag will be applied here
+    ///     .file("src/bar.c")  // The asm flag will not be applied here
+    ///     .compile("foo");
+    /// ```
+    pub fn asm_flag(&mut self, flag: &str) -> &mut Build {
+        self.asm_flags.push(flag.to_string());
+        self
+    }
+
+    fn ensure_check_file(&self) -> Result<PathBuf, Error> {
+        let out_dir = self.get_out_dir()?;
+        let src = if self.cuda {
+            assert!(self.cpp);
+            out_dir.join("flag_check.cu")
+        } else if self.cpp {
+            out_dir.join("flag_check.cpp")
+        } else {
+            out_dir.join("flag_check.c")
+        };
+
+        if !src.exists() {
+            let mut f = fs::File::create(&src)?;
+            write!(f, "int main(void) {{ return 0; }}")?;
+        }
+
+        Ok(src)
+    }
+
+    /// Run the compiler to test if it accepts the given flag.
+    ///
+    /// For a convenience method for setting flags conditionally,
+    /// see `flag_if_supported()`.
+    ///
+    /// It may return error if it's unable to run the compiler with a test file
+    /// (e.g. the compiler is missing or a write to the `out_dir` failed).
+    ///
+    /// Note: Once computed, the result of this call is stored in the
+    /// `known_flag_support` field. If `is_flag_supported(flag)`
+    /// is called again, the result will be read from the hash table.
+    pub fn is_flag_supported(&self, flag: &str) -> Result<bool, Error> {
+        let mut known_status = self.known_flag_support_status.lock().unwrap();
+        if let Some(is_supported) = known_status.get(flag).cloned() {
+            return Ok(is_supported);
+        }
+
+        let out_dir = self.get_out_dir()?;
+        let src = self.ensure_check_file()?;
+        let obj = out_dir.join("flag_check");
+        let target = self.get_target()?;
+        let host = self.get_host()?;
+        let mut cfg = Build::new();
+        cfg.flag(flag)
+            .target(&target)
+            .opt_level(0)
+            .host(&host)
+            .debug(false)
+            .cpp(self.cpp)
+            .cuda(self.cuda);
+        if let Some(ref c) = self.compiler {
+            cfg.compiler(c.clone());
+        }
+        let mut compiler = cfg.try_get_compiler()?;
+
+        // Clang uses stderr for verbose output, which yields a false positive
+        // result if the CFLAGS/CXXFLAGS include -v to aid in debugging.
+        if compiler.family.verbose_stderr() {
+            compiler.remove_arg("-v".into());
+        }
+
+        let mut cmd = compiler.to_command();
+        let is_arm = target.contains("aarch64") || target.contains("arm");
+        let clang = compiler.family == ToolFamily::Clang;
+        command_add_output_file(
+            &mut cmd,
+            &obj,
+            self.cuda,
+            target.contains("msvc"),
+            clang,
+            false,
+            is_arm,
+        );
+
+        // We need to explicitly tell msvc not to link and create an exe
+        // in the root directory of the crate
+        if target.contains("msvc") && !self.cuda {
+            cmd.arg("-c");
+        }
+
+        cmd.arg(&src);
+
+        let output = cmd.output()?;
+        let is_supported = output.status.success() && output.stderr.is_empty();
+
+        known_status.insert(flag.to_owned(), is_supported);
+        Ok(is_supported)
+    }
+
+    /// Add an arbitrary flag to the invocation of the compiler if it supports it
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .flag_if_supported("-Wlogical-op") // only supported by GCC
+    ///     .flag_if_supported("-Wunreachable-code") // only supported by clang
+    ///     .compile("foo");
+    /// ```
+    pub fn flag_if_supported(&mut self, flag: &str) -> &mut Build {
+        self.flags_supported.push(flag.to_string());
+        self
+    }
+
+    /// Set the `-shared` flag.
+    ///
+    /// When enabled, the compiler will produce a shared object which can
+    /// then be linked with other objects to form an executable.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .shared_flag(true)
+    ///     .compile("libfoo.so");
+    /// ```
+    pub fn shared_flag(&mut self, shared_flag: bool) -> &mut Build {
+        self.shared_flag = Some(shared_flag);
+        self
+    }
+
+    /// Set the `-static` flag.
+    ///
+    /// When enabled on systems that support dynamic linking, this prevents
+    /// linking with the shared libraries.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .shared_flag(true)
+    ///     .static_flag(true)
+    ///     .compile("foo");
+    /// ```
+    pub fn static_flag(&mut self, static_flag: bool) -> &mut Build {
+        self.static_flag = Some(static_flag);
+        self
+    }
+
+    /// Disables the generation of default compiler flags. The default compiler
+    /// flags may cause conflicts in some cross compiling scenarios.
+    ///
+    /// Setting the `CRATE_CC_NO_DEFAULTS` environment variable has the same
+    /// effect as setting this to `true`. The presence of the environment
+    /// variable and the value of `no_default_flags` will be OR'd together.
+    pub fn no_default_flags(&mut self, no_default_flags: bool) -> &mut Build {
+        self.no_default_flags = no_default_flags;
+        self
+    }
+
+    /// Add a file which will be compiled
+    pub fn file<P: AsRef<Path>>(&mut self, p: P) -> &mut Build {
+        self.files.push(p.as_ref().to_path_buf());
+        self
+    }
+
+    /// Add files which will be compiled
+    pub fn files<P>(&mut self, p: P) -> &mut Build
+    where
+        P: IntoIterator,
+        P::Item: AsRef<Path>,
+    {
+        for file in p.into_iter() {
+            self.file(file);
+        }
+        self
+    }
+
+    /// Set C++ support.
+    ///
+    /// The other `cpp_*` options will only become active if this is set to
+    /// `true`.
+    pub fn cpp(&mut self, cpp: bool) -> &mut Build {
+        self.cpp = cpp;
+        self
+    }
+
+    /// Set CUDA C++ support.
+    ///
+    /// Enabling CUDA will pass the detected C/C++ toolchain as an argument to
+    /// the CUDA compiler, NVCC. NVCC itself accepts some limited GNU-like args;
+    /// any other arguments for the C/C++ toolchain will be redirected using
+    /// "-Xcompiler" flags.
+    ///
+    /// If enabled, this also implicitly enables C++ support.
+    pub fn cuda(&mut self, cuda: bool) -> &mut Build {
+        self.cuda = cuda;
+        if cuda {
+            self.cpp = true;
+            self.cudart = Some("static".to_string());
+        }
+        self
+    }
+
+    /// Link CUDA run-time.
+    ///
+    /// This option mimics the `--cudart` NVCC command-line option. Just like
+    /// the original it accepts `{none|shared|static}`, with default being
+    /// `static`. The method has to be invoked after `.cuda(true)`, or not
+    /// at all, if the default is right for the project.
+    pub fn cudart(&mut self, cudart: &str) -> &mut Build {
+        if self.cuda {
+            self.cudart = Some(cudart.to_string());
+        }
+        self
+    }
+
+    /// Set warnings into errors flag.
+    ///
+    /// Disabled by default.
+    ///
+    /// Warning: turning warnings into errors only make sense
+    /// if you are a developer of the crate using cc-rs.
+    /// Some warnings only appear on some architecture or
+    /// specific version of the compiler. Any user of this crate,
+    /// or any other crate depending on it, could fail during
+    /// compile time.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .warnings_into_errors(true)
+    ///     .compile("libfoo.a");
+    /// ```
+    pub fn warnings_into_errors(&mut self, warnings_into_errors: bool) -> &mut Build {
+        self.warnings_into_errors = warnings_into_errors;
+        self
+    }
+
+    /// Set warnings flags.
+    ///
+    /// Adds some flags:
+    /// - "-Wall" for MSVC.
+    /// - "-Wall", "-Wextra" for GNU and Clang.
+    ///
+    /// Enabled by default.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .warnings(false)
+    ///     .compile("libfoo.a");
+    /// ```
+    pub fn warnings(&mut self, warnings: bool) -> &mut Build {
+        self.warnings = Some(warnings);
+        self.extra_warnings = Some(warnings);
+        self
+    }
+
+    /// Set extra warnings flags.
+    ///
+    /// Adds some flags:
+    /// - nothing for MSVC.
+    /// - "-Wextra" for GNU and Clang.
+    ///
+    /// Enabled by default.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// // Disables -Wextra, -Wall remains enabled:
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .extra_warnings(false)
+    ///     .compile("libfoo.a");
+    /// ```
+    pub fn extra_warnings(&mut self, warnings: bool) -> &mut Build {
+        self.extra_warnings = Some(warnings);
+        self
+    }
+
+    /// Set the standard library to link against when compiling with C++
+    /// support.
+    ///
+    /// See [`get_cpp_link_stdlib`](cc::Build::get_cpp_link_stdlib) documentation
+    /// for the default value.
+    /// If the `CXXSTDLIB` environment variable is set, its value will
+    /// override the default value, but not the value explicitly set by calling
+    /// this function.
+    ///
+    /// A value of `None` indicates that no automatic linking should happen,
+    /// otherwise cargo will link against the specified library.
+    ///
+    /// The given library name must not contain the `lib` prefix.
+    ///
+    /// Common values:
+    /// - `stdc++` for GNU
+    /// - `c++` for Clang
+    /// - `c++_shared` or `c++_static` for Android
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .shared_flag(true)
+    ///     .cpp_link_stdlib("stdc++")
+    ///     .compile("libfoo.so");
+    /// ```
+    pub fn cpp_link_stdlib<'a, V: Into<Option<&'a str>>>(
+        &mut self,
+        cpp_link_stdlib: V,
+    ) -> &mut Build {
+        self.cpp_link_stdlib = Some(cpp_link_stdlib.into().map(|s| s.into()));
+        self
+    }
+
+    /// Force the C++ compiler to use the specified standard library.
+    ///
+    /// Setting this option will automatically set `cpp_link_stdlib` to the same
+    /// value.
+    ///
+    /// The default value of this option is always `None`.
+    ///
+    /// This option has no effect when compiling for a Visual Studio based
+    /// target.
+    ///
+    /// This option sets the `-stdlib` flag, which is only supported by some
+    /// compilers (clang, icc) but not by others (gcc). The library will not
+    /// detect which compiler is used, as such it is the responsibility of the
+    /// caller to ensure that this option is only used in conjunction with a
+    /// compiler which supports the `-stdlib` flag.
+    ///
+    /// A value of `None` indicates that no specific C++ standard library should
+    /// be used, otherwise `-stdlib` is added to the compile invocation.
+    ///
+    /// The given library name must not contain the `lib` prefix.
+    ///
+    /// Common values:
+    /// - `stdc++` for GNU
+    /// - `c++` for Clang
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .cpp_set_stdlib("c++")
+    ///     .compile("libfoo.a");
+    /// ```
+    pub fn cpp_set_stdlib<'a, V: Into<Option<&'a str>>>(
+        &mut self,
+        cpp_set_stdlib: V,
+    ) -> &mut Build {
+        let cpp_set_stdlib = cpp_set_stdlib.into();
+        self.cpp_set_stdlib = cpp_set_stdlib.map(|s| s.into());
+        self.cpp_link_stdlib(cpp_set_stdlib);
+        self
+    }
+
+    /// Configures the target this configuration will be compiling for.
+    ///
+    /// This option is automatically scraped from the `TARGET` environment
+    /// variable by build scripts, so it's not required to call this function.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .target("aarch64-linux-android")
+    ///     .compile("foo");
+    /// ```
+    pub fn target(&mut self, target: &str) -> &mut Build {
+        self.target = Some(target.to_string());
+        self
+    }
+
+    /// Configures the host assumed by this configuration.
+    ///
+    /// This option is automatically scraped from the `HOST` environment
+    /// variable by build scripts, so it's not required to call this function.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// cc::Build::new()
+    ///     .file("src/foo.c")
+    ///     .host("arm-linux-gnueabihf")
+    ///     .compile("foo");
+    /// ```
+    pub fn host(&mut self, host: &str) -> &mut Build {
+        self.host = Some(host.to_string());
+        self
+    }
+
+    /// Configures the optimization level of the generated object files.
+    ///
+    /// This option is automatically scraped from the `OPT_LEVEL` environment
+    /// variable by build scripts, so it's not required to call this function.
+    pub fn opt_level(&mut self, opt_level: u32) -> &mut Build {
+        self.opt_level = Some(opt_level.to_string());
+        self
+    }
+
+    /// Configures the optimization level of the generated object files.
+    ///
+    /// This option is automatically scraped from the `OPT_LEVEL` environment
+    /// variable by build scripts, so it's not required to call this function.
+    pub fn opt_level_str(&mut self, opt_level: &str) -> &mut Build {
+        self.opt_level = Some(opt_level.to_string());
+        self
+    }
+
+    /// Configures whether the compiler will emit debug information when
+    /// generating object files.
+    ///
+    /// This option is automatically scraped from the `DEBUG` environment
+    /// variable by build scripts, so it's not required to call this function.
+    pub fn debug(&mut self, debug: bool) -> &mut Build {
+        self.debug = Some(debug);
+        self
+    }
+
+    /// Configures whether the compiler will emit instructions to store
+    /// frame pointers during codegen.
+    ///
+    /// This option is automatically enabled when debug information is emitted.
+    /// Otherwise the target platform compiler's default will be used.
+    /// You can use this option to force a specific setting.
+    pub fn force_frame_pointer(&mut self, force: bool) -> &mut Build {
+        self.force_frame_pointer = Some(force);
+        self
+    }
+
+    /// Configures the output directory where all object files and static
+    /// libraries will be located.
+    ///
+    /// This option is automatically scraped from the `OUT_DIR` environment
+    /// variable by build scripts, so it's not required to call this function.
+    pub fn out_dir<P: AsRef<Path>>(&mut self, out_dir: P) -> &mut Build {
+        self.out_dir = Some(out_dir.as_ref().to_owned());
+        self
+    }
+
+    /// Configures the compiler to be used to produce output.
+    ///
+    /// This option is automatically determined from the target platform or a
+    /// number of environment variables, so it's not required to call this
+    /// function.
+    pub fn compiler<P: AsRef<Path>>(&mut self, compiler: P) -> &mut Build {
+        self.compiler = Some(compiler.as_ref().to_owned());
+        self
+    }
+
+    /// Configures the tool used to assemble archives.
+    ///
+    /// This option is automatically determined from the target platform or a
+    /// number of environment variables, so it's not required to call this
+    /// function.
+    pub fn archiver<P: AsRef<Path>>(&mut self, archiver: P) -> &mut Build {
+        self.archiver = Some(archiver.as_ref().to_owned());
+        self
+    }
+
+    /// Configures the tool used to index archives.
+    ///
+    /// This option is automatically determined from the target platform or a
+    /// number of environment variables, so it's not required to call this
+    /// function.
+    pub fn ranlib<P: AsRef<Path>>(&mut self, ranlib: P) -> &mut Build {
+        self.ranlib = Some(ranlib.as_ref().to_owned());
+        self
+    }
+
+    /// Define whether metadata should be emitted for cargo allowing it to
+    /// automatically link the binary. Defaults to `true`.
+    ///
+    /// The emitted metadata is:
+    ///
+    ///  - `rustc-link-lib=static=`*compiled lib*
+    ///  - `rustc-link-search=native=`*target folder*
+    ///  - When target is MSVC, the ATL-MFC libs are added via `rustc-link-search=native=`
+    ///  - When C++ is enabled, the C++ stdlib is added via `rustc-link-lib`
+    ///  - If `emit_rerun_if_env_changed` is not `false`, `rerun-if-env-changed=`*env*
+    ///
+    pub fn cargo_metadata(&mut self, cargo_metadata: bool) -> &mut Build {
+        self.cargo_metadata = cargo_metadata;
+        self
+    }
+
+    /// Adds a native library modifier that will be added to the
+    /// `rustc-link-lib=static:MODIFIERS=LIBRARY_NAME` metadata line
+    /// emitted for cargo if `cargo_metadata` is enabled.
+    /// See https://doc.rust-lang.org/rustc/command-line-arguments.html#-l-link-the-generated-crate-to-a-native-library
+    /// for the list of modifiers accepted by rustc.
+    pub fn link_lib_modifier(&mut self, link_lib_modifier: &str) -> &mut Build {
+        self.link_lib_modifiers.push(link_lib_modifier.to_string());
+        self
+    }
+
+    /// Configures whether the compiler will emit position independent code.
+    ///
+    /// This option defaults to `false` for `windows-gnu` and bare metal targets and
+    /// to `true` for all other targets.
+    pub fn pic(&mut self, pic: bool) -> &mut Build {
+        self.pic = Some(pic);
+        self
+    }
+
+    /// Configures whether the Procedure Linkage Table is used for indirect
+    /// calls into shared libraries.
+    ///
+    /// The PLT is used to provide features like lazy binding, but introduces
+    /// a small performance loss due to extra pointer indirection. Setting
+    /// `use_plt` to `false` can provide a small performance increase.
+    ///
+    /// Note that skipping the PLT requires a recent version of GCC/Clang.
+    ///
+    /// This only applies to ELF targets. It has no effect on other platforms.
+    pub fn use_plt(&mut self, use_plt: bool) -> &mut Build {
+        self.use_plt = Some(use_plt);
+        self
+    }
+
+    /// Define whether metadata should be emitted for cargo to detect environment
+    /// changes that should trigger a rebuild.
+    ///
+    /// This has no effect if the `cargo_metadata` option is `false`.
+    ///
+    /// This option defaults to `true`.
+    pub fn emit_rerun_if_env_changed(&mut self, emit_rerun_if_env_changed: bool) -> &mut Build {
+        self.emit_rerun_if_env_changed = emit_rerun_if_env_changed;
+        self
+    }
+
+    /// Configures whether the /MT flag or the /MD flag will be passed to msvc build tools.
+    ///
+    /// This option defaults to `false`, and affect only msvc targets.
+    pub fn static_crt(&mut self, static_crt: bool) -> &mut Build {
+        self.static_crt = Some(static_crt);
+        self
+    }
+
+    #[doc(hidden)]
+    pub fn __set_env<A, B>(&mut self, a: A, b: B) -> &mut Build
+    where
+        A: AsRef<OsStr>,
+        B: AsRef<OsStr>,
+    {
+        self.env
+            .push((a.as_ref().to_owned(), b.as_ref().to_owned()));
+        self
+    }
+
+    /// Run the compiler, generating the file `output`
+    ///
+    /// This will return a result instead of panicing; see compile() for the complete description.
+    pub fn try_compile(&self, output: &str) -> Result<(), Error> {
+        let mut output_components = Path::new(output).components();
+        match (output_components.next(), output_components.next()) {
+            (Some(Component::Normal(_)), None) => {}
+            _ => {
+                return Err(Error::new(
+                    ErrorKind::InvalidArgument,
+                    "argument of `compile` must be a single normal path component",
+                ));
+            }
+        }
+
+        let (lib_name, gnu_lib_name) = if output.starts_with("lib") && output.ends_with(".a") {
+            (&output[3..output.len() - 2], output.to_owned())
+        } else {
+            let mut gnu = String::with_capacity(5 + output.len());
+            gnu.push_str("lib");
+            gnu.push_str(&output);
+            gnu.push_str(".a");
+            (output, gnu)
+        };
+        let dst = self.get_out_dir()?;
+
+        let mut objects = Vec::new();
+        for file in self.files.iter() {
+            let obj = if file.has_root() {
+                // If `file` is an absolute path, prefix the `basename`
+                // with the `dirname`'s hash to ensure name uniqueness.
+                let basename = file
+                    .file_name()
+                    .ok_or_else(|| Error::new(ErrorKind::InvalidArgument, "file_name() failure"))?
+                    .to_string_lossy();
+                let dirname = file
+                    .parent()
+                    .ok_or_else(|| Error::new(ErrorKind::InvalidArgument, "parent() failure"))?
+                    .to_string_lossy();
+                let mut hasher = hash_map::DefaultHasher::new();
+                hasher.write(dirname.to_string().as_bytes());
+                dst.join(format!("{:016x}-{}", hasher.finish(), basename))
+                    .with_extension("o")
+            } else {
+                dst.join(file).with_extension("o")
+            };
+            let obj = if !obj.starts_with(&dst) {
+                dst.join(obj.file_name().ok_or_else(|| {
+                    Error::new(ErrorKind::IOError, "Getting object file details failed.")
+                })?)
+            } else {
+                obj
+            };
+
+            match obj.parent() {
+                Some(s) => fs::create_dir_all(s)?,
+                None => {
+                    return Err(Error::new(
+                        ErrorKind::IOError,
+                        "Getting object file details failed.",
+                    ));
+                }
+            };
+
+            objects.push(Object::new(file.to_path_buf(), obj));
+        }
+        self.compile_objects(&objects)?;
+        self.assemble(lib_name, &dst.join(gnu_lib_name), &objects)?;
+
+        if self.get_target()?.contains("msvc") {
+            let compiler = self.get_base_compiler()?;
+            let atlmfc_lib = compiler
+                .env()
+                .iter()
+                .find(|&&(ref var, _)| var.as_os_str() == OsStr::new("LIB"))
+                .and_then(|&(_, ref lib_paths)| {
+                    env::split_paths(lib_paths).find(|path| {
+                        let sub = Path::new("atlmfc/lib");
+                        path.ends_with(sub) || path.parent().map_or(false, |p| p.ends_with(sub))
+                    })
+                });
+
+            if let Some(atlmfc_lib) = atlmfc_lib {
+                self.print(&format!(
+                    "cargo:rustc-link-search=native={}",
+                    atlmfc_lib.display()
+                ));
+            }
+        }
+
+        if self.link_lib_modifiers.is_empty() {
+            self.print(&format!("cargo:rustc-link-lib=static={}", lib_name));
+        } else {
+            let m = self.link_lib_modifiers.join(",");
+            self.print(&format!("cargo:rustc-link-lib=static:{}={}", m, lib_name));
+        }
+        self.print(&format!("cargo:rustc-link-search=native={}", dst.display()));
+
+        // Add specific C++ libraries, if enabled.
+        if self.cpp {
+            if let Some(stdlib) = self.get_cpp_link_stdlib()? {
+                self.print(&format!("cargo:rustc-link-lib={}", stdlib));
+            }
+        }
+
+        let cudart = match &self.cudart {
+            Some(opt) => opt.as_str(), // {none|shared|static}
+            None => "none",
+        };
+        if cudart != "none" {
+            if let Some(nvcc) = which(&self.get_compiler().path) {
+                // Try to figure out the -L search path. If it fails,
+                // it's on user to specify one by passing it through
+                // RUSTFLAGS environment variable.
+                let mut libtst = false;
+                let mut libdir = nvcc;
+                libdir.pop(); // remove 'nvcc'
+                libdir.push("..");
+                let target_arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap();
+                if cfg!(target_os = "linux") {
+                    libdir.push("targets");
+                    libdir.push(target_arch.to_owned() + "-linux");
+                    libdir.push("lib");
+                    libtst = true;
+                } else if cfg!(target_env = "msvc") {
+                    libdir.push("lib");
+                    match target_arch.as_str() {
+                        "x86_64" => {
+                            libdir.push("x64");
+                            libtst = true;
+                        }
+                        "x86" => {
+                            libdir.push("Win32");
+                            libtst = true;
+                        }
+                        _ => libtst = false,
+                    }
+                }
+                if libtst && libdir.is_dir() {
+                    println!(
+                        "cargo:rustc-link-search=native={}",
+                        libdir.to_str().unwrap()
+                    );
+                }
+
+                // And now the -l flag.
+                let lib = match cudart {
+                    "shared" => "cudart",
+                    "static" => "cudart_static",
+                    bad => panic!("unsupported cudart option: {}", bad),
+                };
+                println!("cargo:rustc-link-lib={}", lib);
+            }
+        }
+
+        Ok(())
+    }
+
+    /// Run the compiler, generating the file `output`
+    ///
+    /// # Library name
+    ///
+    /// The `output` string argument determines the file name for the compiled
+    /// library. The Rust compiler will create an assembly named "lib"+output+".a".
+    /// MSVC will create a file named output+".lib".
+    ///
+    /// The choice of `output` is close to arbitrary, but:
+    ///
+    /// - must be nonempty,
+    /// - must not contain a path separator (`/`),
+    /// - must be unique across all `compile` invocations made by the same build
+    ///   script.
+    ///
+    /// If your build script compiles a single source file, the base name of
+    /// that source file would usually be reasonable:
+    ///
+    /// ```no_run
+    /// cc::Build::new().file("blobstore.c").compile("blobstore");
+    /// ```
+    ///
+    /// Compiling multiple source files, some people use their crate's name, or
+    /// their crate's name + "-cc".
+    ///
+    /// Otherwise, please use your imagination.
+    ///
+    /// For backwards compatibility, if `output` starts with "lib" *and* ends
+    /// with ".a", a second "lib" prefix and ".a" suffix do not get added on,
+    /// but this usage is deprecated; please omit `lib` and `.a` in the argument
+    /// that you pass.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `output` is not formatted correctly or if one of the underlying
+    /// compiler commands fails. It can also panic if it fails reading file names
+    /// or creating directories.
+    pub fn compile(&self, output: &str) {
+        if let Err(e) = self.try_compile(output) {
+            fail(&e.message);
+        }
+    }
+
+    #[cfg(feature = "parallel")]
+    fn compile_objects<'me>(&'me self, objs: &[Object]) -> Result<(), Error> {
+        use std::sync::atomic::{AtomicBool, Ordering::SeqCst};
+        use std::sync::Once;
+
+        // Limit our parallelism globally with a jobserver. Start off by
+        // releasing our own token for this process so we can have a bit of an
+        // easier to write loop below. If this fails, though, then we're likely
+        // on Windows with the main implicit token, so we just have a bit extra
+        // parallelism for a bit and don't reacquire later.
+        let server = jobserver();
+        let reacquire = server.release_raw().is_ok();
+
+        // When compiling objects in parallel we do a few dirty tricks to speed
+        // things up:
+        //
+        // * First is that we use the `jobserver` crate to limit the parallelism
+        //   of this build script. The `jobserver` crate will use a jobserver
+        //   configured by Cargo for build scripts to ensure that parallelism is
+        //   coordinated across C compilations and Rust compilations. Before we
+        //   compile anything we make sure to wait until we acquire a token.
+        //
+        //   Note that this jobserver is cached globally so we only used one per
+        //   process and only worry about creating it once.
+        //
+        // * Next we use a raw `thread::spawn` per thread to actually compile
+        //   objects in parallel. We only actually spawn a thread after we've
+        //   acquired a token to perform some work
+        //
+        // * Finally though we want to keep the dependencies of this crate
+        //   pretty light, so we avoid using a safe abstraction like `rayon` and
+        //   instead rely on some bits of `unsafe` code. We know that this stack
+        //   frame persists while everything is compiling so we use all the
+        //   stack-allocated objects without cloning/reallocating. We use a
+        //   transmute to `State` with a `'static` lifetime to persist
+        //   everything we need across the boundary, and the join-on-drop
+        //   semantics of `JoinOnDrop` should ensure that our stack frame is
+        //   alive while threads are alive.
+        //
+        // With all that in mind we compile all objects in a loop here, after we
+        // acquire the appropriate tokens, Once all objects have been compiled
+        // we join on all the threads and propagate the results of compilation.
+        //
+        // Note that as a slight optimization we try to break out as soon as
+        // possible as soon as any compilation fails to ensure that errors get
+        // out to the user as fast as possible.
+        let error = AtomicBool::new(false);
+        let mut threads = Vec::new();
+        for obj in objs {
+            if error.load(SeqCst) {
+                break;
+            }
+            let token = server.acquire()?;
+            let state = State {
+                build: self,
+                obj,
+                error: &error,
+            };
+            let state = unsafe { std::mem::transmute::<State, State<'static>>(state) };
+            let thread = thread::spawn(|| {
+                let state: State<'me> = state; // erase the `'static` lifetime
+                let result = state.build.compile_object(state.obj);
+                if result.is_err() {
+                    state.error.store(true, SeqCst);
+                }
+                drop(token); // make sure our jobserver token is released after the compile
+                return result;
+            });
+            threads.push(JoinOnDrop(Some(thread)));
+        }
+
+        for mut thread in threads {
+            if let Some(thread) = thread.0.take() {
+                thread.join().expect("thread should not panic")?;
+            }
+        }
+
+        // Reacquire our process's token before we proceed, which we released
+        // before entering the loop above.
+        if reacquire {
+            server.acquire_raw()?;
+        }
+
+        return Ok(());
+
+        /// Shared state from the parent thread to the child thread. This
+        /// package of pointers is temporarily transmuted to a `'static`
+        /// lifetime to cross the thread boundary and then once the thread is
+        /// running we erase the `'static` to go back to an anonymous lifetime.
+        struct State<'a> {
+            build: &'a Build,
+            obj: &'a Object,
+            error: &'a AtomicBool,
+        }
+
+        /// Returns a suitable `jobserver::Client` used to coordinate
+        /// parallelism between build scripts.
+        fn jobserver() -> &'static jobserver::Client {
+            static INIT: Once = Once::new();
+            static mut JOBSERVER: Option<jobserver::Client> = None;
+
+            fn _assert_sync<T: Sync>() {}
+            _assert_sync::<jobserver::Client>();
+
+            unsafe {
+                INIT.call_once(|| {
+                    let server = default_jobserver();
+                    JOBSERVER = Some(server);
+                });
+                JOBSERVER.as_ref().unwrap()
+            }
+        }
+
+        unsafe fn default_jobserver() -> jobserver::Client {
+            // Try to use the environmental jobserver which Cargo typically
+            // initializes for us...
+            if let Some(client) = jobserver::Client::from_env() {
+                return client;
+            }
+
+            // ... but if that fails for whatever reason select something
+            // reasonable and crate a new jobserver. Use `NUM_JOBS` if set (it's
+            // configured by Cargo) and otherwise just fall back to a
+            // semi-reasonable number. Note that we could use `num_cpus` here
+            // but it's an extra dependency that will almost never be used, so
+            // it's generally not too worth it.
+            let mut parallelism = 4;
+            if let Ok(amt) = env::var("NUM_JOBS") {
+                if let Ok(amt) = amt.parse() {
+                    parallelism = amt;
+                }
+            }
+
+            // If we create our own jobserver then be sure to reserve one token
+            // for ourselves.
+            let client = jobserver::Client::new(parallelism).expect("failed to create jobserver");
+            client.acquire_raw().expect("failed to acquire initial");
+            return client;
+        }
+
+        struct JoinOnDrop(Option<thread::JoinHandle<Result<(), Error>>>);
+
+        impl Drop for JoinOnDrop {
+            fn drop(&mut self) {
+                if let Some(thread) = self.0.take() {
+                    drop(thread.join());
+                }
+            }
+        }
+    }
+
+    #[cfg(not(feature = "parallel"))]
+    fn compile_objects(&self, objs: &[Object]) -> Result<(), Error> {
+        for obj in objs {
+            self.compile_object(obj)?;
+        }
+        Ok(())
+    }
+
+    fn compile_object(&self, obj: &Object) -> Result<(), Error> {
+        let asm_ext = AsmFileExt::from_path(&obj.src);
+        let is_asm = asm_ext.is_some();
+        let target = self.get_target()?;
+        let msvc = target.contains("msvc");
+        let compiler = self.try_get_compiler()?;
+        let clang = compiler.family == ToolFamily::Clang;
+
+        let (mut cmd, name) = if msvc && asm_ext == Some(AsmFileExt::DotAsm) {
+            self.msvc_macro_assembler()?
+        } else {
+            let mut cmd = compiler.to_command();
+            for &(ref a, ref b) in self.env.iter() {
+                cmd.env(a, b);
+            }
+            (
+                cmd,
+                compiler
+                    .path
+                    .file_name()
+                    .ok_or_else(|| Error::new(ErrorKind::IOError, "Failed to get compiler path."))?
+                    .to_string_lossy()
+                    .into_owned(),
+            )
+        };
+        let is_arm = target.contains("aarch64") || target.contains("arm");
+        command_add_output_file(&mut cmd, &obj.dst, self.cuda, msvc, clang, is_asm, is_arm);
+        // armasm and armasm64 don't requrie -c option
+        if !msvc || !is_asm || !is_arm {
+            cmd.arg("-c");
+        }
+        if self.cuda && self.cuda_file_count() > 1 {
+            cmd.arg("--device-c");
+        }
+        if is_asm {
+            cmd.args(&self.asm_flags);
+        }
+        if compiler.family == (ToolFamily::Msvc { clang_cl: true }) && !is_asm {
+            // #513: For `clang-cl`, separate flags/options from the input file.
+            // When cross-compiling macOS -> Windows, this avoids interpreting
+            // common `/Users/...` paths as the `/U` flag and triggering
+            // `-Wslash-u-filename` warning.
+            cmd.arg("--");
+        }
+        cmd.arg(&obj.src);
+        if cfg!(target_os = "macos") {
+            self.fix_env_for_apple_os(&mut cmd)?;
+        }
+
+        run(&mut cmd, &name)?;
+        Ok(())
+    }
+
+    /// This will return a result instead of panicing; see expand() for the complete description.
+    pub fn try_expand(&self) -> Result<Vec<u8>, Error> {
+        let compiler = self.try_get_compiler()?;
+        let mut cmd = compiler.to_command();
+        for &(ref a, ref b) in self.env.iter() {
+            cmd.env(a, b);
+        }
+        cmd.arg("-E");
+
+        assert!(
+            self.files.len() <= 1,
+            "Expand may only be called for a single file"
+        );
+
+        for file in self.files.iter() {
+            cmd.arg(file);
+        }
+
+        let name = compiler
+            .path
+            .file_name()
+            .ok_or_else(|| Error::new(ErrorKind::IOError, "Failed to get compiler path."))?
+            .to_string_lossy()
+            .into_owned();
+
+        Ok(run_output(&mut cmd, &name)?)
+    }
+
+    /// Run the compiler, returning the macro-expanded version of the input files.
+    ///
+    /// This is only relevant for C and C++ files.
+    ///
+    /// # Panics
+    /// Panics if more than one file is present in the config, or if compiler
+    /// path has an invalid file name.
+    ///
+    /// # Example
+    /// ```no_run
+    /// let out = cc::Build::new().file("src/foo.c").expand();
+    /// ```
+    pub fn expand(&self) -> Vec<u8> {
+        match self.try_expand() {
+            Err(e) => fail(&e.message),
+            Ok(v) => v,
+        }
+    }
+
+    /// Get the compiler that's in use for this configuration.
+    ///
+    /// This function will return a `Tool` which represents the culmination
+    /// of this configuration at a snapshot in time. The returned compiler can
+    /// be inspected (e.g. the path, arguments, environment) to forward along to
+    /// other tools, or the `to_command` method can be used to invoke the
+    /// compiler itself.
+    ///
+    /// This method will take into account all configuration such as debug
+    /// information, optimization level, include directories, defines, etc.
+    /// Additionally, the compiler binary in use follows the standard
+    /// conventions for this path, e.g. looking at the explicitly set compiler,
+    /// environment variables (a number of which are inspected here), and then
+    /// falling back to the default configuration.
+    ///
+    /// # Panics
+    ///
+    /// Panics if an error occurred while determining the architecture.
+    pub fn get_compiler(&self) -> Tool {
+        match self.try_get_compiler() {
+            Ok(tool) => tool,
+            Err(e) => fail(&e.message),
+        }
+    }
+
+    /// Get the compiler that's in use for this configuration.
+    ///
+    /// This will return a result instead of panicing; see get_compiler() for the complete description.
+    pub fn try_get_compiler(&self) -> Result<Tool, Error> {
+        let opt_level = self.get_opt_level()?;
+        let target = self.get_target()?;
+
+        let mut cmd = self.get_base_compiler()?;
+        let envflags = self.envflags(if self.cpp { "CXXFLAGS" } else { "CFLAGS" });
+
+        // Disable default flag generation via `no_default_flags` or environment variable
+        let no_defaults = self.no_default_flags || self.getenv("CRATE_CC_NO_DEFAULTS").is_some();
+
+        if !no_defaults {
+            self.add_default_flags(&mut cmd, &target, &opt_level)?;
+        } else {
+            println!("Info: default compiler flags are disabled");
+        }
+
+        for arg in envflags {
+            cmd.push_cc_arg(arg.into());
+        }
+
+        for directory in self.include_directories.iter() {
+            cmd.args.push("-I".into());
+            cmd.args.push(directory.into());
+        }
+
+        // If warnings and/or extra_warnings haven't been explicitly set,
+        // then we set them only if the environment doesn't already have
+        // CFLAGS/CXXFLAGS, since those variables presumably already contain
+        // the desired set of warnings flags.
+
+        if self
+            .warnings
+            .unwrap_or(if self.has_flags() { false } else { true })
+        {
+            let wflags = cmd.family.warnings_flags().into();
+            cmd.push_cc_arg(wflags);
+        }
+
+        if self
+            .extra_warnings
+            .unwrap_or(if self.has_flags() { false } else { true })
+        {
+            if let Some(wflags) = cmd.family.extra_warnings_flags() {
+                cmd.push_cc_arg(wflags.into());
+            }
+        }
+
+        for flag in self.flags.iter() {
+            cmd.args.push(flag.into());
+        }
+
+        for flag in self.flags_supported.iter() {
+            if self.is_flag_supported(flag).unwrap_or(false) {
+                cmd.push_cc_arg(flag.into());
+            }
+        }
+
+        for &(ref key, ref value) in self.definitions.iter() {
+            if let Some(ref value) = *value {
+                cmd.args.push(format!("-D{}={}", key, value).into());
+            } else {
+                cmd.args.push(format!("-D{}", key).into());
+            }
+        }
+
+        if self.warnings_into_errors {
+            let warnings_to_errors_flag = cmd.family.warnings_to_errors_flag().into();
+            cmd.push_cc_arg(warnings_to_errors_flag);
+        }
+
+        Ok(cmd)
+    }
+
+    fn add_default_flags(
+        &self,
+        cmd: &mut Tool,
+        target: &str,
+        opt_level: &str,
+    ) -> Result<(), Error> {
+        // Non-target flags
+        // If the flag is not conditioned on target variable, it belongs here :)
+        match cmd.family {
+            ToolFamily::Msvc { .. } => {
+                cmd.push_cc_arg("-nologo".into());
+
+                let crt_flag = match self.static_crt {
+                    Some(true) => "-MT",
+                    Some(false) => "-MD",
+                    None => {
+                        let features = self
+                            .getenv("CARGO_CFG_TARGET_FEATURE")
+                            .unwrap_or(String::new());
+                        if features.contains("crt-static") {
+                            "-MT"
+                        } else {
+                            "-MD"
+                        }
+                    }
+                };
+                cmd.push_cc_arg(crt_flag.into());
+
+                match &opt_level[..] {
+                    // Msvc uses /O1 to enable all optimizations that minimize code size.
+                    "z" | "s" | "1" => cmd.push_opt_unless_duplicate("-O1".into()),
+                    // -O3 is a valid value for gcc and clang compilers, but not msvc. Cap to /O2.
+                    "2" | "3" => cmd.push_opt_unless_duplicate("-O2".into()),
+                    _ => {}
+                }
+            }
+            ToolFamily::Gnu | ToolFamily::Clang => {
+                // arm-linux-androideabi-gcc 4.8 shipped with Android NDK does
+                // not support '-Oz'
+                if opt_level == "z" && cmd.family != ToolFamily::Clang {
+                    cmd.push_opt_unless_duplicate("-Os".into());
+                } else {
+                    cmd.push_opt_unless_duplicate(format!("-O{}", opt_level).into());
+                }
+
+                if cmd.family == ToolFamily::Clang && target.contains("android") {
+                    // For compatibility with code that doesn't use pre-defined `__ANDROID__` macro.
+                    // If compiler used via ndk-build or cmake (officially supported build methods)
+                    // this macros is defined.
+                    // See https://android.googlesource.com/platform/ndk/+/refs/heads/ndk-release-r21/build/cmake/android.toolchain.cmake#456
+                    // https://android.googlesource.com/platform/ndk/+/refs/heads/ndk-release-r21/build/core/build-binary.mk#141
+                    cmd.push_opt_unless_duplicate("-DANDROID".into());
+                }
+
+                if !target.contains("apple-ios") && !target.contains("apple-watchos") {
+                    cmd.push_cc_arg("-ffunction-sections".into());
+                    cmd.push_cc_arg("-fdata-sections".into());
+                }
+                // Disable generation of PIC on bare-metal for now: rust-lld doesn't support this yet
+                if self.pic.unwrap_or(
+                    !target.contains("windows")
+                        && !target.contains("-none-")
+                        && !target.contains("uefi"),
+                ) {
+                    cmd.push_cc_arg("-fPIC".into());
+                    // PLT only applies if code is compiled with PIC support,
+                    // and only for ELF targets.
+                    if target.contains("linux") && !self.use_plt.unwrap_or(true) {
+                        cmd.push_cc_arg("-fno-plt".into());
+                    }
+                }
+            }
+        }
+
+        if self.get_debug() {
+            if self.cuda {
+                // NVCC debug flag
+                cmd.args.push("-G".into());
+            }
+            let family = cmd.family;
+            family.add_debug_flags(cmd, self.get_dwarf_version());
+        }
+
+        if self.get_force_frame_pointer() {
+            let family = cmd.family;
+            family.add_force_frame_pointer(cmd);
+        }
+
+        // Target flags
+        match cmd.family {
+            ToolFamily::Clang => {
+                if !(target.contains("android")
+                    && android_clang_compiler_uses_target_arg_internally(&cmd.path))
+                {
+                    if target.contains("darwin") {
+                        if let Some(arch) =
+                            map_darwin_target_from_rust_to_compiler_architecture(target)
+                        {
+                            cmd.args
+                                .push(format!("--target={}-apple-darwin", arch).into());
+                        }
+                    } else if target.contains("macabi") {
+                        if let Some(arch) =
+                            map_darwin_target_from_rust_to_compiler_architecture(target)
+                        {
+                            cmd.args
+                                .push(format!("--target={}-apple-ios-macabi", arch).into());
+                        }
+                    } else if target.contains("ios-sim") {
+                        if let Some(arch) =
+                            map_darwin_target_from_rust_to_compiler_architecture(target)
+                        {
+                            let deployment_target = env::var("IPHONEOS_DEPLOYMENT_TARGET")
+                                .unwrap_or_else(|_| "7.0".into());
+                            cmd.args.push(
+                                format!(
+                                    "--target={}-apple-ios{}-simulator",
+                                    arch, deployment_target
+                                )
+                                .into(),
+                            );
+                        }
+                    } else if target.contains("watchos-sim") {
+                        if let Some(arch) =
+                            map_darwin_target_from_rust_to_compiler_architecture(target)
+                        {
+                            let deployment_target = env::var("WATCHOS_DEPLOYMENT_TARGET")
+                                .unwrap_or_else(|_| "5.0".into());
+                            cmd.args.push(
+                                format!(
+                                    "--target={}-apple-watchos{}-simulator",
+                                    arch, deployment_target
+                                )
+                                .into(),
+                            );
+                        }
+                    } else if target.starts_with("riscv64gc-") {
+                        cmd.args.push(
+                            format!("--target={}", target.replace("riscv64gc", "riscv64")).into(),
+                        );
+                    } else if target.starts_with("riscv32gc-") {
+                        cmd.args.push(
+                            format!("--target={}", target.replace("riscv32gc", "riscv32")).into(),
+                        );
+                    } else if target.contains("uefi") {
+                        if target.contains("x86_64") {
+                            cmd.args.push("--target=x86_64-unknown-windows-gnu".into());
+                        } else if target.contains("i686") {
+                            cmd.args.push("--target=i686-unknown-windows-gnu".into())
+                        } else if target.contains("aarch64") {
+                            cmd.args.push("--target=aarch64-unknown-windows-gnu".into())
+                        }
+                    } else {
+                        cmd.push_cc_arg(format!("--target={}", target).into());
+                    }
+                }
+            }
+            ToolFamily::Msvc { clang_cl } => {
+                // This is an undocumented flag from MSVC but helps with making
+                // builds more reproducible by avoiding putting timestamps into
+                // files.
+                cmd.push_cc_arg("-Brepro".into());
+
+                if clang_cl {
+                    if target.contains("x86_64") {
+                        cmd.push_cc_arg("-m64".into());
+                    } else if target.contains("86") {
+                        cmd.push_cc_arg("-m32".into());
+                        cmd.push_cc_arg("-arch:IA32".into());
+                    } else {
+                        cmd.push_cc_arg(format!("--target={}", target).into());
+                    }
+                } else {
+                    if target.contains("i586") {
+                        cmd.push_cc_arg("-arch:IA32".into());
+                    }
+                }
+
+                // There is a check in corecrt.h that will generate a
+                // compilation error if
+                // _ARM_WINAPI_PARTITION_DESKTOP_SDK_AVAILABLE is
+                // not defined to 1. The check was added in Windows
+                // 8 days because only store apps were allowed on ARM.
+                // This changed with the release of Windows 10 IoT Core.
+                // The check will be going away in future versions of
+                // the SDK, but for all released versions of the
+                // Windows SDK it is required.
+                if target.contains("arm") || target.contains("thumb") {
+                    cmd.args
+                        .push("-D_ARM_WINAPI_PARTITION_DESKTOP_SDK_AVAILABLE=1".into());
+                }
+            }
+            ToolFamily::Gnu => {
+                if target.contains("i686") || target.contains("i586") {
+                    cmd.args.push("-m32".into());
+                } else if target == "x86_64-unknown-linux-gnux32" {
+                    cmd.args.push("-mx32".into());
+                } else if target.contains("x86_64") || target.contains("powerpc64") {
+                    cmd.args.push("-m64".into());
+                }
+
+                if target.contains("darwin") {
+                    if let Some(arch) = map_darwin_target_from_rust_to_compiler_architecture(target)
+                    {
+                        cmd.args.push("-arch".into());
+                        cmd.args.push(arch.into());
+                    }
+                }
+
+                if target.contains("-kmc-solid_") {
+                    cmd.args.push("-finput-charset=utf-8".into());
+                }
+
+                if self.static_flag.is_none() {
+                    let features = self
+                        .getenv("CARGO_CFG_TARGET_FEATURE")
+                        .unwrap_or(String::new());
+                    if features.contains("crt-static") {
+                        cmd.args.push("-static".into());
+                    }
+                }
+
+                // armv7 targets get to use armv7 instructions
+                if (target.starts_with("armv7") || target.starts_with("thumbv7"))
+                    && (target.contains("-linux-") || target.contains("-kmc-solid_"))
+                {
+                    cmd.args.push("-march=armv7-a".into());
+
+                    if target.ends_with("eabihf") {
+                        // lowest common denominator FPU
+                        cmd.args.push("-mfpu=vfpv3-d16".into());
+                    }
+                }
+
+                // (x86 Android doesn't say "eabi")
+                if target.contains("-androideabi") && target.contains("v7") {
+                    // -march=armv7-a handled above
+                    cmd.args.push("-mthumb".into());
+                    if !target.contains("neon") {
+                        // On android we can guarantee some extra float instructions
+                        // (specified in the android spec online)
+                        // NEON guarantees even more; see below.
+                        cmd.args.push("-mfpu=vfpv3-d16".into());
+                    }
+                    cmd.args.push("-mfloat-abi=softfp".into());
+                }
+
+                if target.contains("neon") {
+                    cmd.args.push("-mfpu=neon-vfpv4".into());
+                }
+
+                if target.starts_with("armv4t-unknown-linux-") {
+                    cmd.args.push("-march=armv4t".into());
+                    cmd.args.push("-marm".into());
+                    cmd.args.push("-mfloat-abi=soft".into());
+                }
+
+                if target.starts_with("armv5te-unknown-linux-") {
+                    cmd.args.push("-march=armv5te".into());
+                    cmd.args.push("-marm".into());
+                    cmd.args.push("-mfloat-abi=soft".into());
+                }
+
+                // For us arm == armv6 by default
+                if target.starts_with("arm-unknown-linux-") {
+                    cmd.args.push("-march=armv6".into());
+                    cmd.args.push("-marm".into());
+                    if target.ends_with("hf") {
+                        cmd.args.push("-mfpu=vfp".into());
+                    } else {
+                        cmd.args.push("-mfloat-abi=soft".into());
+                    }
+                }
+
+                // We can guarantee some settings for FRC
+                if target.starts_with("arm-frc-") {
+                    cmd.args.push("-march=armv7-a".into());
+                    cmd.args.push("-mcpu=cortex-a9".into());
+                    cmd.args.push("-mfpu=vfpv3".into());
+                    cmd.args.push("-mfloat-abi=softfp".into());
+                    cmd.args.push("-marm".into());
+                }
+
+                // Turn codegen down on i586 to avoid some instructions.
+                if target.starts_with("i586-unknown-linux-") {
+                    cmd.args.push("-march=pentium".into());
+                }
+
+                // Set codegen level for i686 correctly
+                if target.starts_with("i686-unknown-linux-") {
+                    cmd.args.push("-march=i686".into());
+                }
+
+                // Looks like `musl-gcc` makes it hard for `-m32` to make its way
+                // all the way to the linker, so we need to actually instruct the
+                // linker that we're generating 32-bit executables as well. This'll
+                // typically only be used for build scripts which transitively use
+                // these flags that try to compile executables.
+                if target == "i686-unknown-linux-musl" || target == "i586-unknown-linux-musl" {
+                    cmd.args.push("-Wl,-melf_i386".into());
+                }
+
+                if target.starts_with("thumb") {
+                    cmd.args.push("-mthumb".into());
+
+                    if target.ends_with("eabihf") {
+                        cmd.args.push("-mfloat-abi=hard".into())
+                    }
+                }
+                if target.starts_with("thumbv6m") {
+                    cmd.args.push("-march=armv6s-m".into());
+                }
+                if target.starts_with("thumbv7em") {
+                    cmd.args.push("-march=armv7e-m".into());
+
+                    if target.ends_with("eabihf") {
+                        cmd.args.push("-mfpu=fpv4-sp-d16".into())
+                    }
+                }
+                if target.starts_with("thumbv7m") {
+                    cmd.args.push("-march=armv7-m".into());
+                }
+                if target.starts_with("thumbv8m.base") {
+                    cmd.args.push("-march=armv8-m.base".into());
+                }
+                if target.starts_with("thumbv8m.main") {
+                    cmd.args.push("-march=armv8-m.main".into());
+
+                    if target.ends_with("eabihf") {
+                        cmd.args.push("-mfpu=fpv5-sp-d16".into())
+                    }
+                }
+                if target.starts_with("armebv7r") | target.starts_with("armv7r") {
+                    if target.starts_with("armeb") {
+                        cmd.args.push("-mbig-endian".into());
+                    } else {
+                        cmd.args.push("-mlittle-endian".into());
+                    }
+
+                    // ARM mode
+                    cmd.args.push("-marm".into());
+
+                    // R Profile
+                    cmd.args.push("-march=armv7-r".into());
+
+                    if target.ends_with("eabihf") {
+                        // Calling convention
+                        cmd.args.push("-mfloat-abi=hard".into());
+
+                        // lowest common denominator FPU
+                        // (see Cortex-R4 technical reference manual)
+                        cmd.args.push("-mfpu=vfpv3-d16".into())
+                    } else {
+                        // Calling convention
+                        cmd.args.push("-mfloat-abi=soft".into());
+                    }
+                }
+                if target.starts_with("armv7a") {
+                    cmd.args.push("-march=armv7-a".into());
+
+                    if target.ends_with("eabihf") {
+                        // lowest common denominator FPU
+                        cmd.args.push("-mfpu=vfpv3-d16".into());
+                    }
+                }
+                if target.starts_with("riscv32") || target.starts_with("riscv64") {
+                    // get the 32i/32imac/32imc/64gc/64imac/... part
+                    let mut parts = target.split('-');
+                    if let Some(arch) = parts.next() {
+                        let arch = &arch[5..];
+                        if target.contains("linux") && arch.starts_with("64") {
+                            cmd.args.push(("-march=rv64gc").into());
+                            cmd.args.push("-mabi=lp64d".into());
+                        } else if target.contains("freebsd") && arch.starts_with("64") {
+                            cmd.args.push(("-march=rv64gc").into());
+                            cmd.args.push("-mabi=lp64d".into());
+                        } else if target.contains("openbsd") && arch.starts_with("64") {
+                            cmd.args.push(("-march=rv64gc").into());
+                            cmd.args.push("-mabi=lp64d".into());
+                        } else if target.contains("linux") && arch.starts_with("32") {
+                            cmd.args.push(("-march=rv32gc").into());
+                            cmd.args.push("-mabi=ilp32d".into());
+                        } else if arch.starts_with("64") {
+                            cmd.args.push(("-march=rv".to_owned() + arch).into());
+                            cmd.args.push("-mabi=lp64".into());
+                        } else {
+                            cmd.args.push(("-march=rv".to_owned() + arch).into());
+                            cmd.args.push("-mabi=ilp32".into());
+                        }
+                        cmd.args.push("-mcmodel=medany".into());
+                    }
+                }
+            }
+        }
+
+        if target.contains("apple-ios") || target.contains("apple-watchos") {
+            self.ios_watchos_flags(cmd)?;
+        }
+
+        if self.static_flag.unwrap_or(false) {
+            cmd.args.push("-static".into());
+        }
+        if self.shared_flag.unwrap_or(false) {
+            cmd.args.push("-shared".into());
+        }
+
+        if self.cpp {
+            match (self.cpp_set_stdlib.as_ref(), cmd.family) {
+                (None, _) => {}
+                (Some(stdlib), ToolFamily::Gnu) | (Some(stdlib), ToolFamily::Clang) => {
+                    cmd.push_cc_arg(format!("-stdlib=lib{}", stdlib).into());
+                }
+                _ => {
+                    println!(
+                        "cargo:warning=cpp_set_stdlib is specified, but the {:?} compiler \
+                         does not support this option, ignored",
+                        cmd.family
+                    );
+                }
+            }
+        }
+
+        Ok(())
+    }
+
+    fn has_flags(&self) -> bool {
+        let flags_env_var_name = if self.cpp { "CXXFLAGS" } else { "CFLAGS" };
+        let flags_env_var_value = self.get_var(flags_env_var_name);
+        if let Ok(_) = flags_env_var_value {
+            true
+        } else {
+            false
+        }
+    }
+
+    fn msvc_macro_assembler(&self) -> Result<(Command, String), Error> {
+        let target = self.get_target()?;
+        let tool = if target.contains("x86_64") {
+            "ml64.exe"
+        } else if target.contains("arm") {
+            "armasm.exe"
+        } else if target.contains("aarch64") {
+            "armasm64.exe"
+        } else {
+            "ml.exe"
+        };
+        let mut cmd = windows_registry::find(&target, tool).unwrap_or_else(|| self.cmd(tool));
+        cmd.arg("-nologo"); // undocumented, yet working with armasm[64]
+        for directory in self.include_directories.iter() {
+            cmd.arg("-I").arg(directory);
+        }
+        if target.contains("aarch64") || target.contains("arm") {
+            if self.get_debug() {
+                cmd.arg("-g");
+            }
+
+            println!("cargo:warning=The MSVC ARM assemblers do not support -D flags");
+        } else {
+            if self.get_debug() {
+                cmd.arg("-Zi");
+            }
+
+            for &(ref key, ref value) in self.definitions.iter() {
+                if let Some(ref value) = *value {
+                    cmd.arg(&format!("-D{}={}", key, value));
+                } else {
+                    cmd.arg(&format!("-D{}", key));
+                }
+            }
+        }
+
+        if target.contains("i686") || target.contains("i586") {
+            cmd.arg("-safeseh");
+        }
+        for flag in self.flags.iter() {
+            cmd.arg(flag);
+        }
+
+        Ok((cmd, tool.to_string()))
+    }
+
+    fn assemble(&self, lib_name: &str, dst: &Path, objs: &[Object]) -> Result<(), Error> {
+        // Delete the destination if it exists as we want to
+        // create on the first iteration instead of appending.
+        let _ = fs::remove_file(&dst);
+
+        // Add objects to the archive in limited-length batches. This helps keep
+        // the length of the command line within a reasonable length to avoid
+        // blowing system limits on limiting platforms like Windows.
+        let objs: Vec<_> = objs
+            .iter()
+            .map(|o| o.dst.clone())
+            .chain(self.objects.clone())
+            .collect();
+        for chunk in objs.chunks(100) {
+            self.assemble_progressive(dst, chunk)?;
+        }
+
+        if self.cuda && self.cuda_file_count() > 0 {
+            // Link the device-side code and add it to the target library,
+            // so that non-CUDA linker can link the final binary.
+
+            let out_dir = self.get_out_dir()?;
+            let dlink = out_dir.join(lib_name.to_owned() + "_dlink.o");
+            let mut nvcc = self.get_compiler().to_command();
+            nvcc.arg("--device-link")
+                .arg("-o")
+                .arg(dlink.clone())
+                .arg(dst);
+            run(&mut nvcc, "nvcc")?;
+            self.assemble_progressive(dst, &[dlink])?;
+        }
+
+        let target = self.get_target()?;
+        if target.contains("msvc") {
+            // The Rust compiler will look for libfoo.a and foo.lib, but the
+            // MSVC linker will also be passed foo.lib, so be sure that both
+            // exist for now.
+
+            let lib_dst = dst.with_file_name(format!("{}.lib", lib_name));
+            let _ = fs::remove_file(&lib_dst);
+            match fs::hard_link(&dst, &lib_dst).or_else(|_| {
+                // if hard-link fails, just copy (ignoring the number of bytes written)
+                fs::copy(&dst, &lib_dst).map(|_| ())
+            }) {
+                Ok(_) => (),
+                Err(_) => {
+                    return Err(Error::new(
+                        ErrorKind::IOError,
+                        "Could not copy or create a hard-link to the generated lib file.",
+                    ));
+                }
+            };
+        } else {
+            // Non-msvc targets (those using `ar`) need a separate step to add
+            // the symbol table to archives since our construction command of
+            // `cq` doesn't add it for us.
+            let (mut ar, cmd, _any_flags) = self.get_ar()?;
+
+            // NOTE: We add `s` even if flags were passed using $ARFLAGS/ar_flag, because `s`
+            // here represents a _mode_, not an arbitrary flag. Further discussion of this choice
+            // can be seen in https://github.com/rust-lang/cc-rs/pull/763.
+            run(ar.arg("s").arg(dst), &cmd)?;
+        }
+
+        Ok(())
+    }
+
+    fn assemble_progressive(&self, dst: &Path, objs: &[PathBuf]) -> Result<(), Error> {
+        let target = self.get_target()?;
+
+        if target.contains("msvc") {
+            let (mut cmd, program, any_flags) = self.get_ar()?;
+            // NOTE: -out: here is an I/O flag, and so must be included even if $ARFLAGS/ar_flag is
+            // in use. -nologo on the other hand is just a regular flag, and one that we'll skip if
+            // the caller has explicitly dictated the flags they want. See
+            // https://github.com/rust-lang/cc-rs/pull/763 for further discussion.
+            let mut out = OsString::from("-out:");
+            out.push(dst);
+            cmd.arg(out);
+            if !any_flags {
+                cmd.arg("-nologo");
+            }
+            // If the library file already exists, add the library name
+            // as an argument to let lib.exe know we are appending the objs.
+            if dst.exists() {
+                cmd.arg(dst);
+            }
+            cmd.args(objs);
+            run(&mut cmd, &program)?;
+        } else {
+            let (mut ar, cmd, _any_flags) = self.get_ar()?;
+
+            // Set an environment variable to tell the OSX archiver to ensure
+            // that all dates listed in the archive are zero, improving
+            // determinism of builds. AFAIK there's not really official
+            // documentation of this but there's a lot of references to it if
+            // you search google.
+            //
+            // You can reproduce this locally on a mac with:
+            //
+            //      $ touch foo.c
+            //      $ cc -c foo.c -o foo.o
+            //
+            //      # Notice that these two checksums are different
+            //      $ ar crus libfoo1.a foo.o && sleep 2 && ar crus libfoo2.a foo.o
+            //      $ md5sum libfoo*.a
+            //
+            //      # Notice that these two checksums are the same
+            //      $ export ZERO_AR_DATE=1
+            //      $ ar crus libfoo1.a foo.o && sleep 2 && touch foo.o && ar crus libfoo2.a foo.o
+            //      $ md5sum libfoo*.a
+            //
+            // In any case if this doesn't end up getting read, it shouldn't
+            // cause that many issues!
+            ar.env("ZERO_AR_DATE", "1");
+
+            // NOTE: We add cq here regardless of whether $ARFLAGS/ar_flag have been used because
+            // it dictates the _mode_ ar runs in, which the setter of $ARFLAGS/ar_flag can't
+            // dictate. See https://github.com/rust-lang/cc-rs/pull/763 for further discussion.
+            run(ar.arg("cq").arg(dst).args(objs), &cmd)?;
+        }
+
+        Ok(())
+    }
+
+    fn ios_watchos_flags(&self, cmd: &mut Tool) -> Result<(), Error> {
+        enum ArchSpec {
+            Device(&'static str),
+            Simulator(&'static str),
+            Catalyst(&'static str),
+        }
+
+        enum Os {
+            Ios,
+            WatchOs,
+        }
+        impl Display for Os {
+            fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+                match self {
+                    Os::Ios => f.write_str("iOS"),
+                    Os::WatchOs => f.write_str("WatchOS"),
+                }
+            }
+        }
+
+        let target = self.get_target()?;
+        let os = if target.contains("-watchos") {
+            Os::WatchOs
+        } else {
+            Os::Ios
+        };
+
+        let arch = target.split('-').nth(0).ok_or_else(|| {
+            Error::new(
+                ErrorKind::ArchitectureInvalid,
+                format!("Unknown architecture for {} target.", os).as_str(),
+            )
+        })?;
+
+        let is_catalyst = match target.split('-').nth(3) {
+            Some(v) => v == "macabi",
+            None => false,
+        };
+
+        let is_sim = match target.split('-').nth(3) {
+            Some(v) => v == "sim",
+            None => false,
+        };
+
+        let arch = if is_catalyst {
+            match arch {
+                "arm64e" => ArchSpec::Catalyst("arm64e"),
+                "arm64" | "aarch64" => ArchSpec::Catalyst("arm64"),
+                "x86_64" => ArchSpec::Catalyst("-m64"),
+                _ => {
+                    return Err(Error::new(
+                        ErrorKind::ArchitectureInvalid,
+                        "Unknown architecture for iOS target.",
+                    ));
+                }
+            }
+        } else if is_sim {
+            match arch {
+                "arm64" | "aarch64" => ArchSpec::Simulator("arm64"),
+                "x86_64" => ArchSpec::Simulator("-m64"),
+                _ => {
+                    return Err(Error::new(
+                        ErrorKind::ArchitectureInvalid,
+                        "Unknown architecture for iOS simulator target.",
+                    ));
+                }
+            }
+        } else {
+            match arch {
+                "arm" | "armv7" | "thumbv7" => ArchSpec::Device("armv7"),
+                "armv7k" => ArchSpec::Device("armv7k"),
+                "armv7s" | "thumbv7s" => ArchSpec::Device("armv7s"),
+                "arm64e" => ArchSpec::Device("arm64e"),
+                "arm64" | "aarch64" => ArchSpec::Device("arm64"),
+                "arm64_32" => ArchSpec::Device("arm64_32"),
+                "i386" | "i686" => ArchSpec::Simulator("-m32"),
+                "x86_64" => ArchSpec::Simulator("-m64"),
+                _ => {
+                    return Err(Error::new(
+                        ErrorKind::ArchitectureInvalid,
+                        format!("Unknown architecture for {} target.", os).as_str(),
+                    ));
+                }
+            }
+        };
+
+        let (sdk_prefix, sim_prefix, min_version) = match os {
+            Os::Ios => (
+                "iphone",
+                "ios-",
+                std::env::var("IPHONEOS_DEPLOYMENT_TARGET").unwrap_or_else(|_| "7.0".into()),
+            ),
+            Os::WatchOs => (
+                "watch",
+                "watch",
+                std::env::var("WATCHOS_DEPLOYMENT_TARGET").unwrap_or_else(|_| "2.0".into()),
+            ),
+        };
+
+        let sdk = match arch {
+            ArchSpec::Device(arch) => {
+                cmd.args.push("-arch".into());
+                cmd.args.push(arch.into());
+                cmd.args
+                    .push(format!("-m{}os-version-min={}", sdk_prefix, min_version).into());
+                format!("{}os", sdk_prefix)
+            }
+            ArchSpec::Simulator(arch) => {
+                if arch.starts_with('-') {
+                    // -m32 or -m64
+                    cmd.args.push(arch.into());
+                } else {
+                    cmd.args.push("-arch".into());
+                    cmd.args.push(arch.into());
+                }
+                cmd.args
+                    .push(format!("-m{}simulator-version-min={}", sim_prefix, min_version).into());
+                format!("{}simulator", sdk_prefix)
+            }
+            ArchSpec::Catalyst(_) => "macosx".to_owned(),
+        };
+
+        self.print(&format!("Detecting {} SDK path for {}", os, sdk));
+        let sdk_path = if let Some(sdkroot) = env::var_os("SDKROOT") {
+            sdkroot
+        } else {
+            self.apple_sdk_root(sdk.as_str())?
+        };
+
+        cmd.args.push("-isysroot".into());
+        cmd.args.push(sdk_path);
+        // TODO: Remove this once Apple stops accepting apps built with Xcode 13
+        cmd.args.push("-fembed-bitcode".into());
+
+        Ok(())
+    }
+
+    fn cmd<P: AsRef<OsStr>>(&self, prog: P) -> Command {
+        let mut cmd = Command::new(prog);
+        for &(ref a, ref b) in self.env.iter() {
+            cmd.env(a, b);
+        }
+        cmd
+    }
+
+    fn get_base_compiler(&self) -> Result<Tool, Error> {
+        if let Some(ref c) = self.compiler {
+            return Ok(Tool::new(c.clone()));
+        }
+        let host = self.get_host()?;
+        let target = self.get_target()?;
+        let (env, msvc, gnu, traditional, clang) = if self.cpp {
+            ("CXX", "cl.exe", "g++", "c++", "clang++")
+        } else {
+            ("CC", "cl.exe", "gcc", "cc", "clang")
+        };
+
+        // On historical Solaris systems, "cc" may have been Sun Studio, which
+        // is not flag-compatible with "gcc".  This history casts a long shadow,
+        // and many modern illumos distributions today ship GCC as "gcc" without
+        // also making it available as "cc".
+        let default = if host.contains("solaris") || host.contains("illumos") {
+            gnu
+        } else {
+            traditional
+        };
+
+        let cl_exe = windows_registry::find_tool(&target, "cl.exe");
+
+        let tool_opt: Option<Tool> = self
+            .env_tool(env)
+            .map(|(tool, wrapper, args)| {
+                // find the driver mode, if any
+                const DRIVER_MODE: &str = "--driver-mode=";
+                let driver_mode = args
+                    .iter()
+                    .find(|a| a.starts_with(DRIVER_MODE))
+                    .map(|a| &a[DRIVER_MODE.len()..]);
+                // Chop off leading/trailing whitespace to work around
+                // semi-buggy build scripts which are shared in
+                // makefiles/configure scripts (where spaces are far more
+                // lenient)
+                let mut t = Tool::with_clang_driver(PathBuf::from(tool.trim()), driver_mode);
+                if let Some(cc_wrapper) = wrapper {
+                    t.cc_wrapper_path = Some(PathBuf::from(cc_wrapper));
+                }
+                for arg in args {
+                    t.cc_wrapper_args.push(arg.into());
+                }
+                t
+            })
+            .or_else(|| {
+                if target.contains("emscripten") {
+                    let tool = if self.cpp { "em++" } else { "emcc" };
+                    // Windows uses bat file so we have to be a bit more specific
+                    if cfg!(windows) {
+                        let mut t = Tool::new(PathBuf::from("cmd"));
+                        t.args.push("/c".into());
+                        t.args.push(format!("{}.bat", tool).into());
+                        Some(t)
+                    } else {
+                        Some(Tool::new(PathBuf::from(tool)))
+                    }
+                } else {
+                    None
+                }
+            })
+            .or_else(|| cl_exe.clone());
+
+        let tool = match tool_opt {
+            Some(t) => t,
+            None => {
+                let compiler = if host.contains("windows") && target.contains("windows") {
+                    if target.contains("msvc") {
+                        msvc.to_string()
+                    } else {
+                        let cc = if target.contains("llvm") { clang } else { gnu };
+                        format!("{}.exe", cc)
+                    }
+                } else if target.contains("apple-ios") {
+                    clang.to_string()
+                } else if target.contains("apple-watchos") {
+                    clang.to_string()
+                } else if target.contains("android") {
+                    autodetect_android_compiler(&target, &host, gnu, clang)
+                } else if target.contains("cloudabi") {
+                    format!("{}-{}", target, traditional)
+                } else if target == "wasm32-wasi"
+                    || target == "wasm32-unknown-wasi"
+                    || target == "wasm32-unknown-unknown"
+                {
+                    "clang".to_string()
+                } else if target.contains("vxworks") {
+                    if self.cpp {
+                        "wr-c++".to_string()
+                    } else {
+                        "wr-cc".to_string()
+                    }
+                } else if target.starts_with("armv7a-kmc-solid_") {
+                    format!("arm-kmc-eabi-{}", gnu)
+                } else if target.starts_with("aarch64-kmc-solid_") {
+                    format!("aarch64-kmc-elf-{}", gnu)
+                } else if self.get_host()? != target {
+                    let prefix = self.prefix_for_target(&target);
+                    match prefix {
+                        Some(prefix) => {
+                            let cc = if target.contains("llvm") { clang } else { gnu };
+                            format!("{}-{}", prefix, cc)
+                        }
+                        None => default.to_string(),
+                    }
+                } else {
+                    default.to_string()
+                };
+
+                let mut t = Tool::new(PathBuf::from(compiler));
+                if let Some(cc_wrapper) = Self::rustc_wrapper_fallback() {
+                    t.cc_wrapper_path = Some(PathBuf::from(cc_wrapper));
+                }
+                t
+            }
+        };
+
+        let mut tool = if self.cuda {
+            assert!(
+                tool.args.is_empty(),
+                "CUDA compilation currently assumes empty pre-existing args"
+            );
+            let nvcc = match self.get_var("NVCC") {
+                Err(_) => "nvcc".into(),
+                Ok(nvcc) => nvcc,
+            };
+            let mut nvcc_tool = Tool::with_features(PathBuf::from(nvcc), None, self.cuda);
+            nvcc_tool
+                .args
+                .push(format!("-ccbin={}", tool.path.display()).into());
+            nvcc_tool.family = tool.family;
+            nvcc_tool
+        } else {
+            tool
+        };
+
+        // New "standalone" C/C++ cross-compiler executables from recent Android NDK
+        // are just shell scripts that call main clang binary (from Android NDK) with
+        // proper `--target` argument.
+        //
+        // For example, armv7a-linux-androideabi16-clang passes
+        // `--target=armv7a-linux-androideabi16` to clang.
+        //
+        // As the shell script calls the main clang binary, the command line limit length
+        // on Windows is restricted to around 8k characters instead of around 32k characters.
+        // To remove this limit, we call the main clang binary directly and construct the
+        // `--target=` ourselves.
+        if host.contains("windows") && android_clang_compiler_uses_target_arg_internally(&tool.path)
+        {
+            if let Some(path) = tool.path.file_name() {
+                let file_name = path.to_str().unwrap().to_owned();
+                let (target, clang) = file_name.split_at(file_name.rfind("-").unwrap());
+
+                tool.path.set_file_name(clang.trim_start_matches("-"));
+                tool.path.set_extension("exe");
+                tool.args.push(format!("--target={}", target).into());
+
+                // Additionally, shell scripts for target i686-linux-android versions 16 to 24
+                // pass the `mstackrealign` option so we do that here as well.
+                if target.contains("i686-linux-android") {
+                    let (_, version) = target.split_at(target.rfind("d").unwrap() + 1);
+                    if let Ok(version) = version.parse::<u32>() {
+                        if version > 15 && version < 25 {
+                            tool.args.push("-mstackrealign".into());
+                        }
+                    }
+                }
+            };
+        }
+
+        // If we found `cl.exe` in our environment, the tool we're returning is
+        // an MSVC-like tool, *and* no env vars were set then set env vars for
+        // the tool that we're returning.
+        //
+        // Env vars are needed for things like `link.exe` being put into PATH as
+        // well as header include paths sometimes. These paths are automatically
+        // included by default but if the `CC` or `CXX` env vars are set these
+        // won't be used. This'll ensure that when the env vars are used to
+        // configure for invocations like `clang-cl` we still get a "works out
+        // of the box" experience.
+        if let Some(cl_exe) = cl_exe {
+            if tool.family == (ToolFamily::Msvc { clang_cl: true })
+                && tool.env.len() == 0
+                && target.contains("msvc")
+            {
+                for &(ref k, ref v) in cl_exe.env.iter() {
+                    tool.env.push((k.to_owned(), v.to_owned()));
+                }
+            }
+        }
+
+        Ok(tool)
+    }
+
+    fn get_var(&self, var_base: &str) -> Result<String, Error> {
+        let target = self.get_target()?;
+        let host = self.get_host()?;
+        let kind = if host == target { "HOST" } else { "TARGET" };
+        let target_u = target.replace("-", "_");
+        let res = self
+            .getenv(&format!("{}_{}", var_base, target))
+            .or_else(|| self.getenv(&format!("{}_{}", var_base, target_u)))
+            .or_else(|| self.getenv(&format!("{}_{}", kind, var_base)))
+            .or_else(|| self.getenv(var_base));
+
+        match res {
+            Some(res) => Ok(res),
+            None => Err(Error::new(
+                ErrorKind::EnvVarNotFound,
+                &format!("Could not find environment variable {}.", var_base),
+            )),
+        }
+    }
+
+    fn envflags(&self, name: &str) -> Vec<String> {
+        self.get_var(name)
+            .unwrap_or(String::new())
+            .split_ascii_whitespace()
+            .map(|slice| slice.to_string())
+            .collect()
+    }
+
+    /// Returns a fallback `cc_compiler_wrapper` by introspecting `RUSTC_WRAPPER`
+    fn rustc_wrapper_fallback() -> Option<String> {
+        // No explicit CC wrapper was detected, but check if RUSTC_WRAPPER
+        // is defined and is a build accelerator that is compatible with
+        // C/C++ compilers (e.g. sccache)
+        const VALID_WRAPPERS: &[&'static str] = &["sccache", "cachepot"];
+
+        let rustc_wrapper = std::env::var_os("RUSTC_WRAPPER")?;
+        let wrapper_path = Path::new(&rustc_wrapper);
+        let wrapper_stem = wrapper_path.file_stem()?;
+
+        if VALID_WRAPPERS.contains(&wrapper_stem.to_str()?) {
+            Some(rustc_wrapper.to_str()?.to_owned())
+        } else {
+            None
+        }
+    }
+
+    /// Returns compiler path, optional modifier name from whitelist, and arguments vec
+    fn env_tool(&self, name: &str) -> Option<(String, Option<String>, Vec<String>)> {
+        let tool = match self.get_var(name) {
+            Ok(tool) => tool,
+            Err(_) => return None,
+        };
+
+        // If this is an exact path on the filesystem we don't want to do any
+        // interpretation at all, just pass it on through. This'll hopefully get
+        // us to support spaces-in-paths.
+        if Path::new(&tool).exists() {
+            return Some((tool, None, Vec::new()));
+        }
+
+        // Ok now we want to handle a couple of scenarios. We'll assume from
+        // here on out that spaces are splitting separate arguments. Two major
+        // features we want to support are:
+        //
+        //      CC='sccache cc'
+        //
+        // aka using `sccache` or any other wrapper/caching-like-thing for
+        // compilations. We want to know what the actual compiler is still,
+        // though, because our `Tool` API support introspection of it to see
+        // what compiler is in use.
+        //
+        // additionally we want to support
+        //
+        //      CC='cc -flag'
+        //
+        // where the CC env var is used to also pass default flags to the C
+        // compiler.
+        //
+        // It's true that everything here is a bit of a pain, but apparently if
+        // you're not literally make or bash then you get a lot of bug reports.
+        let known_wrappers = ["ccache", "distcc", "sccache", "icecc", "cachepot"];
+
+        let mut parts = tool.split_whitespace();
+        let maybe_wrapper = match parts.next() {
+            Some(s) => s,
+            None => return None,
+        };
+
+        let file_stem = Path::new(maybe_wrapper)
+            .file_stem()
+            .unwrap()
+            .to_str()
+            .unwrap();
+        if known_wrappers.contains(&file_stem) {
+            if let Some(compiler) = parts.next() {
+                return Some((
+                    compiler.to_string(),
+                    Some(maybe_wrapper.to_string()),
+                    parts.map(|s| s.to_string()).collect(),
+                ));
+            }
+        }
+
+        Some((
+            maybe_wrapper.to_string(),
+            Self::rustc_wrapper_fallback(),
+            parts.map(|s| s.to_string()).collect(),
+        ))
+    }
+
+    /// Returns the C++ standard library:
+    /// 1. If [cpp_link_stdlib](cc::Build::cpp_link_stdlib) is set, uses its value.
+    /// 2. Else if the `CXXSTDLIB` environment variable is set, uses its value.
+    /// 3. Else the default is `libc++` for OS X and BSDs, `libc++_shared` for Android,
+    /// `None` for MSVC and `libstdc++` for anything else.
+    fn get_cpp_link_stdlib(&self) -> Result<Option<String>, Error> {
+        match self.cpp_link_stdlib.clone() {
+            Some(s) => Ok(s),
+            None => {
+                if let Ok(stdlib) = self.get_var("CXXSTDLIB") {
+                    if stdlib.is_empty() {
+                        Ok(None)
+                    } else {
+                        Ok(Some(stdlib))
+                    }
+                } else {
+                    let target = self.get_target()?;
+                    if target.contains("msvc") {
+                        Ok(None)
+                    } else if target.contains("apple") {
+                        Ok(Some("c++".to_string()))
+                    } else if target.contains("freebsd") {
+                        Ok(Some("c++".to_string()))
+                    } else if target.contains("openbsd") {
+                        Ok(Some("c++".to_string()))
+                    } else if target.contains("android") {
+                        Ok(Some("c++_shared".to_string()))
+                    } else {
+                        Ok(Some("stdc++".to_string()))
+                    }
+                }
+            }
+        }
+    }
+
+    fn get_ar(&self) -> Result<(Command, String, bool), Error> {
+        self.try_get_archiver_and_flags()
+    }
+
+    /// Get the archiver (ar) that's in use for this configuration.
+    ///
+    /// You can use [`Command::get_program`] to get just the path to the command.
+    ///
+    /// This method will take into account all configuration such as debug
+    /// information, optimization level, include directories, defines, etc.
+    /// Additionally, the compiler binary in use follows the standard
+    /// conventions for this path, e.g. looking at the explicitly set compiler,
+    /// environment variables (a number of which are inspected here), and then
+    /// falling back to the default configuration.
+    ///
+    /// # Panics
+    ///
+    /// Panics if an error occurred while determining the architecture.
+    pub fn get_archiver(&self) -> Command {
+        match self.try_get_archiver() {
+            Ok(tool) => tool,
+            Err(e) => fail(&e.message),
+        }
+    }
+
+    /// Get the archiver that's in use for this configuration.
+    ///
+    /// This will return a result instead of panicing;
+    /// see [`get_archiver()`] for the complete description.
+    pub fn try_get_archiver(&self) -> Result<Command, Error> {
+        Ok(self.try_get_archiver_and_flags()?.0)
+    }
+
+    fn try_get_archiver_and_flags(&self) -> Result<(Command, String, bool), Error> {
+        let (mut cmd, name) = self.get_base_archiver()?;
+        let flags = self.envflags("ARFLAGS");
+        let mut any_flags = !flags.is_empty();
+        cmd.args(flags);
+        for flag in &self.ar_flags {
+            any_flags = true;
+            cmd.arg(flag);
+        }
+        Ok((cmd, name, any_flags))
+    }
+
+    fn get_base_archiver(&self) -> Result<(Command, String), Error> {
+        if let Some(ref a) = self.archiver {
+            return Ok((self.cmd(a), a.to_string_lossy().into_owned()));
+        }
+
+        self.get_base_archiver_variant("AR", "ar")
+    }
+
+    /// Get the ranlib that's in use for this configuration.
+    ///
+    /// You can use [`Command::get_program`] to get just the path to the command.
+    ///
+    /// This method will take into account all configuration such as debug
+    /// information, optimization level, include directories, defines, etc.
+    /// Additionally, the compiler binary in use follows the standard
+    /// conventions for this path, e.g. looking at the explicitly set compiler,
+    /// environment variables (a number of which are inspected here), and then
+    /// falling back to the default configuration.
+    ///
+    /// # Panics
+    ///
+    /// Panics if an error occurred while determining the architecture.
+    pub fn get_ranlib(&self) -> Command {
+        match self.try_get_ranlib() {
+            Ok(tool) => tool,
+            Err(e) => fail(&e.message),
+        }
+    }
+
+    /// Get the ranlib that's in use for this configuration.
+    ///
+    /// This will return a result instead of panicing;
+    /// see [`get_ranlib()`] for the complete description.
+    pub fn try_get_ranlib(&self) -> Result<Command, Error> {
+        let mut cmd = self.get_base_ranlib()?;
+        cmd.args(self.envflags("RANLIBFLAGS"));
+        Ok(cmd)
+    }
+
+    fn get_base_ranlib(&self) -> Result<Command, Error> {
+        if let Some(ref r) = self.ranlib {
+            return Ok(self.cmd(r));
+        }
+
+        Ok(self.get_base_archiver_variant("RANLIB", "ranlib")?.0)
+    }
+
+    fn get_base_archiver_variant(&self, env: &str, tool: &str) -> Result<(Command, String), Error> {
+        let target = self.get_target()?;
+        let mut name = String::new();
+        let tool_opt: Option<Command> = self
+            .env_tool(env)
+            .map(|(tool, _wrapper, args)| {
+                let mut cmd = self.cmd(tool);
+                cmd.args(args);
+                cmd
+            })
+            .or_else(|| {
+                if target.contains("emscripten") {
+                    // Windows use bat files so we have to be a bit more specific
+                    if cfg!(windows) {
+                        let mut cmd = self.cmd("cmd");
+                        name = format!("em{}.bat", tool);
+                        cmd.arg("/c").arg(&name);
+                        Some(cmd)
+                    } else {
+                        name = format!("em{}", tool);
+                        Some(self.cmd(&name))
+                    }
+                } else {
+                    None
+                }
+            });
+
+        let default = tool.to_string();
+        let tool = match tool_opt {
+            Some(t) => t,
+            None => {
+                if target.contains("android") {
+                    name = format!("{}-{}", target.replace("armv7", "arm"), tool);
+                    self.cmd(&name)
+                } else if target.contains("msvc") {
+                    // NOTE: There isn't really a ranlib on msvc, so arguably we should return
+                    // `None` somehow here. But in general, callers will already have to be aware
+                    // of not running ranlib on Windows anyway, so it feels okay to return lib.exe
+                    // here.
+
+                    let compiler = self.get_base_compiler()?;
+                    let mut lib = String::new();
+                    if compiler.family == (ToolFamily::Msvc { clang_cl: true }) {
+                        // See if there is 'llvm-lib' next to 'clang-cl'
+                        // Another possibility could be to see if there is 'clang'
+                        // next to 'clang-cl' and use 'search_programs()' to locate
+                        // 'llvm-lib'. This is because 'clang-cl' doesn't support
+                        // the -print-search-dirs option.
+                        if let Some(mut cmd) = which(&compiler.path) {
+                            cmd.pop();
+                            cmd.push("llvm-lib.exe");
+                            if let Some(llvm_lib) = which(&cmd) {
+                                lib = llvm_lib.to_str().unwrap().to_owned();
+                            }
+                        }
+                    }
+
+                    if lib.is_empty() {
+                        name = String::from("lib.exe");
+                        match windows_registry::find(&target, "lib.exe") {
+                            Some(t) => t,
+                            None => self.cmd("lib.exe"),
+                        }
+                    } else {
+                        name = lib;
+                        self.cmd(&name)
+                    }
+                } else if target.contains("illumos") {
+                    // The default 'ar' on illumos uses a non-standard flags,
+                    // but the OS comes bundled with a GNU-compatible variant.
+                    //
+                    // Use the GNU-variant to match other Unix systems.
+                    name = format!("g{}", tool);
+                    self.cmd(&name)
+                } else if self.get_host()? != target {
+                    match self.prefix_for_target(&target) {
+                        Some(p) => {
+                            // GCC uses $target-gcc-ar, whereas binutils uses $target-ar -- try both.
+                            // Prefer -ar if it exists, as builds of `-gcc-ar` have been observed to be
+                            // outright broken (such as when targetting freebsd with `--disable-lto`
+                            // toolchain where the archiver attempts to load the LTO plugin anyway but
+                            // fails to find one).
+                            //
+                            // The same applies to ranlib.
+                            let mut chosen = default;
+                            for &infix in &["", "-gcc"] {
+                                let target_p = format!("{}{}-{}", p, infix, tool);
+                                if Command::new(&target_p).output().is_ok() {
+                                    chosen = target_p;
+                                    break;
+                                }
+                            }
+                            name = chosen;
+                            self.cmd(&name)
+                        }
+                        None => {
+                            name = default;
+                            self.cmd(&name)
+                        }
+                    }
+                } else {
+                    name = default;
+                    self.cmd(&name)
+                }
+            }
+        };
+
+        Ok((tool, name))
+    }
+
+    fn prefix_for_target(&self, target: &str) -> Option<String> {
+        // Put aside RUSTC_LINKER's prefix to be used as last resort
+        let rustc_linker = self.getenv("RUSTC_LINKER").unwrap_or("".to_string());
+        // let linker_prefix = rustc_linker.strip_suffix("-gcc"); // >=1.45.0
+        let linker_prefix = if rustc_linker.len() > 4 {
+            let (prefix, suffix) = rustc_linker.split_at(rustc_linker.len() - 4);
+            if suffix == "-gcc" {
+                Some(prefix)
+            } else {
+                None
+            }
+        } else {
+            None
+        };
+        // CROSS_COMPILE is of the form: "arm-linux-gnueabi-"
+        let cc_env = self.getenv("CROSS_COMPILE");
+        let cross_compile = cc_env.as_ref().map(|s| s.trim_end_matches('-').to_owned());
+        cross_compile.or(match &target[..] {
+            // Note: there is no `aarch64-pc-windows-gnu` target, only `-gnullvm`
+            "aarch64-pc-windows-gnullvm" => Some("aarch64-w64-mingw32"),
+            "aarch64-uwp-windows-gnu" => Some("aarch64-w64-mingw32"),
+            "aarch64-unknown-linux-gnu" => Some("aarch64-linux-gnu"),
+            "aarch64-unknown-linux-musl" => Some("aarch64-linux-musl"),
+            "aarch64-unknown-netbsd" => Some("aarch64--netbsd"),
+            "arm-unknown-linux-gnueabi" => Some("arm-linux-gnueabi"),
+            "armv4t-unknown-linux-gnueabi" => Some("arm-linux-gnueabi"),
+            "armv5te-unknown-linux-gnueabi" => Some("arm-linux-gnueabi"),
+            "armv5te-unknown-linux-musleabi" => Some("arm-linux-gnueabi"),
+            "arm-frc-linux-gnueabi" => Some("arm-frc-linux-gnueabi"),
+            "arm-unknown-linux-gnueabihf" => Some("arm-linux-gnueabihf"),
+            "arm-unknown-linux-musleabi" => Some("arm-linux-musleabi"),
+            "arm-unknown-linux-musleabihf" => Some("arm-linux-musleabihf"),
+            "arm-unknown-netbsd-eabi" => Some("arm--netbsdelf-eabi"),
+            "armv6-unknown-netbsd-eabihf" => Some("armv6--netbsdelf-eabihf"),
+            "armv7-unknown-linux-gnueabi" => Some("arm-linux-gnueabi"),
+            "armv7-unknown-linux-gnueabihf" => Some("arm-linux-gnueabihf"),
+            "armv7-unknown-linux-musleabihf" => Some("arm-linux-musleabihf"),
+            "armv7neon-unknown-linux-gnueabihf" => Some("arm-linux-gnueabihf"),
+            "armv7neon-unknown-linux-musleabihf" => Some("arm-linux-musleabihf"),
+            "thumbv7-unknown-linux-gnueabihf" => Some("arm-linux-gnueabihf"),
+            "thumbv7-unknown-linux-musleabihf" => Some("arm-linux-musleabihf"),
+            "thumbv7neon-unknown-linux-gnueabihf" => Some("arm-linux-gnueabihf"),
+            "thumbv7neon-unknown-linux-musleabihf" => Some("arm-linux-musleabihf"),
+            "armv7-unknown-netbsd-eabihf" => Some("armv7--netbsdelf-eabihf"),
+            "hexagon-unknown-linux-musl" => Some("hexagon-linux-musl"),
+            "i586-unknown-linux-musl" => Some("musl"),
+            "i686-pc-windows-gnu" => Some("i686-w64-mingw32"),
+            "i686-uwp-windows-gnu" => Some("i686-w64-mingw32"),
+            "i686-unknown-linux-gnu" => self.find_working_gnu_prefix(&[
+                "i686-linux-gnu",
+                "x86_64-linux-gnu", // transparently support gcc-multilib
+            ]), // explicit None if not found, so caller knows to fall back
+            "i686-unknown-linux-musl" => Some("musl"),
+            "i686-unknown-netbsd" => Some("i486--netbsdelf"),
+            "mips-unknown-linux-gnu" => Some("mips-linux-gnu"),
+            "mips-unknown-linux-musl" => Some("mips-linux-musl"),
+            "mipsel-unknown-linux-gnu" => Some("mipsel-linux-gnu"),
+            "mipsel-unknown-linux-musl" => Some("mipsel-linux-musl"),
+            "mips64-unknown-linux-gnuabi64" => Some("mips64-linux-gnuabi64"),
+            "mips64el-unknown-linux-gnuabi64" => Some("mips64el-linux-gnuabi64"),
+            "mipsisa32r6-unknown-linux-gnu" => Some("mipsisa32r6-linux-gnu"),
+            "mipsisa32r6el-unknown-linux-gnu" => Some("mipsisa32r6el-linux-gnu"),
+            "mipsisa64r6-unknown-linux-gnuabi64" => Some("mipsisa64r6-linux-gnuabi64"),
+            "mipsisa64r6el-unknown-linux-gnuabi64" => Some("mipsisa64r6el-linux-gnuabi64"),
+            "powerpc-unknown-linux-gnu" => Some("powerpc-linux-gnu"),
+            "powerpc-unknown-linux-gnuspe" => Some("powerpc-linux-gnuspe"),
+            "powerpc-unknown-netbsd" => Some("powerpc--netbsd"),
+            "powerpc64-unknown-linux-gnu" => Some("powerpc-linux-gnu"),
+            "powerpc64le-unknown-linux-gnu" => Some("powerpc64le-linux-gnu"),
+            "riscv32i-unknown-none-elf" => self.find_working_gnu_prefix(&[
+                "riscv32-unknown-elf",
+                "riscv64-unknown-elf",
+                "riscv-none-embed",
+            ]),
+            "riscv32imac-unknown-none-elf" => self.find_working_gnu_prefix(&[
+                "riscv32-unknown-elf",
+                "riscv64-unknown-elf",
+                "riscv-none-embed",
+            ]),
+            "riscv32imac-unknown-xous-elf" => self.find_working_gnu_prefix(&[
+                "riscv32-unknown-elf",
+                "riscv64-unknown-elf",
+                "riscv-none-embed",
+            ]),
+            "riscv32imc-esp-espidf" => Some("riscv32-esp-elf"),
+            "riscv32imc-unknown-none-elf" => self.find_working_gnu_prefix(&[
+                "riscv32-unknown-elf",
+                "riscv64-unknown-elf",
+                "riscv-none-embed",
+            ]),
+            "riscv64gc-unknown-none-elf" => self.find_working_gnu_prefix(&[
+                "riscv64-unknown-elf",
+                "riscv32-unknown-elf",
+                "riscv-none-embed",
+            ]),
+            "riscv64imac-unknown-none-elf" => self.find_working_gnu_prefix(&[
+                "riscv64-unknown-elf",
+                "riscv32-unknown-elf",
+                "riscv-none-embed",
+            ]),
+            "riscv64gc-unknown-linux-gnu" => Some("riscv64-linux-gnu"),
+            "riscv32gc-unknown-linux-gnu" => Some("riscv32-linux-gnu"),
+            "riscv64gc-unknown-linux-musl" => Some("riscv64-linux-musl"),
+            "riscv32gc-unknown-linux-musl" => Some("riscv32-linux-musl"),
+            "s390x-unknown-linux-gnu" => Some("s390x-linux-gnu"),
+            "sparc-unknown-linux-gnu" => Some("sparc-linux-gnu"),
+            "sparc64-unknown-linux-gnu" => Some("sparc64-linux-gnu"),
+            "sparc64-unknown-netbsd" => Some("sparc64--netbsd"),
+            "sparcv9-sun-solaris" => Some("sparcv9-sun-solaris"),
+            "armv7a-none-eabi" => Some("arm-none-eabi"),
+            "armv7a-none-eabihf" => Some("arm-none-eabi"),
+            "armebv7r-none-eabi" => Some("arm-none-eabi"),
+            "armebv7r-none-eabihf" => Some("arm-none-eabi"),
+            "armv7r-none-eabi" => Some("arm-none-eabi"),
+            "armv7r-none-eabihf" => Some("arm-none-eabi"),
+            "thumbv6m-none-eabi" => Some("arm-none-eabi"),
+            "thumbv7em-none-eabi" => Some("arm-none-eabi"),
+            "thumbv7em-none-eabihf" => Some("arm-none-eabi"),
+            "thumbv7m-none-eabi" => Some("arm-none-eabi"),
+            "thumbv8m.base-none-eabi" => Some("arm-none-eabi"),
+            "thumbv8m.main-none-eabi" => Some("arm-none-eabi"),
+            "thumbv8m.main-none-eabihf" => Some("arm-none-eabi"),
+            "x86_64-pc-windows-gnu" => Some("x86_64-w64-mingw32"),
+            "x86_64-pc-windows-gnullvm" => Some("x86_64-w64-mingw32"),
+            "x86_64-uwp-windows-gnu" => Some("x86_64-w64-mingw32"),
+            "x86_64-rumprun-netbsd" => Some("x86_64-rumprun-netbsd"),
+            "x86_64-unknown-linux-gnu" => self.find_working_gnu_prefix(&[
+                "x86_64-linux-gnu", // rustfmt wrap
+            ]), // explicit None if not found, so caller knows to fall back
+            "x86_64-unknown-linux-musl" => Some("musl"),
+            "x86_64-unknown-netbsd" => Some("x86_64--netbsd"),
+            _ => linker_prefix,
+        }
+        .map(|x| x.to_owned()))
+    }
+
+    /// Some platforms have multiple, compatible, canonical prefixes. Look through
+    /// each possible prefix for a compiler that exists and return it. The prefixes
+    /// should be ordered from most-likely to least-likely.
+    fn find_working_gnu_prefix(&self, prefixes: &[&'static str]) -> Option<&'static str> {
+        let suffix = if self.cpp { "-g++" } else { "-gcc" };
+        let extension = std::env::consts::EXE_SUFFIX;
+
+        // Loop through PATH entries searching for each toolchain. This ensures that we
+        // are more likely to discover the toolchain early on, because chances are good
+        // that the desired toolchain is in one of the higher-priority paths.
+        env::var_os("PATH")
+            .as_ref()
+            .and_then(|path_entries| {
+                env::split_paths(path_entries).find_map(|path_entry| {
+                    for prefix in prefixes {
+                        let target_compiler = format!("{}{}{}", prefix, suffix, extension);
+                        if path_entry.join(&target_compiler).exists() {
+                            return Some(prefix);
+                        }
+                    }
+                    None
+                })
+            })
+            .map(|prefix| *prefix)
+            .or_else(||
+            // If no toolchain was found, provide the first toolchain that was passed in.
+            // This toolchain has been shown not to exist, however it will appear in the
+            // error that is shown to the user which should make it easier to search for
+            // where it should be obtained.
+            prefixes.first().map(|prefix| *prefix))
+    }
+
+    fn get_target(&self) -> Result<String, Error> {
+        match self.target.clone() {
+            Some(t) => Ok(t),
+            None => Ok(self.getenv_unwrap("TARGET")?),
+        }
+    }
+
+    fn get_host(&self) -> Result<String, Error> {
+        match self.host.clone() {
+            Some(h) => Ok(h),
+            None => Ok(self.getenv_unwrap("HOST")?),
+        }
+    }
+
+    fn get_opt_level(&self) -> Result<String, Error> {
+        match self.opt_level.as_ref().cloned() {
+            Some(ol) => Ok(ol),
+            None => Ok(self.getenv_unwrap("OPT_LEVEL")?),
+        }
+    }
+
+    fn get_debug(&self) -> bool {
+        self.debug.unwrap_or_else(|| match self.getenv("DEBUG") {
+            Some(s) => s != "false",
+            None => false,
+        })
+    }
+
+    fn get_dwarf_version(&self) -> Option<u32> {
+        // Tentatively matches the DWARF version defaults as of rustc 1.62.
+        let target = self.get_target().ok()?;
+        if target.contains("android")
+            || target.contains("apple")
+            || target.contains("dragonfly")
+            || target.contains("freebsd")
+            || target.contains("netbsd")
+            || target.contains("openbsd")
+            || target.contains("windows-gnu")
+        {
+            Some(2)
+        } else if target.contains("linux") {
+            Some(4)
+        } else {
+            None
+        }
+    }
+
+    fn get_force_frame_pointer(&self) -> bool {
+        self.force_frame_pointer.unwrap_or_else(|| self.get_debug())
+    }
+
+    fn get_out_dir(&self) -> Result<PathBuf, Error> {
+        match self.out_dir.clone() {
+            Some(p) => Ok(p),
+            None => Ok(env::var_os("OUT_DIR").map(PathBuf::from).ok_or_else(|| {
+                Error::new(
+                    ErrorKind::EnvVarNotFound,
+                    "Environment variable OUT_DIR not defined.",
+                )
+            })?),
+        }
+    }
+
+    fn getenv(&self, v: &str) -> Option<String> {
+        // Returns true for environment variables cargo sets for build scripts:
+        // https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-build-scripts
+        //
+        // This handles more of the vars than we actually use (it tries to check
+        // complete-ish set), just to avoid needing maintenance if/when new
+        // calls to `getenv`/`getenv_unwrap` are added.
+        fn provided_by_cargo(envvar: &str) -> bool {
+            match envvar {
+                v if v.starts_with("CARGO") || v.starts_with("RUSTC") => true,
+                "HOST" | "TARGET" | "RUSTDOC" | "OUT_DIR" | "OPT_LEVEL" | "DEBUG" | "PROFILE"
+                | "NUM_JOBS" | "RUSTFLAGS" => true,
+                _ => false,
+            }
+        }
+        let mut cache = self.env_cache.lock().unwrap();
+        if let Some(val) = cache.get(v) {
+            return val.clone();
+        }
+        if self.emit_rerun_if_env_changed && !provided_by_cargo(v) {
+            self.print(&format!("cargo:rerun-if-env-changed={}", v));
+        }
+        let r = env::var(v).ok();
+        self.print(&format!("{} = {:?}", v, r));
+        cache.insert(v.to_string(), r.clone());
+        r
+    }
+
+    fn getenv_unwrap(&self, v: &str) -> Result<String, Error> {
+        match self.getenv(v) {
+            Some(s) => Ok(s),
+            None => Err(Error::new(
+                ErrorKind::EnvVarNotFound,
+                &format!("Environment variable {} not defined.", v.to_string()),
+            )),
+        }
+    }
+
+    fn print(&self, s: &str) {
+        if self.cargo_metadata {
+            println!("{}", s);
+        }
+    }
+
+    fn fix_env_for_apple_os(&self, cmd: &mut Command) -> Result<(), Error> {
+        let target = self.get_target()?;
+        let host = self.get_host()?;
+        if host.contains("apple-darwin") && target.contains("apple-darwin") {
+            // If, for example, `cargo` runs during the build of an XCode project, then `SDKROOT` environment variable
+            // would represent the current target, and this is the problem for us, if we want to compile something
+            // for the host, when host != target.
+            // We can not just remove `SDKROOT`, because, again, for example, XCode add to PATH
+            // /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
+            // and `cc` from this path can not find system include files, like `pthread.h`, if `SDKROOT`
+            // is not set
+            if let Ok(sdkroot) = env::var("SDKROOT") {
+                if !sdkroot.contains("MacOSX") {
+                    let macos_sdk = self.apple_sdk_root("macosx")?;
+                    cmd.env("SDKROOT", macos_sdk);
+                }
+            }
+            // Additionally, `IPHONEOS_DEPLOYMENT_TARGET` must not be set when using the Xcode linker at
+            // "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld",
+            // although this is apparently ignored when using the linker at "/usr/bin/ld".
+            cmd.env_remove("IPHONEOS_DEPLOYMENT_TARGET");
+        }
+        Ok(())
+    }
+
+    fn apple_sdk_root(&self, sdk: &str) -> Result<OsString, Error> {
+        let mut cache = self
+            .apple_sdk_root_cache
+            .lock()
+            .expect("apple_sdk_root_cache lock failed");
+        if let Some(ret) = cache.get(sdk) {
+            return Ok(ret.clone());
+        }
+
+        let sdk_path = run_output(
+            self.cmd("xcrun")
+                .arg("--show-sdk-path")
+                .arg("--sdk")
+                .arg(sdk),
+            "xcrun",
+        )?;
+
+        let sdk_path = match String::from_utf8(sdk_path) {
+            Ok(p) => p,
+            Err(_) => {
+                return Err(Error::new(
+                    ErrorKind::IOError,
+                    "Unable to determine Apple SDK path.",
+                ));
+            }
+        };
+        let ret: OsString = sdk_path.trim().into();
+        cache.insert(sdk.into(), ret.clone());
+        Ok(ret)
+    }
+
+    fn cuda_file_count(&self) -> usize {
+        self.files
+            .iter()
+            .filter(|file| file.extension() == Some(OsStr::new("cu")))
+            .count()
+    }
+}
+
+impl Default for Build {
+    fn default() -> Build {
+        Build::new()
+    }
+}
+
+impl Tool {
+    fn new(path: PathBuf) -> Self {
+        Tool::with_features(path, None, false)
+    }
+
+    fn with_clang_driver(path: PathBuf, clang_driver: Option<&str>) -> Self {
+        Self::with_features(path, clang_driver, false)
+    }
+
+    #[cfg(windows)]
+    /// Explicitly set the `ToolFamily`, skipping name-based detection.
+    fn with_family(path: PathBuf, family: ToolFamily) -> Self {
+        Self {
+            path: path,
+            cc_wrapper_path: None,
+            cc_wrapper_args: Vec::new(),
+            args: Vec::new(),
+            env: Vec::new(),
+            family: family,
+            cuda: false,
+            removed_args: Vec::new(),
+        }
+    }
+
+    fn with_features(path: PathBuf, clang_driver: Option<&str>, cuda: bool) -> Self {
+        // Try to detect family of the tool from its name, falling back to Gnu.
+        let family = if let Some(fname) = path.file_name().and_then(|p| p.to_str()) {
+            if fname.contains("clang-cl") {
+                ToolFamily::Msvc { clang_cl: true }
+            } else if fname.ends_with("cl") || fname == "cl.exe" {
+                ToolFamily::Msvc { clang_cl: false }
+            } else if fname.contains("clang") {
+                match clang_driver {
+                    Some("cl") => ToolFamily::Msvc { clang_cl: true },
+                    _ => ToolFamily::Clang,
+                }
+            } else {
+                ToolFamily::Gnu
+            }
+        } else {
+            ToolFamily::Gnu
+        };
+
+        Tool {
+            path: path,
+            cc_wrapper_path: None,
+            cc_wrapper_args: Vec::new(),
+            args: Vec::new(),
+            env: Vec::new(),
+            family: family,
+            cuda: cuda,
+            removed_args: Vec::new(),
+        }
+    }
+
+    /// Add an argument to be stripped from the final command arguments.
+    fn remove_arg(&mut self, flag: OsString) {
+        self.removed_args.push(flag);
+    }
+
+    /// Add a flag, and optionally prepend the NVCC wrapper flag "-Xcompiler".
+    ///
+    /// Currently this is only used for compiling CUDA sources, since NVCC only
+    /// accepts a limited set of GNU-like flags, and the rest must be prefixed
+    /// with a "-Xcompiler" flag to get passed to the underlying C++ compiler.
+    fn push_cc_arg(&mut self, flag: OsString) {
+        if self.cuda {
+            self.args.push("-Xcompiler".into());
+        }
+        self.args.push(flag);
+    }
+
+    fn is_duplicate_opt_arg(&self, flag: &OsString) -> bool {
+        let flag = flag.to_str().unwrap();
+        let mut chars = flag.chars();
+
+        // Only duplicate check compiler flags
+        if self.is_like_msvc() {
+            if chars.next() != Some('/') {
+                return false;
+            }
+        } else if self.is_like_gnu() || self.is_like_clang() {
+            if chars.next() != Some('-') {
+                return false;
+            }
+        }
+
+        // Check for existing optimization flags (-O, /O)
+        if chars.next() == Some('O') {
+            return self
+                .args()
+                .iter()
+                .any(|ref a| a.to_str().unwrap_or("").chars().nth(1) == Some('O'));
+        }
+
+        // TODO Check for existing -m..., -m...=..., /arch:... flags
+        return false;
+    }
+
+    /// Don't push optimization arg if it conflicts with existing args
+    fn push_opt_unless_duplicate(&mut self, flag: OsString) {
+        if self.is_duplicate_opt_arg(&flag) {
+            println!("Info: Ignoring duplicate arg {:?}", &flag);
+        } else {
+            self.push_cc_arg(flag);
+        }
+    }
+
+    /// Converts this compiler into a `Command` that's ready to be run.
+    ///
+    /// This is useful for when the compiler needs to be executed and the
+    /// command returned will already have the initial arguments and environment
+    /// variables configured.
+    pub fn to_command(&self) -> Command {
+        let mut cmd = match self.cc_wrapper_path {
+            Some(ref cc_wrapper_path) => {
+                let mut cmd = Command::new(&cc_wrapper_path);
+                cmd.arg(&self.path);
+                cmd
+            }
+            None => Command::new(&self.path),
+        };
+        cmd.args(&self.cc_wrapper_args);
+
+        let value = self
+            .args
+            .iter()
+            .filter(|a| !self.removed_args.contains(a))
+            .collect::<Vec<_>>();
+        cmd.args(&value);
+
+        for &(ref k, ref v) in self.env.iter() {
+            cmd.env(k, v);
+        }
+        cmd
+    }
+
+    /// Returns the path for this compiler.
+    ///
+    /// Note that this may not be a path to a file on the filesystem, e.g. "cc",
+    /// but rather something which will be resolved when a process is spawned.
+    pub fn path(&self) -> &Path {
+        &self.path
+    }
+
+    /// Returns the default set of arguments to the compiler needed to produce
+    /// executables for the target this compiler generates.
+    pub fn args(&self) -> &[OsString] {
+        &self.args
+    }
+
+    /// Returns the set of environment variables needed for this compiler to
+    /// operate.
+    ///
+    /// This is typically only used for MSVC compilers currently.
+    pub fn env(&self) -> &[(OsString, OsString)] {
+        &self.env
+    }
+
+    /// Returns the compiler command in format of CC environment variable.
+    /// Or empty string if CC env was not present
+    ///
+    /// This is typically used by configure script
+    pub fn cc_env(&self) -> OsString {
+        match self.cc_wrapper_path {
+            Some(ref cc_wrapper_path) => {
+                let mut cc_env = cc_wrapper_path.as_os_str().to_owned();
+                cc_env.push(" ");
+                cc_env.push(self.path.to_path_buf().into_os_string());
+                for arg in self.cc_wrapper_args.iter() {
+                    cc_env.push(" ");
+                    cc_env.push(arg);
+                }
+                cc_env
+            }
+            None => OsString::from(""),
+        }
+    }
+
+    /// Returns the compiler flags in format of CFLAGS environment variable.
+    /// Important here - this will not be CFLAGS from env, its internal gcc's flags to use as CFLAGS
+    /// This is typically used by configure script
+    pub fn cflags_env(&self) -> OsString {
+        let mut flags = OsString::new();
+        for (i, arg) in self.args.iter().enumerate() {
+            if i > 0 {
+                flags.push(" ");
+            }
+            flags.push(arg);
+        }
+        flags
+    }
+
+    /// Whether the tool is GNU Compiler Collection-like.
+    pub fn is_like_gnu(&self) -> bool {
+        self.family == ToolFamily::Gnu
+    }
+
+    /// Whether the tool is Clang-like.
+    pub fn is_like_clang(&self) -> bool {
+        self.family == ToolFamily::Clang
+    }
+
+    /// Whether the tool is MSVC-like.
+    pub fn is_like_msvc(&self) -> bool {
+        match self.family {
+            ToolFamily::Msvc { .. } => true,
+            _ => false,
+        }
+    }
+}
+
+fn run(cmd: &mut Command, program: &str) -> Result<(), Error> {
+    let (mut child, print) = spawn(cmd, program)?;
+    let status = match child.wait() {
+        Ok(s) => s,
+        Err(_) => {
+            return Err(Error::new(
+                ErrorKind::ToolExecError,
+                &format!(
+                    "Failed to wait on spawned child process, command {:?} with args {:?}.",
+                    cmd, program
+                ),
+            ));
+        }
+    };
+    print.join().unwrap();
+    println!("{}", status);
+
+    if status.success() {
+        Ok(())
+    } else {
+        Err(Error::new(
+            ErrorKind::ToolExecError,
+            &format!(
+                "Command {:?} with args {:?} did not execute successfully (status code {}).",
+                cmd, program, status
+            ),
+        ))
+    }
+}
+
+fn run_output(cmd: &mut Command, program: &str) -> Result<Vec<u8>, Error> {
+    cmd.stdout(Stdio::piped());
+    let (mut child, print) = spawn(cmd, program)?;
+    let mut stdout = vec![];
+    child
+        .stdout
+        .take()
+        .unwrap()
+        .read_to_end(&mut stdout)
+        .unwrap();
+    let status = match child.wait() {
+        Ok(s) => s,
+        Err(_) => {
+            return Err(Error::new(
+                ErrorKind::ToolExecError,
+                &format!(
+                    "Failed to wait on spawned child process, command {:?} with args {:?}.",
+                    cmd, program
+                ),
+            ));
+        }
+    };
+    print.join().unwrap();
+    println!("{}", status);
+
+    if status.success() {
+        Ok(stdout)
+    } else {
+        Err(Error::new(
+            ErrorKind::ToolExecError,
+            &format!(
+                "Command {:?} with args {:?} did not execute successfully (status code {}).",
+                cmd, program, status
+            ),
+        ))
+    }
+}
+
+fn spawn(cmd: &mut Command, program: &str) -> Result<(Child, JoinHandle<()>), Error> {
+    println!("running: {:?}", cmd);
+
+    // Capture the standard error coming from these programs, and write it out
+    // with cargo:warning= prefixes. Note that this is a bit wonky to avoid
+    // requiring the output to be UTF-8, we instead just ship bytes from one
+    // location to another.
+    match cmd.stderr(Stdio::piped()).spawn() {
+        Ok(mut child) => {
+            let stderr = BufReader::new(child.stderr.take().unwrap());
+            let print = thread::spawn(move || {
+                for line in stderr.split(b'\n').filter_map(|l| l.ok()) {
+                    print!("cargo:warning=");
+                    std::io::stdout().write_all(&line).unwrap();
+                    println!("");
+                }
+            });
+            Ok((child, print))
+        }
+        Err(ref e) if e.kind() == io::ErrorKind::NotFound => {
+            let extra = if cfg!(windows) {
+                " (see https://github.com/rust-lang/cc-rs#compile-time-requirements \
+                 for help)"
+            } else {
+                ""
+            };
+            Err(Error::new(
+                ErrorKind::ToolNotFound,
+                &format!("Failed to find tool. Is `{}` installed?{}", program, extra),
+            ))
+        }
+        Err(ref e) => Err(Error::new(
+            ErrorKind::ToolExecError,
+            &format!(
+                "Command {:?} with args {:?} failed to start: {:?}",
+                cmd, program, e
+            ),
+        )),
+    }
+}
+
+fn fail(s: &str) -> ! {
+    eprintln!("\n\nerror occurred: {}\n\n", s);
+    std::process::exit(1);
+}
+
+fn command_add_output_file(
+    cmd: &mut Command,
+    dst: &Path,
+    cuda: bool,
+    msvc: bool,
+    clang: bool,
+    is_asm: bool,
+    is_arm: bool,
+) {
+    if msvc && !clang && !cuda && !(is_asm && is_arm) {
+        let mut s = OsString::from("-Fo");
+        s.push(&dst);
+        cmd.arg(s);
+    } else {
+        cmd.arg("-o").arg(&dst);
+    }
+}
+
+// Use by default minimum available API level
+// See note about naming here
+// https://android.googlesource.com/platform/ndk/+/refs/heads/ndk-release-r21/docs/BuildSystemMaintainers.md#Clang
+static NEW_STANDALONE_ANDROID_COMPILERS: [&str; 4] = [
+    "aarch64-linux-android21-clang",
+    "armv7a-linux-androideabi16-clang",
+    "i686-linux-android16-clang",
+    "x86_64-linux-android21-clang",
+];
+
+// New "standalone" C/C++ cross-compiler executables from recent Android NDK
+// are just shell scripts that call main clang binary (from Android NDK) with
+// proper `--target` argument.
+//
+// For example, armv7a-linux-androideabi16-clang passes
+// `--target=armv7a-linux-androideabi16` to clang.
+// So to construct proper command line check if
+// `--target` argument would be passed or not to clang
+fn android_clang_compiler_uses_target_arg_internally(clang_path: &Path) -> bool {
+    if let Some(filename) = clang_path.file_name() {
+        if let Some(filename_str) = filename.to_str() {
+            filename_str.contains("android")
+        } else {
+            false
+        }
+    } else {
+        false
+    }
+}
+
+#[test]
+fn test_android_clang_compiler_uses_target_arg_internally() {
+    for version in 16..21 {
+        assert!(android_clang_compiler_uses_target_arg_internally(
+            &PathBuf::from(format!("armv7a-linux-androideabi{}-clang", version))
+        ));
+        assert!(android_clang_compiler_uses_target_arg_internally(
+            &PathBuf::from(format!("armv7a-linux-androideabi{}-clang++", version))
+        ));
+    }
+    assert!(!android_clang_compiler_uses_target_arg_internally(
+        &PathBuf::from("clang")
+    ));
+    assert!(!android_clang_compiler_uses_target_arg_internally(
+        &PathBuf::from("clang++")
+    ));
+}
+
+fn autodetect_android_compiler(target: &str, host: &str, gnu: &str, clang: &str) -> String {
+    let new_clang_key = match target {
+        "aarch64-linux-android" => Some("aarch64"),
+        "armv7-linux-androideabi" => Some("armv7a"),
+        "i686-linux-android" => Some("i686"),
+        "x86_64-linux-android" => Some("x86_64"),
+        _ => None,
+    };
+
+    let new_clang = new_clang_key
+        .map(|key| {
+            NEW_STANDALONE_ANDROID_COMPILERS
+                .iter()
+                .find(|x| x.starts_with(key))
+        })
+        .unwrap_or(None);
+
+    if let Some(new_clang) = new_clang {
+        if Command::new(new_clang).output().is_ok() {
+            return (*new_clang).into();
+        }
+    }
+
+    let target = target
+        .replace("armv7neon", "arm")
+        .replace("armv7", "arm")
+        .replace("thumbv7neon", "arm")
+        .replace("thumbv7", "arm");
+    let gnu_compiler = format!("{}-{}", target, gnu);
+    let clang_compiler = format!("{}-{}", target, clang);
+
+    // On Windows, the Android clang compiler is provided as a `.cmd` file instead
+    // of a `.exe` file. `std::process::Command` won't run `.cmd` files unless the
+    // `.cmd` is explicitly appended to the command name, so we do that here.
+    let clang_compiler_cmd = format!("{}-{}.cmd", target, clang);
+
+    // Check if gnu compiler is present
+    // if not, use clang
+    if Command::new(&gnu_compiler).output().is_ok() {
+        gnu_compiler
+    } else if host.contains("windows") && Command::new(&clang_compiler_cmd).output().is_ok() {
+        clang_compiler_cmd
+    } else {
+        clang_compiler
+    }
+}
+
+// Rust and clang/cc don't agree on how to name the target.
+fn map_darwin_target_from_rust_to_compiler_architecture(target: &str) -> Option<&'static str> {
+    if target.contains("x86_64") {
+        Some("x86_64")
+    } else if target.contains("arm64e") {
+        Some("arm64e")
+    } else if target.contains("aarch64") {
+        Some("arm64")
+    } else if target.contains("i686") {
+        Some("i386")
+    } else if target.contains("powerpc") {
+        Some("ppc")
+    } else if target.contains("powerpc64") {
+        Some("ppc64")
+    } else {
+        None
+    }
+}
+
+fn which(tool: &Path) -> Option<PathBuf> {
+    fn check_exe(exe: &mut PathBuf) -> bool {
+        let exe_ext = std::env::consts::EXE_EXTENSION;
+        exe.exists() || (!exe_ext.is_empty() && exe.set_extension(exe_ext) && exe.exists())
+    }
+
+    // If |tool| is not just one "word," assume it's an actual path...
+    if tool.components().count() > 1 {
+        let mut exe = PathBuf::from(tool);
+        return if check_exe(&mut exe) { Some(exe) } else { None };
+    }
+
+    // Loop through PATH entries searching for the |tool|.
+    let path_entries = env::var_os("PATH")?;
+    env::split_paths(&path_entries).find_map(|path_entry| {
+        let mut exe = path_entry.join(tool);
+        return if check_exe(&mut exe) { Some(exe) } else { None };
+    })
+}
+
+#[derive(Clone, Copy, PartialEq)]
+enum AsmFileExt {
+    /// `.asm` files. On MSVC targets, we assume these should be passed to MASM
+    /// (`ml{,64}.exe`).
+    DotAsm,
+    /// `.s` or `.S` files, which do not have the special handling on MSVC targets.
+    DotS,
+}
+
+impl AsmFileExt {
+    fn from_path(file: &Path) -> Option<Self> {
+        if let Some(ext) = file.extension() {
+            if let Some(ext) = ext.to_str() {
+                let ext = ext.to_lowercase();
+                match &*ext {
+                    "asm" => return Some(AsmFileExt::DotAsm),
+                    "s" => return Some(AsmFileExt::DotS),
+                    _ => return None,
+                }
+            }
+        }
+        None
+    }
+}
diff --git a/src/registry.rs b/src/registry.rs
new file mode 100644
index 0000000..cae3221
--- /dev/null
+++ b/src/registry.rs
@@ -0,0 +1,231 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::ffi::{OsStr, OsString};
+use std::io;
+use std::ops::RangeFrom;
+use std::os::raw;
+use std::os::windows::prelude::*;
+
+/// Must never be `HKEY_PERFORMANCE_DATA`.
+pub(crate) struct RegistryKey(Repr);
+
+type HKEY = *mut u8;
+type DWORD = u32;
+type LPDWORD = *mut DWORD;
+type LPCWSTR = *const u16;
+type LPWSTR = *mut u16;
+type LONG = raw::c_long;
+type PHKEY = *mut HKEY;
+type PFILETIME = *mut u8;
+type LPBYTE = *mut u8;
+type REGSAM = u32;
+
+const ERROR_SUCCESS: DWORD = 0;
+const ERROR_NO_MORE_ITEMS: DWORD = 259;
+// Sign-extend into 64 bits if needed.
+const HKEY_LOCAL_MACHINE: HKEY = 0x80000002u32 as i32 as isize as HKEY;
+const REG_SZ: DWORD = 1;
+const KEY_READ: DWORD = 0x20019;
+const KEY_WOW64_32KEY: DWORD = 0x200;
+
+#[link(name = "advapi32")]
+extern "system" {
+    fn RegOpenKeyExW(
+        key: HKEY,
+        lpSubKey: LPCWSTR,
+        ulOptions: DWORD,
+        samDesired: REGSAM,
+        phkResult: PHKEY,
+    ) -> LONG;
+    fn RegEnumKeyExW(
+        key: HKEY,
+        dwIndex: DWORD,
+        lpName: LPWSTR,
+        lpcName: LPDWORD,
+        lpReserved: LPDWORD,
+        lpClass: LPWSTR,
+        lpcClass: LPDWORD,
+        lpftLastWriteTime: PFILETIME,
+    ) -> LONG;
+    fn RegQueryValueExW(
+        hKey: HKEY,
+        lpValueName: LPCWSTR,
+        lpReserved: LPDWORD,
+        lpType: LPDWORD,
+        lpData: LPBYTE,
+        lpcbData: LPDWORD,
+    ) -> LONG;
+    fn RegCloseKey(hKey: HKEY) -> LONG;
+}
+
+struct OwnedKey(HKEY);
+
+/// Note: must not encode `HKEY_PERFORMANCE_DATA` or one of its subkeys.
+enum Repr {
+    /// `HKEY_LOCAL_MACHINE`.
+    LocalMachine,
+    /// A subkey of `HKEY_LOCAL_MACHINE`.
+    Owned(OwnedKey),
+}
+
+pub struct Iter<'a> {
+    idx: RangeFrom<DWORD>,
+    key: &'a RegistryKey,
+}
+
+unsafe impl Sync for Repr {}
+unsafe impl Send for Repr {}
+
+pub(crate) const LOCAL_MACHINE: RegistryKey = RegistryKey(Repr::LocalMachine);
+
+impl RegistryKey {
+    fn raw(&self) -> HKEY {
+        match self.0 {
+            Repr::LocalMachine => HKEY_LOCAL_MACHINE,
+            Repr::Owned(ref val) => val.0,
+        }
+    }
+
+    /// Open a sub-key of `self`.
+    pub fn open(&self, key: &OsStr) -> io::Result<RegistryKey> {
+        let key = key.encode_wide().chain(Some(0)).collect::<Vec<_>>();
+        let mut ret = 0 as *mut _;
+        let err = unsafe {
+            RegOpenKeyExW(
+                self.raw(),
+                key.as_ptr(),
+                0,
+                KEY_READ | KEY_WOW64_32KEY,
+                &mut ret,
+            )
+        };
+        if err == ERROR_SUCCESS as LONG {
+            Ok(RegistryKey(Repr::Owned(OwnedKey(ret))))
+        } else {
+            Err(io::Error::from_raw_os_error(err as i32))
+        }
+    }
+
+    pub fn iter(&self) -> Iter {
+        Iter {
+            idx: 0..,
+            key: self,
+        }
+    }
+
+    pub fn query_str(&self, name: &str) -> io::Result<OsString> {
+        let name: &OsStr = name.as_ref();
+        let name = name.encode_wide().chain(Some(0)).collect::<Vec<_>>();
+        let mut len = 0;
+        let mut kind = 0;
+        unsafe {
+            let err = RegQueryValueExW(
+                self.raw(),
+                name.as_ptr(),
+                0 as *mut _,
+                &mut kind,
+                0 as *mut _,
+                &mut len,
+            );
+            if err != ERROR_SUCCESS as LONG {
+                return Err(io::Error::from_raw_os_error(err as i32));
+            }
+            if kind != REG_SZ {
+                return Err(io::Error::new(
+                    io::ErrorKind::Other,
+                    "registry key wasn't a string",
+                ));
+            }
+
+            // The length here is the length in bytes, but we're using wide
+            // characters so we need to be sure to halve it for the length
+            // passed in.
+            assert!(len % 2 == 0, "impossible wide string size: {} bytes", len);
+            let vlen = len as usize / 2;
+            // Defensively initialized, see comment about
+            // `HKEY_PERFORMANCE_DATA` below.
+            let mut v = vec![0u16; vlen];
+            let err = RegQueryValueExW(
+                self.raw(),
+                name.as_ptr(),
+                0 as *mut _,
+                0 as *mut _,
+                v.as_mut_ptr() as *mut _,
+                &mut len,
+            );
+            // We don't check for `ERROR_MORE_DATA` (which would if the value
+            // grew between the first and second call to `RegQueryValueExW`),
+            // both because it's extremely unlikely, and this is a bit more
+            // defensive more defensive against weird types of registry keys.
+            if err != ERROR_SUCCESS as LONG {
+                return Err(io::Error::from_raw_os_error(err as i32));
+            }
+            // The length is allowed to change, but should still be even, as
+            // well as smaller.
+            assert!(len % 2 == 0, "impossible wide string size: {} bytes", len);
+            // If the length grew but returned a success code, it *probably*
+            // indicates we're `HKEY_PERFORMANCE_DATA` or a subkey(?). We
+            // consider this UB, since those keys write "undefined" or
+            // "unpredictable" values to len, and need to use a completely
+            // different loop structure. This should be impossible (and enforce
+            // it in the API to the best of our ability), but to mitigate the
+            // damage we do some smoke-checks on the len, and ensure `v` has
+            // been fully initialized (rather than trusting the result of
+            // `RegQueryValueExW`).
+            let actual_len = len as usize / 2;
+            assert!(actual_len <= v.len());
+            v.truncate(actual_len);
+            // Some registry keys may have a terminating nul character, but
+            // we're not interested in that, so chop it off if it's there.
+            if !v.is_empty() && v[v.len() - 1] == 0 {
+                v.pop();
+            }
+            return Ok(OsString::from_wide(&v));
+        }
+    }
+}
+
+impl Drop for OwnedKey {
+    fn drop(&mut self) {
+        unsafe {
+            RegCloseKey(self.0);
+        }
+    }
+}
+
+impl<'a> Iterator for Iter<'a> {
+    type Item = io::Result<OsString>;
+
+    fn next(&mut self) -> Option<io::Result<OsString>> {
+        self.idx.next().and_then(|i| unsafe {
+            let mut v = Vec::with_capacity(256);
+            let mut len = v.capacity() as DWORD;
+            let ret = RegEnumKeyExW(
+                self.key.raw(),
+                i,
+                v.as_mut_ptr(),
+                &mut len,
+                0 as *mut _,
+                0 as *mut _,
+                0 as *mut _,
+                0 as *mut _,
+            );
+            if ret == ERROR_NO_MORE_ITEMS as LONG {
+                None
+            } else if ret != ERROR_SUCCESS as LONG {
+                Some(Err(io::Error::from_raw_os_error(ret as i32)))
+            } else {
+                v.set_len(len as usize);
+                Some(Ok(OsString::from_wide(&v)))
+            }
+        })
+    }
+}
diff --git a/src/setup_config.rs b/src/setup_config.rs
new file mode 100644
index 0000000..030051c
--- /dev/null
+++ b/src/setup_config.rs
@@ -0,0 +1,283 @@
+// Copyright © 2017 winapi-rs developers
+// Licensed under the Apache License, Version 2.0
+// <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
+// All files in the project carrying such notice may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(bad_style)]
+#![allow(unused)]
+
+use crate::winapi::Interface;
+use crate::winapi::BSTR;
+use crate::winapi::LPCOLESTR;
+use crate::winapi::LPSAFEARRAY;
+use crate::winapi::S_FALSE;
+use crate::winapi::{CoCreateInstance, CLSCTX_ALL};
+use crate::winapi::{IUnknown, IUnknownVtbl};
+use crate::winapi::{HRESULT, LCID, LPCWSTR, PULONGLONG};
+use crate::winapi::{LPFILETIME, ULONG};
+use std::ffi::OsString;
+use std::ptr::null_mut;
+
+use crate::com::{BStr, ComPtr};
+
+// Bindings to the Setup.Configuration stuff
+pub type InstanceState = u32;
+
+pub const eNone: InstanceState = 0;
+pub const eLocal: InstanceState = 1;
+pub const eRegistered: InstanceState = 2;
+pub const eNoRebootRequired: InstanceState = 4;
+pub const eComplete: InstanceState = -1i32 as u32;
+
+RIDL! {#[uuid(0xb41463c3, 0x8866, 0x43b5, 0xbc, 0x33, 0x2b, 0x06, 0x76, 0xf7, 0xf4, 0x2e)]
+interface ISetupInstance(ISetupInstanceVtbl): IUnknown(IUnknownVtbl) {
+    fn GetInstanceId(
+        pbstrInstanceId: *mut BSTR,
+    ) -> HRESULT,
+    fn GetInstallDate(
+        pInstallDate: LPFILETIME,
+    ) -> HRESULT,
+    fn GetInstallationName(
+        pbstrInstallationName: *mut BSTR,
+    ) -> HRESULT,
+    fn GetInstallationPath(
+        pbstrInstallationPath: *mut BSTR,
+    ) -> HRESULT,
+    fn GetInstallationVersion(
+        pbstrInstallationVersion: *mut BSTR,
+    ) -> HRESULT,
+    fn GetDisplayName(
+        lcid: LCID,
+        pbstrDisplayName: *mut BSTR,
+    ) -> HRESULT,
+    fn GetDescription(
+        lcid: LCID,
+        pbstrDescription: *mut BSTR,
+    ) -> HRESULT,
+    fn ResolvePath(
+        pwszRelativePath: LPCOLESTR,
+        pbstrAbsolutePath: *mut BSTR,
+    ) -> HRESULT,
+}}
+
+RIDL! {#[uuid(0x89143c9a, 0x05af, 0x49b0, 0xb7, 0x17, 0x72, 0xe2, 0x18, 0xa2, 0x18, 0x5c)]
+interface ISetupInstance2(ISetupInstance2Vtbl): ISetupInstance(ISetupInstanceVtbl) {
+    fn GetState(
+        pState: *mut InstanceState,
+    ) -> HRESULT,
+    fn GetPackages(
+        ppsaPackages: *mut LPSAFEARRAY,
+    ) -> HRESULT,
+    fn GetProduct(
+        ppPackage: *mut *mut ISetupPackageReference,
+    ) -> HRESULT,
+    fn GetProductPath(
+        pbstrProductPath: *mut BSTR,
+    ) -> HRESULT,
+}}
+
+RIDL! {#[uuid(0x6380bcff, 0x41d3, 0x4b2e, 0x8b, 0x2e, 0xbf, 0x8a, 0x68, 0x10, 0xc8, 0x48)]
+interface IEnumSetupInstances(IEnumSetupInstancesVtbl): IUnknown(IUnknownVtbl) {
+    fn Next(
+        celt: ULONG,
+        rgelt: *mut *mut ISetupInstance,
+        pceltFetched: *mut ULONG,
+    ) -> HRESULT,
+    fn Skip(
+        celt: ULONG,
+    ) -> HRESULT,
+    fn Reset() -> HRESULT,
+    fn Clone(
+        ppenum: *mut *mut IEnumSetupInstances,
+    ) -> HRESULT,
+}}
+
+RIDL! {#[uuid(0x42843719, 0xdb4c, 0x46c2, 0x8e, 0x7c, 0x64, 0xf1, 0x81, 0x6e, 0xfd, 0x5b)]
+interface ISetupConfiguration(ISetupConfigurationVtbl): IUnknown(IUnknownVtbl) {
+    fn EnumInstances(
+        ppEnumInstances: *mut *mut IEnumSetupInstances,
+    ) -> HRESULT,
+    fn GetInstanceForCurrentProcess(
+        ppInstance: *mut *mut ISetupInstance,
+    ) -> HRESULT,
+    fn GetInstanceForPath(
+        wzPath: LPCWSTR,
+        ppInstance: *mut *mut ISetupInstance,
+    ) -> HRESULT,
+}}
+
+RIDL! {#[uuid(0x26aab78c, 0x4a60, 0x49d6, 0xaf, 0x3b, 0x3c, 0x35, 0xbc, 0x93, 0x36, 0x5d)]
+interface ISetupConfiguration2(ISetupConfiguration2Vtbl):
+    ISetupConfiguration(ISetupConfigurationVtbl) {
+    fn EnumAllInstances(
+        ppEnumInstances: *mut *mut IEnumSetupInstances,
+    ) -> HRESULT,
+}}
+
+RIDL! {#[uuid(0xda8d8a16, 0xb2b6, 0x4487, 0xa2, 0xf1, 0x59, 0x4c, 0xcc, 0xcd, 0x6b, 0xf5)]
+interface ISetupPackageReference(ISetupPackageReferenceVtbl): IUnknown(IUnknownVtbl) {
+    fn GetId(
+        pbstrId: *mut BSTR,
+    ) -> HRESULT,
+    fn GetVersion(
+        pbstrVersion: *mut BSTR,
+    ) -> HRESULT,
+    fn GetChip(
+        pbstrChip: *mut BSTR,
+    ) -> HRESULT,
+    fn GetLanguage(
+        pbstrLanguage: *mut BSTR,
+    ) -> HRESULT,
+    fn GetBranch(
+        pbstrBranch: *mut BSTR,
+    ) -> HRESULT,
+    fn GetType(
+        pbstrType: *mut BSTR,
+    ) -> HRESULT,
+    fn GetUniqueId(
+        pbstrUniqueId: *mut BSTR,
+    ) -> HRESULT,
+}}
+
+RIDL! {#[uuid(0x42b21b78, 0x6192, 0x463e, 0x87, 0xbf, 0xd5, 0x77, 0x83, 0x8f, 0x1d, 0x5c)]
+interface ISetupHelper(ISetupHelperVtbl): IUnknown(IUnknownVtbl) {
+    fn ParseVersion(
+        pwszVersion: LPCOLESTR,
+        pullVersion: PULONGLONG,
+    ) -> HRESULT,
+    fn ParseVersionRange(
+        pwszVersionRange: LPCOLESTR,
+        pullMinVersion: PULONGLONG,
+        pullMaxVersion: PULONGLONG,
+    ) -> HRESULT,
+}}
+
+DEFINE_GUID! {CLSID_SetupConfiguration,
+0x177f0c4a, 0x1cd3, 0x4de7, 0xa3, 0x2c, 0x71, 0xdb, 0xbb, 0x9f, 0xa3, 0x6d}
+
+// Safe wrapper around the COM interfaces
+pub struct SetupConfiguration(ComPtr<ISetupConfiguration>);
+
+impl SetupConfiguration {
+    pub fn new() -> Result<SetupConfiguration, i32> {
+        let mut obj = null_mut();
+        let err = unsafe {
+            CoCreateInstance(
+                &CLSID_SetupConfiguration,
+                null_mut(),
+                CLSCTX_ALL,
+                &ISetupConfiguration::uuidof(),
+                &mut obj,
+            )
+        };
+        if err < 0 {
+            return Err(err);
+        }
+        let obj = unsafe { ComPtr::from_raw(obj as *mut ISetupConfiguration) };
+        Ok(SetupConfiguration(obj))
+    }
+    pub fn get_instance_for_current_process(&self) -> Result<SetupInstance, i32> {
+        let mut obj = null_mut();
+        let err = unsafe { self.0.GetInstanceForCurrentProcess(&mut obj) };
+        if err < 0 {
+            return Err(err);
+        }
+        Ok(unsafe { SetupInstance::from_raw(obj) })
+    }
+    pub fn enum_instances(&self) -> Result<EnumSetupInstances, i32> {
+        let mut obj = null_mut();
+        let err = unsafe { self.0.EnumInstances(&mut obj) };
+        if err < 0 {
+            return Err(err);
+        }
+        Ok(unsafe { EnumSetupInstances::from_raw(obj) })
+    }
+    pub fn enum_all_instances(&self) -> Result<EnumSetupInstances, i32> {
+        let mut obj = null_mut();
+        let this = self.0.cast::<ISetupConfiguration2>()?;
+        let err = unsafe { this.EnumAllInstances(&mut obj) };
+        if err < 0 {
+            return Err(err);
+        }
+        Ok(unsafe { EnumSetupInstances::from_raw(obj) })
+    }
+}
+
+pub struct SetupInstance(ComPtr<ISetupInstance>);
+
+impl SetupInstance {
+    pub unsafe fn from_raw(obj: *mut ISetupInstance) -> SetupInstance {
+        SetupInstance(ComPtr::from_raw(obj))
+    }
+    pub fn instance_id(&self) -> Result<OsString, i32> {
+        let mut s = null_mut();
+        let err = unsafe { self.0.GetInstanceId(&mut s) };
+        let bstr = unsafe { BStr::from_raw(s) };
+        if err < 0 {
+            return Err(err);
+        }
+        Ok(bstr.to_osstring())
+    }
+    pub fn installation_name(&self) -> Result<OsString, i32> {
+        let mut s = null_mut();
+        let err = unsafe { self.0.GetInstallationName(&mut s) };
+        let bstr = unsafe { BStr::from_raw(s) };
+        if err < 0 {
+            return Err(err);
+        }
+        Ok(bstr.to_osstring())
+    }
+    pub fn installation_path(&self) -> Result<OsString, i32> {
+        let mut s = null_mut();
+        let err = unsafe { self.0.GetInstallationPath(&mut s) };
+        let bstr = unsafe { BStr::from_raw(s) };
+        if err < 0 {
+            return Err(err);
+        }
+        Ok(bstr.to_osstring())
+    }
+    pub fn installation_version(&self) -> Result<OsString, i32> {
+        let mut s = null_mut();
+        let err = unsafe { self.0.GetInstallationVersion(&mut s) };
+        let bstr = unsafe { BStr::from_raw(s) };
+        if err < 0 {
+            return Err(err);
+        }
+        Ok(bstr.to_osstring())
+    }
+    pub fn product_path(&self) -> Result<OsString, i32> {
+        let mut s = null_mut();
+        let this = self.0.cast::<ISetupInstance2>()?;
+        let err = unsafe { this.GetProductPath(&mut s) };
+        let bstr = unsafe { BStr::from_raw(s) };
+        if err < 0 {
+            return Err(err);
+        }
+        Ok(bstr.to_osstring())
+    }
+}
+
+pub struct EnumSetupInstances(ComPtr<IEnumSetupInstances>);
+
+impl EnumSetupInstances {
+    pub unsafe fn from_raw(obj: *mut IEnumSetupInstances) -> EnumSetupInstances {
+        EnumSetupInstances(ComPtr::from_raw(obj))
+    }
+}
+
+impl Iterator for EnumSetupInstances {
+    type Item = Result<SetupInstance, i32>;
+    fn next(&mut self) -> Option<Result<SetupInstance, i32>> {
+        let mut obj = null_mut();
+        let err = unsafe { self.0.Next(1, &mut obj, null_mut()) };
+        if err < 0 {
+            return Some(Err(err));
+        }
+        if err == S_FALSE {
+            return None;
+        }
+        Some(Ok(unsafe { SetupInstance::from_raw(obj) }))
+    }
+}
diff --git a/src/vs_instances.rs b/src/vs_instances.rs
new file mode 100644
index 0000000..31d3dd1
--- /dev/null
+++ b/src/vs_instances.rs
@@ -0,0 +1,199 @@
+use std::borrow::Cow;
+use std::collections::HashMap;
+use std::convert::TryFrom;
+use std::io::BufRead;
+use std::path::PathBuf;
+
+use crate::setup_config::{EnumSetupInstances, SetupInstance};
+
+pub enum VsInstance {
+    Com(SetupInstance),
+    Vswhere(VswhereInstance),
+}
+
+impl VsInstance {
+    pub fn installation_name(&self) -> Option<Cow<str>> {
+        match self {
+            VsInstance::Com(s) => s
+                .installation_name()
+                .ok()
+                .and_then(|s| s.into_string().ok())
+                .map(Cow::from),
+            VsInstance::Vswhere(v) => v.map.get("installationName").map(Cow::from),
+        }
+    }
+
+    pub fn installation_path(&self) -> Option<PathBuf> {
+        match self {
+            VsInstance::Com(s) => s.installation_path().ok().map(PathBuf::from),
+            VsInstance::Vswhere(v) => v.map.get("installationPath").map(PathBuf::from),
+        }
+    }
+
+    pub fn installation_version(&self) -> Option<Cow<str>> {
+        match self {
+            VsInstance::Com(s) => s
+                .installation_version()
+                .ok()
+                .and_then(|s| s.into_string().ok())
+                .map(Cow::from),
+            VsInstance::Vswhere(v) => v.map.get("installationVersion").map(Cow::from),
+        }
+    }
+}
+
+pub enum VsInstances {
+    ComBased(EnumSetupInstances),
+    VswhereBased(VswhereInstance),
+}
+
+impl IntoIterator for VsInstances {
+    type Item = VsInstance;
+    #[allow(bare_trait_objects)]
+    type IntoIter = Box<Iterator<Item = Self::Item>>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        match self {
+            VsInstances::ComBased(e) => {
+                Box::new(e.into_iter().filter_map(Result::ok).map(VsInstance::Com))
+            }
+            VsInstances::VswhereBased(v) => Box::new(std::iter::once(VsInstance::Vswhere(v))),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct VswhereInstance {
+    map: HashMap<String, String>,
+}
+
+impl TryFrom<&Vec<u8>> for VswhereInstance {
+    type Error = &'static str;
+
+    fn try_from(output: &Vec<u8>) -> Result<Self, Self::Error> {
+        let map: HashMap<_, _> = output
+            .lines()
+            .filter_map(Result::ok)
+            .filter_map(|s| {
+                let mut splitn = s.splitn(2, ": ");
+                Some((splitn.next()?.to_owned(), splitn.next()?.to_owned()))
+            })
+            .collect();
+
+        if !map.contains_key("installationName")
+            || !map.contains_key("installationPath")
+            || !map.contains_key("installationVersion")
+        {
+            return Err("required properties not found");
+        }
+
+        Ok(Self { map })
+    }
+}
+
+#[cfg(test)]
+mod tests_ {
+    use std::borrow::Cow;
+    use std::convert::TryFrom;
+    use std::path::PathBuf;
+
+    #[test]
+    fn it_parses_vswhere_output_correctly() {
+        let output = br"instanceId: 58104422
+installDate: 21/02/2021 21:50:33
+installationName: VisualStudio/16.9.2+31112.23
+installationPath: C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools
+installationVersion: 16.9.31112.23
+productId: Microsoft.VisualStudio.Product.BuildTools
+productPath: C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\Common7\Tools\LaunchDevCmd.bat
+state: 4294967295
+isComplete: 1
+isLaunchable: 1
+isPrerelease: 0
+isRebootRequired: 0
+displayName: Visual Studio Build Tools 2019
+description: The Visual Studio Build Tools allows you to build native and managed MSBuild-based applications without requiring the Visual Studio IDE. There are options to install the Visual C++ compilers and libraries, MFC, ATL, and C++/CLI support.
+channelId: VisualStudio.16.Release
+channelUri: https://aka.ms/vs/16/release/channel
+enginePath: C:\Program Files (x86)\Microsoft Visual Studio\Installer\resources\app\ServiceHub\Services\Microsoft.VisualStudio.Setup.Service
+releaseNotes: https://docs.microsoft.com/en-us/visualstudio/releases/2019/release-notes-v16.9#16.9.2
+thirdPartyNotices: https://go.microsoft.com/fwlink/?LinkId=660909
+updateDate: 2021-03-17T21:16:46.5963702Z
+catalog_buildBranch: d16.9
+catalog_buildVersion: 16.9.31112.23
+catalog_id: VisualStudio/16.9.2+31112.23
+catalog_localBuild: build-lab
+catalog_manifestName: VisualStudio
+catalog_manifestType: installer
+catalog_productDisplayVersion: 16.9.2
+catalog_productLine: Dev16
+catalog_productLineVersion: 2019
+catalog_productMilestone: RTW
+catalog_productMilestoneIsPreRelease: False
+catalog_productName: Visual Studio
+catalog_productPatchVersion: 2
+catalog_productPreReleaseMilestoneSuffix: 1.0
+catalog_productSemanticVersion: 16.9.2+31112.23
+catalog_requiredEngineVersion: 2.9.3365.38425
+properties_campaignId: 156063665.1613940062
+properties_channelManifestId: VisualStudio.16.Release/16.9.2+31112.23
+properties_nickname: 
+properties_setupEngineFilePath: C:\Program Files (x86)\Microsoft Visual Studio\Installer\vs_installershell.exe
+"
+        .to_vec();
+
+        let vswhere_instance = super::VswhereInstance::try_from(&output);
+        assert!(vswhere_instance.is_ok());
+
+        let vs_instance = super::VsInstance::Vswhere(vswhere_instance.unwrap());
+        assert_eq!(
+            vs_instance.installation_name(),
+            Some(Cow::from("VisualStudio/16.9.2+31112.23"))
+        );
+        assert_eq!(
+            vs_instance.installation_path(),
+            Some(PathBuf::from(
+                r"C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools"
+            ))
+        );
+        assert_eq!(
+            vs_instance.installation_version(),
+            Some(Cow::from("16.9.31112.23"))
+        );
+    }
+
+    #[test]
+    fn it_returns_an_error_for_empty_output() {
+        let output = b"".to_vec();
+
+        let vswhere_instance = super::VswhereInstance::try_from(&output);
+
+        assert!(vswhere_instance.is_err());
+    }
+
+    #[test]
+    fn it_returns_an_error_for_output_consisting_of_empty_lines() {
+        let output = br"
+
+"
+        .to_vec();
+
+        let vswhere_instance = super::VswhereInstance::try_from(&output);
+
+        assert!(vswhere_instance.is_err());
+    }
+
+    #[test]
+    fn it_returns_an_error_for_output_without_required_properties() {
+        let output = br"instanceId: 58104422
+installDate: 21/02/2021 21:50:33
+productId: Microsoft.VisualStudio.Product.BuildTools
+productPath: C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\Common7\Tools\LaunchDevCmd.bat
+"
+        .to_vec();
+
+        let vswhere_instance = super::VswhereInstance::try_from(&output);
+
+        assert!(vswhere_instance.is_err());
+    }
+}
diff --git a/src/winapi.rs b/src/winapi.rs
new file mode 100644
index 0000000..8e04ce9
--- /dev/null
+++ b/src/winapi.rs
@@ -0,0 +1,218 @@
+// Copyright © 2015-2017 winapi-rs developers
+// Licensed under the Apache License, Version 2.0
+// <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
+// All files in the project carrying such notice may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(bad_style)]
+
+use std::os::raw;
+
+pub type wchar_t = u16;
+
+pub type UINT = raw::c_uint;
+pub type LPUNKNOWN = *mut IUnknown;
+pub type REFIID = *const IID;
+pub type IID = GUID;
+pub type REFCLSID = *const IID;
+pub type PVOID = *mut raw::c_void;
+pub type USHORT = raw::c_ushort;
+pub type ULONG = raw::c_ulong;
+pub type LONG = raw::c_long;
+pub type DWORD = u32;
+pub type LPVOID = *mut raw::c_void;
+pub type HRESULT = raw::c_long;
+pub type LPFILETIME = *mut FILETIME;
+pub type BSTR = *mut OLECHAR;
+pub type OLECHAR = WCHAR;
+pub type WCHAR = wchar_t;
+pub type LPCOLESTR = *const OLECHAR;
+pub type LCID = DWORD;
+pub type LPCWSTR = *const WCHAR;
+pub type PULONGLONG = *mut ULONGLONG;
+pub type ULONGLONG = u64;
+
+pub const S_OK: HRESULT = 0;
+pub const S_FALSE: HRESULT = 1;
+pub const COINIT_MULTITHREADED: u32 = 0x0;
+
+pub type CLSCTX = u32;
+
+pub const CLSCTX_INPROC_SERVER: CLSCTX = 0x1;
+pub const CLSCTX_INPROC_HANDLER: CLSCTX = 0x2;
+pub const CLSCTX_LOCAL_SERVER: CLSCTX = 0x4;
+pub const CLSCTX_REMOTE_SERVER: CLSCTX = 0x10;
+
+pub const CLSCTX_ALL: CLSCTX =
+    CLSCTX_INPROC_SERVER | CLSCTX_INPROC_HANDLER | CLSCTX_LOCAL_SERVER | CLSCTX_REMOTE_SERVER;
+
+#[repr(C)]
+#[derive(Copy, Clone)]
+pub struct GUID {
+    pub Data1: raw::c_ulong,
+    pub Data2: raw::c_ushort,
+    pub Data3: raw::c_ushort,
+    pub Data4: [raw::c_uchar; 8],
+}
+
+#[repr(C)]
+#[derive(Copy, Clone)]
+pub struct FILETIME {
+    pub dwLowDateTime: DWORD,
+    pub dwHighDateTime: DWORD,
+}
+
+pub trait Interface {
+    fn uuidof() -> GUID;
+}
+
+#[link(name = "ole32")]
+#[link(name = "oleaut32")]
+extern "C" {}
+
+extern "system" {
+    pub fn CoInitializeEx(pvReserved: LPVOID, dwCoInit: DWORD) -> HRESULT;
+    pub fn CoCreateInstance(
+        rclsid: REFCLSID,
+        pUnkOuter: LPUNKNOWN,
+        dwClsContext: DWORD,
+        riid: REFIID,
+        ppv: *mut LPVOID,
+    ) -> HRESULT;
+    pub fn SysFreeString(bstrString: BSTR);
+    pub fn SysStringLen(pbstr: BSTR) -> UINT;
+}
+
+#[repr(C)]
+#[derive(Copy, Clone)]
+pub struct SAFEARRAYBOUND {
+    pub cElements: ULONG,
+    pub lLbound: LONG,
+}
+
+#[repr(C)]
+#[derive(Copy, Clone)]
+pub struct SAFEARRAY {
+    pub cDims: USHORT,
+    pub fFeatures: USHORT,
+    pub cbElements: ULONG,
+    pub cLocks: ULONG,
+    pub pvData: PVOID,
+    pub rgsabound: [SAFEARRAYBOUND; 1],
+}
+
+pub type LPSAFEARRAY = *mut SAFEARRAY;
+
+macro_rules! DEFINE_GUID {
+    (
+        $name:ident, $l:expr, $w1:expr, $w2:expr,
+        $b1:expr, $b2:expr, $b3:expr, $b4:expr, $b5:expr, $b6:expr, $b7:expr, $b8:expr
+    ) => {
+        pub const $name: $crate::winapi::GUID = $crate::winapi::GUID {
+            Data1: $l,
+            Data2: $w1,
+            Data3: $w2,
+            Data4: [$b1, $b2, $b3, $b4, $b5, $b6, $b7, $b8],
+        };
+    };
+}
+
+macro_rules! RIDL {
+    (#[uuid($($uuid:expr),+)]
+    interface $interface:ident ($vtbl:ident) {$(
+        fn $method:ident($($p:ident : $t:ty,)*) -> $rtr:ty,
+    )+}) => (
+        #[repr(C)]
+        pub struct $vtbl {
+            $(pub $method: unsafe extern "system" fn(
+                This: *mut $interface,
+                $($p: $t),*
+            ) -> $rtr,)+
+        }
+        #[repr(C)]
+        pub struct $interface {
+            pub lpVtbl: *const $vtbl,
+        }
+        RIDL!{@impl $interface {$(fn $method($($p: $t,)*) -> $rtr,)+}}
+        RIDL!{@uuid $interface $($uuid),+}
+    );
+    (#[uuid($($uuid:expr),+)]
+    interface $interface:ident ($vtbl:ident) : $pinterface:ident ($pvtbl:ident) {
+    }) => (
+        #[repr(C)]
+        pub struct $vtbl {
+            pub parent: $pvtbl,
+        }
+        #[repr(C)]
+        pub struct $interface {
+            pub lpVtbl: *const $vtbl,
+        }
+        RIDL!{@deref $interface $pinterface}
+        RIDL!{@uuid $interface $($uuid),+}
+    );
+    (#[uuid($($uuid:expr),+)]
+    interface $interface:ident ($vtbl:ident) : $pinterface:ident ($pvtbl:ident) {$(
+        fn $method:ident($($p:ident : $t:ty,)*) -> $rtr:ty,
+    )+}) => (
+        #[repr(C)]
+        pub struct $vtbl {
+            pub parent: $pvtbl,
+            $(pub $method: unsafe extern "system" fn(
+                This: *mut $interface,
+                $($p: $t,)*
+            ) -> $rtr,)+
+        }
+        #[repr(C)]
+        pub struct $interface {
+            pub lpVtbl: *const $vtbl,
+        }
+        RIDL!{@impl $interface {$(fn $method($($p: $t,)*) -> $rtr,)+}}
+        RIDL!{@deref $interface $pinterface}
+        RIDL!{@uuid $interface $($uuid),+}
+    );
+    (@deref $interface:ident $pinterface:ident) => (
+        impl ::std::ops::Deref for $interface {
+            type Target = $pinterface;
+            #[inline]
+            fn deref(&self) -> &$pinterface {
+                unsafe { &*(self as *const $interface as *const $pinterface) }
+            }
+        }
+    );
+    (@impl $interface:ident {$(
+        fn $method:ident($($p:ident : $t:ty,)*) -> $rtr:ty,
+    )+}) => (
+        impl $interface {
+            $(#[inline] pub unsafe fn $method(&self, $($p: $t,)*) -> $rtr {
+                ((*self.lpVtbl).$method)(self as *const _ as *mut _, $($p,)*)
+            })+
+        }
+    );
+    (@uuid $interface:ident
+        $l:expr, $w1:expr, $w2:expr,
+        $b1:expr, $b2:expr, $b3:expr, $b4:expr, $b5:expr, $b6:expr, $b7:expr, $b8:expr
+    ) => (
+        impl $crate::winapi::Interface for $interface {
+            #[inline]
+            fn uuidof() -> $crate::winapi::GUID {
+                $crate::winapi::GUID {
+                    Data1: $l,
+                    Data2: $w1,
+                    Data3: $w2,
+                    Data4: [$b1, $b2, $b3, $b4, $b5, $b6, $b7, $b8],
+                }
+            }
+        }
+    );
+}
+
+RIDL! {#[uuid(0x00000000, 0x0000, 0x0000, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x46)]
+interface IUnknown(IUnknownVtbl) {
+    fn QueryInterface(
+        riid: REFIID,
+        ppvObject: *mut *mut raw::c_void,
+    ) -> HRESULT,
+    fn AddRef() -> ULONG,
+    fn Release() -> ULONG,
+}}
diff --git a/src/windows_registry.rs b/src/windows_registry.rs
new file mode 100644
index 0000000..b05498c
--- /dev/null
+++ b/src/windows_registry.rs
@@ -0,0 +1,902 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! A helper module to probe the Windows Registry when looking for
+//! windows-specific tools.
+
+use std::process::Command;
+
+use crate::Tool;
+#[cfg(windows)]
+use crate::ToolFamily;
+
+#[cfg(windows)]
+const MSVC_FAMILY: ToolFamily = ToolFamily::Msvc { clang_cl: false };
+
+/// Attempts to find a tool within an MSVC installation using the Windows
+/// registry as a point to search from.
+///
+/// The `target` argument is the target that the tool should work for (e.g.
+/// compile or link for) and the `tool` argument is the tool to find (e.g.
+/// `cl.exe` or `link.exe`).
+///
+/// This function will return `None` if the tool could not be found, or it will
+/// return `Some(cmd)` which represents a command that's ready to execute the
+/// tool with the appropriate environment variables set.
+///
+/// Note that this function always returns `None` for non-MSVC targets.
+pub fn find(target: &str, tool: &str) -> Option<Command> {
+    find_tool(target, tool).map(|c| c.to_command())
+}
+
+/// Similar to the `find` function above, this function will attempt the same
+/// operation (finding a MSVC tool in a local install) but instead returns a
+/// `Tool` which may be introspected.
+#[cfg(not(windows))]
+pub fn find_tool(_target: &str, _tool: &str) -> Option<Tool> {
+    None
+}
+
+/// Documented above.
+#[cfg(windows)]
+pub fn find_tool(target: &str, tool: &str) -> Option<Tool> {
+    // This logic is all tailored for MSVC, if we're not that then bail out
+    // early.
+    if !target.contains("msvc") {
+        return None;
+    }
+
+    // Looks like msbuild isn't located in the same location as other tools like
+    // cl.exe and lib.exe. To handle this we probe for it manually with
+    // dedicated registry keys.
+    if tool.contains("msbuild") {
+        return impl_::find_msbuild(target);
+    }
+
+    if tool.contains("devenv") {
+        return impl_::find_devenv(target);
+    }
+
+    // Ok, if we're here, now comes the fun part of the probing. Default shells
+    // or shells like MSYS aren't really configured to execute `cl.exe` and the
+    // various compiler tools shipped as part of Visual Studio. Here we try to
+    // first find the relevant tool, then we also have to be sure to fill in
+    // environment variables like `LIB`, `INCLUDE`, and `PATH` to ensure that
+    // the tool is actually usable.
+
+    return impl_::find_msvc_environment(tool, target)
+        .or_else(|| impl_::find_msvc_15plus(tool, target))
+        .or_else(|| impl_::find_msvc_14(tool, target))
+        .or_else(|| impl_::find_msvc_12(tool, target))
+        .or_else(|| impl_::find_msvc_11(tool, target));
+}
+
+/// A version of Visual Studio
+#[derive(Debug, PartialEq, Eq, Copy, Clone)]
+pub enum VsVers {
+    /// Visual Studio 12 (2013)
+    Vs12,
+    /// Visual Studio 14 (2015)
+    Vs14,
+    /// Visual Studio 15 (2017)
+    Vs15,
+    /// Visual Studio 16 (2019)
+    Vs16,
+    /// Visual Studio 17 (2022)
+    Vs17,
+
+    /// Hidden variant that should not be matched on. Callers that want to
+    /// handle an enumeration of `VsVers` instances should always have a default
+    /// case meaning that it's a VS version they don't understand.
+    #[doc(hidden)]
+    #[allow(bad_style)]
+    __Nonexhaustive_do_not_match_this_or_your_code_will_break,
+}
+
+/// Find the most recent installed version of Visual Studio
+///
+/// This is used by the cmake crate to figure out the correct
+/// generator.
+#[cfg(not(windows))]
+pub fn find_vs_version() -> Result<VsVers, String> {
+    Err(format!("not windows"))
+}
+
+/// Documented above
+#[cfg(windows)]
+pub fn find_vs_version() -> Result<VsVers, String> {
+    use std::env;
+
+    match env::var("VisualStudioVersion") {
+        Ok(version) => match &version[..] {
+            "17.0" => Ok(VsVers::Vs17),
+            "16.0" => Ok(VsVers::Vs16),
+            "15.0" => Ok(VsVers::Vs15),
+            "14.0" => Ok(VsVers::Vs14),
+            "12.0" => Ok(VsVers::Vs12),
+            vers => Err(format!(
+                "\n\n\
+                 unsupported or unknown VisualStudio version: {}\n\
+                 if another version is installed consider running \
+                 the appropriate vcvars script before building this \
+                 crate\n\
+                 ",
+                vers
+            )),
+        },
+        _ => {
+            // Check for the presence of a specific registry key
+            // that indicates visual studio is installed.
+            if impl_::has_msbuild_version("17.0") {
+                Ok(VsVers::Vs17)
+            } else if impl_::has_msbuild_version("16.0") {
+                Ok(VsVers::Vs16)
+            } else if impl_::has_msbuild_version("15.0") {
+                Ok(VsVers::Vs15)
+            } else if impl_::has_msbuild_version("14.0") {
+                Ok(VsVers::Vs14)
+            } else if impl_::has_msbuild_version("12.0") {
+                Ok(VsVers::Vs12)
+            } else {
+                Err(format!(
+                    "\n\n\
+                     couldn't determine visual studio generator\n\
+                     if VisualStudio is installed, however, consider \
+                     running the appropriate vcvars script before building \
+                     this crate\n\
+                     "
+                ))
+            }
+        }
+    }
+}
+
+#[cfg(windows)]
+mod impl_ {
+    use crate::com;
+    use crate::registry::{RegistryKey, LOCAL_MACHINE};
+    use crate::setup_config::SetupConfiguration;
+    use crate::vs_instances::{VsInstances, VswhereInstance};
+    use std::convert::TryFrom;
+    use std::env;
+    use std::ffi::OsString;
+    use std::fs::File;
+    use std::io::Read;
+    use std::iter;
+    use std::mem;
+    use std::path::{Path, PathBuf};
+    use std::process::Command;
+    use std::str::FromStr;
+
+    use super::MSVC_FAMILY;
+    use crate::Tool;
+
+    struct MsvcTool {
+        tool: PathBuf,
+        libs: Vec<PathBuf>,
+        path: Vec<PathBuf>,
+        include: Vec<PathBuf>,
+    }
+
+    impl MsvcTool {
+        fn new(tool: PathBuf) -> MsvcTool {
+            MsvcTool {
+                tool: tool,
+                libs: Vec::new(),
+                path: Vec::new(),
+                include: Vec::new(),
+            }
+        }
+
+        fn into_tool(self) -> Tool {
+            let MsvcTool {
+                tool,
+                libs,
+                path,
+                include,
+            } = self;
+            let mut tool = Tool::with_family(tool.into(), MSVC_FAMILY);
+            add_env(&mut tool, "LIB", libs);
+            add_env(&mut tool, "PATH", path);
+            add_env(&mut tool, "INCLUDE", include);
+            tool
+        }
+    }
+
+    /// Checks to see if the `VSCMD_ARG_TGT_ARCH` environment variable matches the
+    /// given target's arch. Returns `None` if the variable does not exist.
+    #[cfg(windows)]
+    fn is_vscmd_target(target: &str) -> Option<bool> {
+        let vscmd_arch = env::var("VSCMD_ARG_TGT_ARCH").ok()?;
+        // Convert the Rust target arch to its VS arch equivalent.
+        let arch = match target.split("-").next() {
+            Some("x86_64") => "x64",
+            Some("aarch64") => "arm64",
+            Some("i686") | Some("i586") => "x86",
+            Some("thumbv7a") => "arm",
+            // An unrecognized arch.
+            _ => return Some(false),
+        };
+        Some(vscmd_arch == arch)
+    }
+
+    /// Attempt to find the tool using environment variables set by vcvars.
+    pub fn find_msvc_environment(tool: &str, target: &str) -> Option<Tool> {
+        // Early return if the environment doesn't contain a VC install.
+        if env::var_os("VCINSTALLDIR").is_none() {
+            return None;
+        }
+        let vs_install_dir = env::var_os("VSINSTALLDIR")?.into();
+
+        // If the vscmd target differs from the requested target then
+        // attempt to get the tool using the VS install directory.
+        if is_vscmd_target(target) == Some(false) {
+            // We will only get here with versions 15+.
+            tool_from_vs15plus_instance(tool, target, &vs_install_dir)
+        } else {
+            // Fallback to simply using the current environment.
+            env::var_os("PATH")
+                .and_then(|path| {
+                    env::split_paths(&path)
+                        .map(|p| p.join(tool))
+                        .find(|p| p.exists())
+                })
+                .map(|path| Tool::with_family(path.into(), MSVC_FAMILY))
+        }
+    }
+
+    fn find_msbuild_vs17(target: &str) -> Option<Tool> {
+        find_tool_in_vs16plus_path(r"MSBuild\Current\Bin\MSBuild.exe", target, "17")
+    }
+
+    #[allow(bare_trait_objects)]
+    fn vs16plus_instances(target: &str, version: &'static str) -> Box<Iterator<Item = PathBuf>> {
+        let instances = if let Some(instances) = vs15plus_instances(target) {
+            instances
+        } else {
+            return Box::new(iter::empty());
+        };
+        Box::new(instances.into_iter().filter_map(move |instance| {
+            let installation_name = instance.installation_name()?;
+            if installation_name.starts_with(&format!("VisualStudio/{}.", version)) {
+                Some(instance.installation_path()?)
+            } else if installation_name.starts_with(&format!("VisualStudioPreview/{}.", version)) {
+                Some(instance.installation_path()?)
+            } else {
+                None
+            }
+        }))
+    }
+
+    fn find_tool_in_vs16plus_path(tool: &str, target: &str, version: &'static str) -> Option<Tool> {
+        vs16plus_instances(target, version)
+            .filter_map(|path| {
+                let path = path.join(tool);
+                if !path.is_file() {
+                    return None;
+                }
+                let mut tool = Tool::with_family(path, MSVC_FAMILY);
+                if target.contains("x86_64") {
+                    tool.env.push(("Platform".into(), "X64".into()));
+                }
+                if target.contains("aarch64") {
+                    tool.env.push(("Platform".into(), "ARM64".into()));
+                }
+                Some(tool)
+            })
+            .next()
+    }
+
+    fn find_msbuild_vs16(target: &str) -> Option<Tool> {
+        find_tool_in_vs16plus_path(r"MSBuild\Current\Bin\MSBuild.exe", target, "16")
+    }
+
+    // In MSVC 15 (2017) MS once again changed the scheme for locating
+    // the tooling.  Now we must go through some COM interfaces, which
+    // is super fun for Rust.
+    //
+    // Note that much of this logic can be found [online] wrt paths, COM, etc.
+    //
+    // [online]: https://blogs.msdn.microsoft.com/vcblog/2017/03/06/finding-the-visual-c-compiler-tools-in-visual-studio-2017/
+    //
+    // Returns MSVC 15+ instances (15, 16 right now), the order should be consider undefined.
+    //
+    // However, on ARM64 this method doesn't work because VS Installer fails to register COM component on ARM64.
+    // Hence, as the last resort we try to use vswhere.exe to list available instances.
+    fn vs15plus_instances(target: &str) -> Option<VsInstances> {
+        vs15plus_instances_using_com().or_else(|| vs15plus_instances_using_vswhere(target))
+    }
+
+    fn vs15plus_instances_using_com() -> Option<VsInstances> {
+        com::initialize().ok()?;
+
+        let config = SetupConfiguration::new().ok()?;
+        let enum_setup_instances = config.enum_all_instances().ok()?;
+
+        Some(VsInstances::ComBased(enum_setup_instances))
+    }
+
+    fn vs15plus_instances_using_vswhere(target: &str) -> Option<VsInstances> {
+        let program_files_path: PathBuf = env::var("ProgramFiles(x86)")
+            .or_else(|_| env::var("ProgramFiles"))
+            .ok()?
+            .into();
+
+        let vswhere_path =
+            program_files_path.join(r"Microsoft Visual Studio\Installer\vswhere.exe");
+
+        if !vswhere_path.exists() {
+            return None;
+        }
+
+        let arch = target.split('-').next().unwrap();
+        let tools_arch = match arch {
+            "i586" | "i686" | "x86_64" => Some("x86.x64"),
+            "arm" | "thumbv7a" => Some("ARM"),
+            "aarch64" => Some("ARM64"),
+            _ => None,
+        };
+
+        let vswhere_output = Command::new(vswhere_path)
+            .args(&[
+                "-latest",
+                "-products",
+                "*",
+                "-requires",
+                &format!("Microsoft.VisualStudio.Component.VC.Tools.{}", tools_arch?),
+                "-format",
+                "text",
+                "-nologo",
+            ])
+            .stderr(std::process::Stdio::inherit())
+            .output()
+            .ok()?;
+
+        let vs_instances =
+            VsInstances::VswhereBased(VswhereInstance::try_from(&vswhere_output.stdout).ok()?);
+
+        Some(vs_instances)
+    }
+
+    // Inspired from official microsoft/vswhere ParseVersionString
+    // i.e. at most four u16 numbers separated by '.'
+    fn parse_version(version: &str) -> Option<Vec<u16>> {
+        version
+            .split('.')
+            .map(|chunk| u16::from_str(chunk).ok())
+            .collect()
+    }
+
+    pub fn find_msvc_15plus(tool: &str, target: &str) -> Option<Tool> {
+        let iter = vs15plus_instances(target)?;
+        iter.into_iter()
+            .filter_map(|instance| {
+                let version = parse_version(&instance.installation_version()?)?;
+                let instance_path = instance.installation_path()?;
+                let tool = tool_from_vs15plus_instance(tool, target, &instance_path)?;
+                Some((version, tool))
+            })
+            .max_by(|(a_version, _), (b_version, _)| a_version.cmp(b_version))
+            .map(|(_version, tool)| tool)
+    }
+
+    // While the paths to Visual Studio 2017's devenv and MSBuild could
+    // potentially be retrieved from the registry, finding them via
+    // SetupConfiguration has shown to be [more reliable], and is preferred
+    // according to Microsoft. To help head off potential regressions though,
+    // we keep the registry method as a fallback option.
+    //
+    // [more reliable]: https://github.com/rust-lang/cc-rs/pull/331
+    fn find_tool_in_vs15_path(tool: &str, target: &str) -> Option<Tool> {
+        let mut path = match vs15plus_instances(target) {
+            Some(instances) => instances
+                .into_iter()
+                .filter_map(|instance| instance.installation_path())
+                .map(|path| path.join(tool))
+                .find(|ref path| path.is_file()),
+            None => None,
+        };
+
+        if path.is_none() {
+            let key = r"SOFTWARE\WOW6432Node\Microsoft\VisualStudio\SxS\VS7";
+            path = LOCAL_MACHINE
+                .open(key.as_ref())
+                .ok()
+                .and_then(|key| key.query_str("15.0").ok())
+                .map(|path| PathBuf::from(path).join(tool))
+                .and_then(|path| if path.is_file() { Some(path) } else { None });
+        }
+
+        path.map(|path| {
+            let mut tool = Tool::with_family(path, MSVC_FAMILY);
+            if target.contains("x86_64") {
+                tool.env.push(("Platform".into(), "X64".into()));
+            }
+            if target.contains("aarch64") {
+                tool.env.push(("Platform".into(), "ARM64".into()));
+            }
+            tool
+        })
+    }
+
+    fn tool_from_vs15plus_instance(
+        tool: &str,
+        target: &str,
+        instance_path: &PathBuf,
+    ) -> Option<Tool> {
+        let (root_path, bin_path, host_dylib_path, lib_path, include_path) =
+            vs15plus_vc_paths(target, instance_path)?;
+        let tool_path = bin_path.join(tool);
+        if !tool_path.exists() {
+            return None;
+        };
+
+        let mut tool = MsvcTool::new(tool_path);
+        tool.path.push(bin_path.clone());
+        tool.path.push(host_dylib_path);
+        tool.libs.push(lib_path);
+        tool.include.push(include_path);
+
+        if let Some((atl_lib_path, atl_include_path)) = atl_paths(target, &root_path) {
+            tool.libs.push(atl_lib_path);
+            tool.include.push(atl_include_path);
+        }
+
+        add_sdks(&mut tool, target)?;
+
+        Some(tool.into_tool())
+    }
+
+    fn vs15plus_vc_paths(
+        target: &str,
+        instance_path: &PathBuf,
+    ) -> Option<(PathBuf, PathBuf, PathBuf, PathBuf, PathBuf)> {
+        let version_path =
+            instance_path.join(r"VC\Auxiliary\Build\Microsoft.VCToolsVersion.default.txt");
+        let mut version_file = File::open(version_path).ok()?;
+        let mut version = String::new();
+        version_file.read_to_string(&mut version).ok()?;
+        let version = version.trim();
+        let host = match host_arch() {
+            X86 => "X86",
+            X86_64 => "X64",
+            // There is no natively hosted compiler on ARM64.
+            // Instead, use the x86 toolchain under emulation (there is no x64 emulation).
+            AARCH64 => "X86",
+            _ => return None,
+        };
+        let target = lib_subdir(target)?;
+        // The directory layout here is MSVC/bin/Host$host/$target/
+        let path = instance_path.join(r"VC\Tools\MSVC").join(version);
+        // This is the path to the toolchain for a particular target, running
+        // on a given host
+        let bin_path = path
+            .join("bin")
+            .join(&format!("Host{}", host))
+            .join(&target);
+        // But! we also need PATH to contain the target directory for the host
+        // architecture, because it contains dlls like mspdb140.dll compiled for
+        // the host architecture.
+        let host_dylib_path = path
+            .join("bin")
+            .join(&format!("Host{}", host))
+            .join(&host.to_lowercase());
+        let lib_path = path.join("lib").join(&target);
+        let include_path = path.join("include");
+        Some((path, bin_path, host_dylib_path, lib_path, include_path))
+    }
+
+    fn atl_paths(target: &str, path: &Path) -> Option<(PathBuf, PathBuf)> {
+        let atl_path = path.join("atlmfc");
+        let sub = lib_subdir(target)?;
+        if atl_path.exists() {
+            Some((atl_path.join("lib").join(sub), atl_path.join("include")))
+        } else {
+            None
+        }
+    }
+
+    // For MSVC 14 we need to find the Universal CRT as well as either
+    // the Windows 10 SDK or Windows 8.1 SDK.
+    pub fn find_msvc_14(tool: &str, target: &str) -> Option<Tool> {
+        let vcdir = get_vc_dir("14.0")?;
+        let mut tool = get_tool(tool, &vcdir, target)?;
+        add_sdks(&mut tool, target)?;
+        Some(tool.into_tool())
+    }
+
+    fn add_sdks(tool: &mut MsvcTool, target: &str) -> Option<()> {
+        let sub = lib_subdir(target)?;
+        let (ucrt, ucrt_version) = get_ucrt_dir()?;
+
+        let host = match host_arch() {
+            X86 => "x86",
+            X86_64 => "x64",
+            AARCH64 => "arm64",
+            _ => return None,
+        };
+
+        tool.path
+            .push(ucrt.join("bin").join(&ucrt_version).join(host));
+
+        let ucrt_include = ucrt.join("include").join(&ucrt_version);
+        tool.include.push(ucrt_include.join("ucrt"));
+
+        let ucrt_lib = ucrt.join("lib").join(&ucrt_version);
+        tool.libs.push(ucrt_lib.join("ucrt").join(sub));
+
+        if let Some((sdk, version)) = get_sdk10_dir() {
+            tool.path.push(sdk.join("bin").join(host));
+            let sdk_lib = sdk.join("lib").join(&version);
+            tool.libs.push(sdk_lib.join("um").join(sub));
+            let sdk_include = sdk.join("include").join(&version);
+            tool.include.push(sdk_include.join("um"));
+            tool.include.push(sdk_include.join("cppwinrt"));
+            tool.include.push(sdk_include.join("winrt"));
+            tool.include.push(sdk_include.join("shared"));
+        } else if let Some(sdk) = get_sdk81_dir() {
+            tool.path.push(sdk.join("bin").join(host));
+            let sdk_lib = sdk.join("lib").join("winv6.3");
+            tool.libs.push(sdk_lib.join("um").join(sub));
+            let sdk_include = sdk.join("include");
+            tool.include.push(sdk_include.join("um"));
+            tool.include.push(sdk_include.join("winrt"));
+            tool.include.push(sdk_include.join("shared"));
+        }
+
+        Some(())
+    }
+
+    // For MSVC 12 we need to find the Windows 8.1 SDK.
+    pub fn find_msvc_12(tool: &str, target: &str) -> Option<Tool> {
+        let vcdir = get_vc_dir("12.0")?;
+        let mut tool = get_tool(tool, &vcdir, target)?;
+        let sub = lib_subdir(target)?;
+        let sdk81 = get_sdk81_dir()?;
+        tool.path.push(sdk81.join("bin").join(sub));
+        let sdk_lib = sdk81.join("lib").join("winv6.3");
+        tool.libs.push(sdk_lib.join("um").join(sub));
+        let sdk_include = sdk81.join("include");
+        tool.include.push(sdk_include.join("shared"));
+        tool.include.push(sdk_include.join("um"));
+        tool.include.push(sdk_include.join("winrt"));
+        Some(tool.into_tool())
+    }
+
+    // For MSVC 11 we need to find the Windows 8 SDK.
+    pub fn find_msvc_11(tool: &str, target: &str) -> Option<Tool> {
+        let vcdir = get_vc_dir("11.0")?;
+        let mut tool = get_tool(tool, &vcdir, target)?;
+        let sub = lib_subdir(target)?;
+        let sdk8 = get_sdk8_dir()?;
+        tool.path.push(sdk8.join("bin").join(sub));
+        let sdk_lib = sdk8.join("lib").join("win8");
+        tool.libs.push(sdk_lib.join("um").join(sub));
+        let sdk_include = sdk8.join("include");
+        tool.include.push(sdk_include.join("shared"));
+        tool.include.push(sdk_include.join("um"));
+        tool.include.push(sdk_include.join("winrt"));
+        Some(tool.into_tool())
+    }
+
+    fn add_env(tool: &mut Tool, env: &str, paths: Vec<PathBuf>) {
+        let prev = env::var_os(env).unwrap_or(OsString::new());
+        let prev = env::split_paths(&prev);
+        let new = paths.into_iter().chain(prev);
+        tool.env
+            .push((env.to_string().into(), env::join_paths(new).unwrap()));
+    }
+
+    // Given a possible MSVC installation directory, we look for the linker and
+    // then add the MSVC library path.
+    fn get_tool(tool: &str, path: &Path, target: &str) -> Option<MsvcTool> {
+        bin_subdir(target)
+            .into_iter()
+            .map(|(sub, host)| {
+                (
+                    path.join("bin").join(sub).join(tool),
+                    path.join("bin").join(host),
+                )
+            })
+            .filter(|&(ref path, _)| path.is_file())
+            .map(|(path, host)| {
+                let mut tool = MsvcTool::new(path);
+                tool.path.push(host);
+                tool
+            })
+            .filter_map(|mut tool| {
+                let sub = vc_lib_subdir(target)?;
+                tool.libs.push(path.join("lib").join(sub));
+                tool.include.push(path.join("include"));
+                let atlmfc_path = path.join("atlmfc");
+                if atlmfc_path.exists() {
+                    tool.libs.push(atlmfc_path.join("lib").join(sub));
+                    tool.include.push(atlmfc_path.join("include"));
+                }
+                Some(tool)
+            })
+            .next()
+    }
+
+    // To find MSVC we look in a specific registry key for the version we are
+    // trying to find.
+    fn get_vc_dir(ver: &str) -> Option<PathBuf> {
+        let key = r"SOFTWARE\Microsoft\VisualStudio\SxS\VC7";
+        let key = LOCAL_MACHINE.open(key.as_ref()).ok()?;
+        let path = key.query_str(ver).ok()?;
+        Some(path.into())
+    }
+
+    // To find the Universal CRT we look in a specific registry key for where
+    // all the Universal CRTs are located and then sort them asciibetically to
+    // find the newest version. While this sort of sorting isn't ideal,  it is
+    // what vcvars does so that's good enough for us.
+    //
+    // Returns a pair of (root, version) for the ucrt dir if found
+    fn get_ucrt_dir() -> Option<(PathBuf, String)> {
+        let key = r"SOFTWARE\Microsoft\Windows Kits\Installed Roots";
+        let key = LOCAL_MACHINE.open(key.as_ref()).ok()?;
+        let root = key.query_str("KitsRoot10").ok()?;
+        let readdir = Path::new(&root).join("lib").read_dir().ok()?;
+        let max_libdir = readdir
+            .filter_map(|dir| dir.ok())
+            .map(|dir| dir.path())
+            .filter(|dir| {
+                dir.components()
+                    .last()
+                    .and_then(|c| c.as_os_str().to_str())
+                    .map(|c| c.starts_with("10.") && dir.join("ucrt").is_dir())
+                    .unwrap_or(false)
+            })
+            .max()?;
+        let version = max_libdir.components().last().unwrap();
+        let version = version.as_os_str().to_str().unwrap().to_string();
+        Some((root.into(), version))
+    }
+
+    // Vcvars finds the correct version of the Windows 10 SDK by looking
+    // for the include `um\Windows.h` because sometimes a given version will
+    // only have UCRT bits without the rest of the SDK. Since we only care about
+    // libraries and not includes, we instead look for `um\x64\kernel32.lib`.
+    // Since the 32-bit and 64-bit libraries are always installed together we
+    // only need to bother checking x64, making this code a tiny bit simpler.
+    // Like we do for the Universal CRT, we sort the possibilities
+    // asciibetically to find the newest one as that is what vcvars does.
+    // Before doing that, we check the "WindowsSdkDir" and "WindowsSDKVersion"
+    // environment variables set by vcvars to use the environment sdk version
+    // if one is already configured.
+    fn get_sdk10_dir() -> Option<(PathBuf, String)> {
+        if let (Ok(root), Ok(version)) = (env::var("WindowsSdkDir"), env::var("WindowsSDKVersion"))
+        {
+            return Some((root.into(), version.trim_end_matches('\\').to_string()));
+        }
+
+        let key = r"SOFTWARE\Microsoft\Microsoft SDKs\Windows\v10.0";
+        let key = LOCAL_MACHINE.open(key.as_ref()).ok()?;
+        let root = key.query_str("InstallationFolder").ok()?;
+        let readdir = Path::new(&root).join("lib").read_dir().ok()?;
+        let mut dirs = readdir
+            .filter_map(|dir| dir.ok())
+            .map(|dir| dir.path())
+            .collect::<Vec<_>>();
+        dirs.sort();
+        let dir = dirs
+            .into_iter()
+            .rev()
+            .filter(|dir| dir.join("um").join("x64").join("kernel32.lib").is_file())
+            .next()?;
+        let version = dir.components().last().unwrap();
+        let version = version.as_os_str().to_str().unwrap().to_string();
+        Some((root.into(), version))
+    }
+
+    // Interestingly there are several subdirectories, `win7` `win8` and
+    // `winv6.3`. Vcvars seems to only care about `winv6.3` though, so the same
+    // applies to us. Note that if we were targeting kernel mode drivers
+    // instead of user mode applications, we would care.
+    fn get_sdk81_dir() -> Option<PathBuf> {
+        let key = r"SOFTWARE\Microsoft\Microsoft SDKs\Windows\v8.1";
+        let key = LOCAL_MACHINE.open(key.as_ref()).ok()?;
+        let root = key.query_str("InstallationFolder").ok()?;
+        Some(root.into())
+    }
+
+    fn get_sdk8_dir() -> Option<PathBuf> {
+        let key = r"SOFTWARE\Microsoft\Microsoft SDKs\Windows\v8.0";
+        let key = LOCAL_MACHINE.open(key.as_ref()).ok()?;
+        let root = key.query_str("InstallationFolder").ok()?;
+        Some(root.into())
+    }
+
+    const PROCESSOR_ARCHITECTURE_INTEL: u16 = 0;
+    const PROCESSOR_ARCHITECTURE_AMD64: u16 = 9;
+    const PROCESSOR_ARCHITECTURE_ARM64: u16 = 12;
+    const X86: u16 = PROCESSOR_ARCHITECTURE_INTEL;
+    const X86_64: u16 = PROCESSOR_ARCHITECTURE_AMD64;
+    const AARCH64: u16 = PROCESSOR_ARCHITECTURE_ARM64;
+
+    // When choosing the tool to use, we have to choose the one which matches
+    // the target architecture. Otherwise we end up in situations where someone
+    // on 32-bit Windows is trying to cross compile to 64-bit and it tries to
+    // invoke the native 64-bit compiler which won't work.
+    //
+    // For the return value of this function, the first member of the tuple is
+    // the folder of the tool we will be invoking, while the second member is
+    // the folder of the host toolchain for that tool which is essential when
+    // using a cross linker. We return a Vec since on x64 there are often two
+    // linkers that can target the architecture we desire. The 64-bit host
+    // linker is preferred, and hence first, due to 64-bit allowing it more
+    // address space to work with and potentially being faster.
+    fn bin_subdir(target: &str) -> Vec<(&'static str, &'static str)> {
+        let arch = target.split('-').next().unwrap();
+        match (arch, host_arch()) {
+            ("i586", X86) | ("i686", X86) => vec![("", "")],
+            ("i586", X86_64) | ("i686", X86_64) => vec![("amd64_x86", "amd64"), ("", "")],
+            ("x86_64", X86) => vec![("x86_amd64", "")],
+            ("x86_64", X86_64) => vec![("amd64", "amd64"), ("x86_amd64", "")],
+            ("arm", X86) | ("thumbv7a", X86) => vec![("x86_arm", "")],
+            ("arm", X86_64) | ("thumbv7a", X86_64) => vec![("amd64_arm", "amd64"), ("x86_arm", "")],
+            _ => vec![],
+        }
+    }
+
+    fn lib_subdir(target: &str) -> Option<&'static str> {
+        let arch = target.split('-').next().unwrap();
+        match arch {
+            "i586" | "i686" => Some("x86"),
+            "x86_64" => Some("x64"),
+            "arm" | "thumbv7a" => Some("arm"),
+            "aarch64" => Some("arm64"),
+            _ => None,
+        }
+    }
+
+    // MSVC's x86 libraries are not in a subfolder
+    fn vc_lib_subdir(target: &str) -> Option<&'static str> {
+        let arch = target.split('-').next().unwrap();
+        match arch {
+            "i586" | "i686" => Some(""),
+            "x86_64" => Some("amd64"),
+            "arm" | "thumbv7a" => Some("arm"),
+            "aarch64" => Some("arm64"),
+            _ => None,
+        }
+    }
+
+    #[allow(bad_style)]
+    fn host_arch() -> u16 {
+        type DWORD = u32;
+        type WORD = u16;
+        type LPVOID = *mut u8;
+        type DWORD_PTR = usize;
+
+        #[repr(C)]
+        struct SYSTEM_INFO {
+            wProcessorArchitecture: WORD,
+            _wReserved: WORD,
+            _dwPageSize: DWORD,
+            _lpMinimumApplicationAddress: LPVOID,
+            _lpMaximumApplicationAddress: LPVOID,
+            _dwActiveProcessorMask: DWORD_PTR,
+            _dwNumberOfProcessors: DWORD,
+            _dwProcessorType: DWORD,
+            _dwAllocationGranularity: DWORD,
+            _wProcessorLevel: WORD,
+            _wProcessorRevision: WORD,
+        }
+
+        extern "system" {
+            fn GetNativeSystemInfo(lpSystemInfo: *mut SYSTEM_INFO);
+        }
+
+        unsafe {
+            let mut info = mem::zeroed();
+            GetNativeSystemInfo(&mut info);
+            info.wProcessorArchitecture
+        }
+    }
+
+    // Given a registry key, look at all the sub keys and find the one which has
+    // the maximal numeric value.
+    //
+    // Returns the name of the maximal key as well as the opened maximal key.
+    fn max_version(key: &RegistryKey) -> Option<(OsString, RegistryKey)> {
+        let mut max_vers = 0;
+        let mut max_key = None;
+        for subkey in key.iter().filter_map(|k| k.ok()) {
+            let val = subkey
+                .to_str()
+                .and_then(|s| s.trim_left_matches("v").replace(".", "").parse().ok());
+            let val = match val {
+                Some(s) => s,
+                None => continue,
+            };
+            if val > max_vers {
+                if let Ok(k) = key.open(&subkey) {
+                    max_vers = val;
+                    max_key = Some((subkey, k));
+                }
+            }
+        }
+        max_key
+    }
+
+    pub fn has_msbuild_version(version: &str) -> bool {
+        match version {
+            "17.0" => {
+                find_msbuild_vs17("x86_64-pc-windows-msvc").is_some()
+                    || find_msbuild_vs17("i686-pc-windows-msvc").is_some()
+                    || find_msbuild_vs17("aarch64-pc-windows-msvc").is_some()
+            }
+            "16.0" => {
+                find_msbuild_vs16("x86_64-pc-windows-msvc").is_some()
+                    || find_msbuild_vs16("i686-pc-windows-msvc").is_some()
+                    || find_msbuild_vs16("aarch64-pc-windows-msvc").is_some()
+            }
+            "15.0" => {
+                find_msbuild_vs15("x86_64-pc-windows-msvc").is_some()
+                    || find_msbuild_vs15("i686-pc-windows-msvc").is_some()
+                    || find_msbuild_vs15("aarch64-pc-windows-msvc").is_some()
+            }
+            "12.0" | "14.0" => LOCAL_MACHINE
+                .open(&OsString::from(format!(
+                    "SOFTWARE\\Microsoft\\MSBuild\\ToolsVersions\\{}",
+                    version
+                )))
+                .is_ok(),
+            _ => false,
+        }
+    }
+
+    pub fn find_devenv(target: &str) -> Option<Tool> {
+        find_devenv_vs15(&target)
+    }
+
+    fn find_devenv_vs15(target: &str) -> Option<Tool> {
+        find_tool_in_vs15_path(r"Common7\IDE\devenv.exe", target)
+    }
+
+    // see http://stackoverflow.com/questions/328017/path-to-msbuild
+    pub fn find_msbuild(target: &str) -> Option<Tool> {
+        // VS 15 (2017) changed how to locate msbuild
+        if let Some(r) = find_msbuild_vs17(target) {
+            return Some(r);
+        } else if let Some(r) = find_msbuild_vs16(target) {
+            return Some(r);
+        } else if let Some(r) = find_msbuild_vs15(target) {
+            return Some(r);
+        } else {
+            find_old_msbuild(target)
+        }
+    }
+
+    fn find_msbuild_vs15(target: &str) -> Option<Tool> {
+        find_tool_in_vs15_path(r"MSBuild\15.0\Bin\MSBuild.exe", target)
+    }
+
+    fn find_old_msbuild(target: &str) -> Option<Tool> {
+        let key = r"SOFTWARE\Microsoft\MSBuild\ToolsVersions";
+        LOCAL_MACHINE
+            .open(key.as_ref())
+            .ok()
+            .and_then(|key| {
+                max_version(&key).and_then(|(_vers, key)| key.query_str("MSBuildToolsPath").ok())
+            })
+            .map(|path| {
+                let mut path = PathBuf::from(path);
+                path.push("MSBuild.exe");
+                let mut tool = Tool::with_family(path, MSVC_FAMILY);
+                if target.contains("x86_64") {
+                    tool.env.push(("Platform".into(), "X64".into()));
+                }
+                tool
+            })
+    }
+}
diff --git a/tests/cc_env.rs b/tests/cc_env.rs
new file mode 100644
index 0000000..43eb689
--- /dev/null
+++ b/tests/cc_env.rs
@@ -0,0 +1,118 @@
+use std::env;
+use std::ffi::OsString;
+use std::path::Path;
+
+mod support;
+use crate::support::Test;
+
+#[test]
+fn main() {
+    ccache();
+    distcc();
+    ccache_spaces();
+    ccache_env_flags();
+    leading_spaces();
+    extra_flags();
+    path_to_ccache();
+    more_spaces();
+}
+
+fn ccache() {
+    let test = Test::gnu();
+
+    env::set_var("CC", "ccache cc");
+    let compiler = test.gcc().file("foo.c").get_compiler();
+
+    assert_eq!(compiler.path(), Path::new("cc"));
+}
+
+fn ccache_spaces() {
+    let test = Test::gnu();
+    test.shim("ccache");
+
+    env::set_var("CC", "ccache        cc");
+    let compiler = test.gcc().file("foo.c").get_compiler();
+    assert_eq!(compiler.path(), Path::new("cc"));
+}
+
+fn distcc() {
+    let test = Test::gnu();
+    test.shim("distcc");
+
+    env::set_var("CC", "distcc cc");
+    let compiler = test.gcc().file("foo.c").get_compiler();
+    assert_eq!(compiler.path(), Path::new("cc"));
+}
+
+fn ccache_env_flags() {
+    let test = Test::gnu();
+    test.shim("ccache");
+
+    env::set_var("CC", "ccache lol-this-is-not-a-compiler");
+    let compiler = test.gcc().file("foo.c").get_compiler();
+    assert_eq!(compiler.path(), Path::new("lol-this-is-not-a-compiler"));
+    assert_eq!(
+        compiler.cc_env(),
+        OsString::from("ccache lol-this-is-not-a-compiler")
+    );
+    assert!(
+        compiler
+            .cflags_env()
+            .into_string()
+            .unwrap()
+            .contains("ccache")
+            == false
+    );
+    assert!(
+        compiler
+            .cflags_env()
+            .into_string()
+            .unwrap()
+            .contains(" lol-this-is-not-a-compiler")
+            == false
+    );
+
+    env::set_var("CC", "");
+}
+
+fn leading_spaces() {
+    let test = Test::gnu();
+    test.shim("ccache");
+
+    env::set_var("CC", " test ");
+    let compiler = test.gcc().file("foo.c").get_compiler();
+    assert_eq!(compiler.path(), Path::new("test"));
+
+    env::set_var("CC", "");
+}
+
+fn extra_flags() {
+    let test = Test::gnu();
+    test.shim("ccache");
+
+    env::set_var("CC", "ccache cc -m32");
+    let compiler = test.gcc().file("foo.c").get_compiler();
+    assert_eq!(compiler.path(), Path::new("cc"));
+}
+
+fn path_to_ccache() {
+    let test = Test::gnu();
+    test.shim("ccache");
+
+    env::set_var("CC", "/path/to/ccache.exe cc -m32");
+    let compiler = test.gcc().file("foo.c").get_compiler();
+    assert_eq!(compiler.path(), Path::new("cc"));
+    assert_eq!(
+        compiler.cc_env(),
+        OsString::from("/path/to/ccache.exe cc -m32"),
+    );
+}
+
+fn more_spaces() {
+    let test = Test::gnu();
+    test.shim("ccache");
+
+    env::set_var("CC", "cc -m32");
+    let compiler = test.gcc().file("foo.c").get_compiler();
+    assert_eq!(compiler.path(), Path::new("cc"));
+}
diff --git a/tests/cflags.rs b/tests/cflags.rs
new file mode 100644
index 0000000..caec6ea
--- /dev/null
+++ b/tests/cflags.rs
@@ -0,0 +1,15 @@
+mod support;
+
+use crate::support::Test;
+use std::env;
+
+/// This test is in its own module because it modifies the environment and would affect other tests
+/// when run in parallel with them.
+#[test]
+fn gnu_no_warnings_if_cflags() {
+    env::set_var("CFLAGS", "-arbitrary");
+    let test = Test::gnu();
+    test.gcc().file("foo.c").compile("foo");
+
+    test.cmd(0).must_not_have("-Wall").must_not_have("-Wextra");
+}
diff --git a/tests/cxxflags.rs b/tests/cxxflags.rs
new file mode 100644
index 0000000..c524c7d
--- /dev/null
+++ b/tests/cxxflags.rs
@@ -0,0 +1,15 @@
+mod support;
+
+use crate::support::Test;
+use std::env;
+
+/// This test is in its own module because it modifies the environment and would affect other tests
+/// when run in parallel with them.
+#[test]
+fn gnu_no_warnings_if_cxxflags() {
+    env::set_var("CXXFLAGS", "-arbitrary");
+    let test = Test::gnu();
+    test.gcc().file("foo.cpp").cpp(true).compile("foo");
+
+    test.cmd(0).must_not_have("-Wall").must_not_have("-Wextra");
+}
diff --git a/tests/support/mod.rs b/tests/support/mod.rs
new file mode 100644
index 0000000..f3c0440
--- /dev/null
+++ b/tests/support/mod.rs
@@ -0,0 +1,172 @@
+#![allow(dead_code)]
+
+use std::env;
+use std::ffi::{OsStr, OsString};
+use std::fs::{self, File};
+use std::io;
+use std::io::prelude::*;
+use std::path::{Path, PathBuf};
+
+use cc;
+use tempfile::{Builder, TempDir};
+
+pub struct Test {
+    pub td: TempDir,
+    pub gcc: PathBuf,
+    pub msvc: bool,
+}
+
+pub struct Execution {
+    args: Vec<String>,
+}
+
+impl Test {
+    pub fn new() -> Test {
+        // This is ugly: `sccache` needs to introspect the compiler it is
+        // executing, as it adjusts its behavior depending on the
+        // language/compiler. This crate's test driver uses mock compilers that
+        // are obviously not supported by sccache, so the tests fail if
+        // RUSTC_WRAPPER is set. rust doesn't build test dependencies with
+        // the `test` feature enabled, so we can't conditionally disable the
+        // usage of `sccache` if running in a test environment, at least not
+        // without setting an environment variable here and testing for it
+        // there. Explicitly deasserting RUSTC_WRAPPER here seems to be the
+        // lesser of the two evils.
+        env::remove_var("RUSTC_WRAPPER");
+
+        let mut gcc = PathBuf::from(env::current_exe().unwrap());
+        gcc.pop();
+        if gcc.ends_with("deps") {
+            gcc.pop();
+        }
+        let td = Builder::new().prefix("gcc-test").tempdir_in(&gcc).unwrap();
+        gcc.push(format!("gcc-shim{}", env::consts::EXE_SUFFIX));
+        Test {
+            td: td,
+            gcc: gcc,
+            msvc: false,
+        }
+    }
+
+    pub fn gnu() -> Test {
+        let t = Test::new();
+        t.shim("cc").shim("c++").shim("ar");
+        t
+    }
+
+    pub fn msvc() -> Test {
+        let mut t = Test::new();
+        t.shim("cl").shim("lib.exe");
+        t.msvc = true;
+        t
+    }
+
+    pub fn shim(&self, name: &str) -> &Test {
+        let name = if name.ends_with(env::consts::EXE_SUFFIX) {
+            name.to_string()
+        } else {
+            format!("{}{}", name, env::consts::EXE_SUFFIX)
+        };
+        link_or_copy(&self.gcc, self.td.path().join(name)).unwrap();
+        self
+    }
+
+    pub fn gcc(&self) -> cc::Build {
+        let mut cfg = cc::Build::new();
+        let target = if self.msvc {
+            "x86_64-pc-windows-msvc"
+        } else {
+            "x86_64-unknown-linux-gnu"
+        };
+
+        cfg.target(target)
+            .host(target)
+            .opt_level(2)
+            .debug(false)
+            .out_dir(self.td.path())
+            .__set_env("PATH", self.path())
+            .__set_env("GCCTEST_OUT_DIR", self.td.path());
+        if self.msvc {
+            cfg.compiler(self.td.path().join("cl"));
+            cfg.archiver(self.td.path().join("lib.exe"));
+        }
+        cfg
+    }
+
+    fn path(&self) -> OsString {
+        let mut path = env::split_paths(&env::var_os("PATH").unwrap()).collect::<Vec<_>>();
+        path.insert(0, self.td.path().to_owned());
+        env::join_paths(path).unwrap()
+    }
+
+    pub fn cmd(&self, i: u32) -> Execution {
+        let mut s = String::new();
+        File::open(self.td.path().join(format!("out{}", i)))
+            .unwrap()
+            .read_to_string(&mut s)
+            .unwrap();
+        Execution {
+            args: s.lines().map(|s| s.to_string()).collect(),
+        }
+    }
+}
+
+impl Execution {
+    pub fn must_have<P: AsRef<OsStr>>(&self, p: P) -> &Execution {
+        if !self.has(p.as_ref()) {
+            panic!("didn't find {:?} in {:?}", p.as_ref(), self.args);
+        } else {
+            self
+        }
+    }
+
+    pub fn must_not_have<P: AsRef<OsStr>>(&self, p: P) -> &Execution {
+        if self.has(p.as_ref()) {
+            panic!("found {:?}", p.as_ref());
+        } else {
+            self
+        }
+    }
+
+    pub fn has(&self, p: &OsStr) -> bool {
+        self.args.iter().any(|arg| OsStr::new(arg) == p)
+    }
+
+    pub fn must_have_in_order(&self, before: &str, after: &str) -> &Execution {
+        let before_position = self
+            .args
+            .iter()
+            .rposition(|x| OsStr::new(x) == OsStr::new(before));
+        let after_position = self
+            .args
+            .iter()
+            .rposition(|x| OsStr::new(x) == OsStr::new(after));
+        match (before_position, after_position) {
+            (Some(b), Some(a)) if b < a => {}
+            (b, a) => panic!(
+                "{:?} (last position: {:?}) did not appear before {:?} (last position: {:?})",
+                before, b, after, a
+            ),
+        };
+        self
+    }
+}
+
+/// Hard link an executable or copy it if that fails.
+///
+/// We first try to hard link an executable to save space. If that fails (as on Windows with
+/// different mount points, issue #60), we copy.
+#[cfg(not(target_os = "macos"))]
+fn link_or_copy<P: AsRef<Path>, Q: AsRef<Path>>(from: P, to: Q) -> io::Result<()> {
+    let from = from.as_ref();
+    let to = to.as_ref();
+    fs::hard_link(from, to).or_else(|_| fs::copy(from, to).map(|_| ()))
+}
+
+/// Copy an executable.
+///
+/// On macOS, hard linking the executable leads to strange failures (issue #419), so we just copy.
+#[cfg(target_os = "macos")]
+fn link_or_copy<P: AsRef<Path>, Q: AsRef<Path>>(from: P, to: Q) -> io::Result<()> {
+    fs::copy(from, to).map(|_| ())
+}
diff --git a/tests/test.rs b/tests/test.rs
new file mode 100644
index 0000000..161abd8
--- /dev/null
+++ b/tests/test.rs
@@ -0,0 +1,461 @@
+use crate::support::Test;
+
+mod support;
+
+// Some tests check that a flag is *not* present.  These tests might fail if the flag is set in the
+// CFLAGS or CXXFLAGS environment variables.  This function clears the CFLAGS and CXXFLAGS
+// variables to make sure that the tests can run correctly.
+fn reset_env() {
+    std::env::set_var("CFLAGS", "");
+    std::env::set_var("CXXFLAGS", "");
+}
+
+#[test]
+fn gnu_smoke() {
+    reset_env();
+
+    let test = Test::gnu();
+    test.gcc().file("foo.c").compile("foo");
+
+    test.cmd(0)
+        .must_have("-O2")
+        .must_have("foo.c")
+        .must_not_have("-gdwarf-4")
+        .must_have("-c")
+        .must_have("-ffunction-sections")
+        .must_have("-fdata-sections");
+    test.cmd(1).must_have(test.td.path().join("foo.o"));
+}
+
+#[test]
+fn gnu_opt_level_1() {
+    reset_env();
+
+    let test = Test::gnu();
+    test.gcc().opt_level(1).file("foo.c").compile("foo");
+
+    test.cmd(0).must_have("-O1").must_not_have("-O2");
+}
+
+#[test]
+fn gnu_opt_level_s() {
+    reset_env();
+
+    let test = Test::gnu();
+    test.gcc().opt_level_str("s").file("foo.c").compile("foo");
+
+    test.cmd(0)
+        .must_have("-Os")
+        .must_not_have("-O1")
+        .must_not_have("-O2")
+        .must_not_have("-O3")
+        .must_not_have("-Oz");
+}
+
+#[test]
+fn gnu_debug() {
+    let test = Test::gnu();
+    test.gcc().debug(true).file("foo.c").compile("foo");
+    test.cmd(0).must_have("-gdwarf-4");
+
+    let test = Test::gnu();
+    test.gcc()
+        .target("x86_64-apple-darwin")
+        .debug(true)
+        .file("foo.c")
+        .compile("foo");
+    test.cmd(0).must_have("-gdwarf-2");
+}
+
+#[test]
+fn gnu_debug_fp_auto() {
+    let test = Test::gnu();
+    test.gcc().debug(true).file("foo.c").compile("foo");
+    test.cmd(0).must_have("-gdwarf-4");
+    test.cmd(0).must_have("-fno-omit-frame-pointer");
+}
+
+#[test]
+fn gnu_debug_fp() {
+    let test = Test::gnu();
+    test.gcc().debug(true).file("foo.c").compile("foo");
+    test.cmd(0).must_have("-gdwarf-4");
+    test.cmd(0).must_have("-fno-omit-frame-pointer");
+}
+
+#[test]
+fn gnu_debug_nofp() {
+    reset_env();
+
+    let test = Test::gnu();
+    test.gcc()
+        .debug(true)
+        .force_frame_pointer(false)
+        .file("foo.c")
+        .compile("foo");
+    test.cmd(0).must_have("-gdwarf-4");
+    test.cmd(0).must_not_have("-fno-omit-frame-pointer");
+
+    let test = Test::gnu();
+    test.gcc()
+        .force_frame_pointer(false)
+        .debug(true)
+        .file("foo.c")
+        .compile("foo");
+    test.cmd(0).must_have("-gdwarf-4");
+    test.cmd(0).must_not_have("-fno-omit-frame-pointer");
+}
+
+#[test]
+fn gnu_warnings_into_errors() {
+    let test = Test::gnu();
+    test.gcc()
+        .warnings_into_errors(true)
+        .file("foo.c")
+        .compile("foo");
+
+    test.cmd(0).must_have("-Werror");
+}
+
+#[test]
+fn gnu_warnings() {
+    let test = Test::gnu();
+    test.gcc()
+        .warnings(true)
+        .flag("-Wno-missing-field-initializers")
+        .file("foo.c")
+        .compile("foo");
+
+    test.cmd(0).must_have("-Wall").must_have("-Wextra");
+}
+
+#[test]
+fn gnu_extra_warnings0() {
+    reset_env();
+
+    let test = Test::gnu();
+    test.gcc()
+        .warnings(true)
+        .extra_warnings(false)
+        .flag("-Wno-missing-field-initializers")
+        .file("foo.c")
+        .compile("foo");
+
+    test.cmd(0).must_have("-Wall").must_not_have("-Wextra");
+}
+
+#[test]
+fn gnu_extra_warnings1() {
+    reset_env();
+
+    let test = Test::gnu();
+    test.gcc()
+        .warnings(false)
+        .extra_warnings(true)
+        .flag("-Wno-missing-field-initializers")
+        .file("foo.c")
+        .compile("foo");
+
+    test.cmd(0).must_not_have("-Wall").must_have("-Wextra");
+}
+
+#[test]
+fn gnu_warnings_overridable() {
+    reset_env();
+
+    let test = Test::gnu();
+    test.gcc()
+        .warnings(true)
+        .flag("-Wno-missing-field-initializers")
+        .file("foo.c")
+        .compile("foo");
+
+    test.cmd(0)
+        .must_have_in_order("-Wall", "-Wno-missing-field-initializers");
+}
+
+#[test]
+fn gnu_x86_64() {
+    for vendor in &["unknown-linux-gnu", "apple-darwin"] {
+        let target = format!("x86_64-{}", vendor);
+        let test = Test::gnu();
+        test.gcc()
+            .target(&target)
+            .host(&target)
+            .file("foo.c")
+            .compile("foo");
+
+        test.cmd(0).must_have("-fPIC").must_have("-m64");
+    }
+}
+
+#[test]
+fn gnu_x86_64_no_pic() {
+    reset_env();
+
+    for vendor in &["unknown-linux-gnu", "apple-darwin"] {
+        let target = format!("x86_64-{}", vendor);
+        let test = Test::gnu();
+        test.gcc()
+            .pic(false)
+            .target(&target)
+            .host(&target)
+            .file("foo.c")
+            .compile("foo");
+
+        test.cmd(0).must_not_have("-fPIC");
+    }
+}
+
+#[test]
+fn gnu_i686() {
+    for vendor in &["unknown-linux-gnu", "apple-darwin"] {
+        let target = format!("i686-{}", vendor);
+        let test = Test::gnu();
+        test.gcc()
+            .target(&target)
+            .host(&target)
+            .file("foo.c")
+            .compile("foo");
+
+        test.cmd(0).must_have("-m32");
+    }
+}
+
+#[test]
+fn gnu_i686_pic() {
+    for vendor in &["unknown-linux-gnu", "apple-darwin"] {
+        let target = format!("i686-{}", vendor);
+        let test = Test::gnu();
+        test.gcc()
+            .pic(true)
+            .target(&target)
+            .host(&target)
+            .file("foo.c")
+            .compile("foo");
+
+        test.cmd(0).must_have("-fPIC");
+    }
+}
+
+#[test]
+fn gnu_x86_64_no_plt() {
+    let target = "x86_64-unknown-linux-gnu";
+    let test = Test::gnu();
+    test.gcc()
+        .pic(true)
+        .use_plt(false)
+        .target(&target)
+        .host(&target)
+        .file("foo.c")
+        .compile("foo");
+    test.cmd(0).must_have("-fno-plt");
+}
+
+#[test]
+fn gnu_set_stdlib() {
+    reset_env();
+
+    let test = Test::gnu();
+    test.gcc()
+        .cpp_set_stdlib(Some("foo"))
+        .file("foo.c")
+        .compile("foo");
+
+    test.cmd(0).must_not_have("-stdlib=foo");
+}
+
+#[test]
+fn gnu_include() {
+    let test = Test::gnu();
+    test.gcc().include("foo/bar").file("foo.c").compile("foo");
+
+    test.cmd(0).must_have("-I").must_have("foo/bar");
+}
+
+#[test]
+fn gnu_define() {
+    let test = Test::gnu();
+    test.gcc()
+        .define("FOO", "bar")
+        .define("BAR", None)
+        .file("foo.c")
+        .compile("foo");
+
+    test.cmd(0).must_have("-DFOO=bar").must_have("-DBAR");
+}
+
+#[test]
+fn gnu_compile_assembly() {
+    let test = Test::gnu();
+    test.gcc().file("foo.S").compile("foo");
+    test.cmd(0).must_have("foo.S");
+}
+
+#[test]
+fn gnu_shared() {
+    reset_env();
+
+    let test = Test::gnu();
+    test.gcc()
+        .file("foo.c")
+        .shared_flag(true)
+        .static_flag(false)
+        .compile("foo");
+
+    test.cmd(0).must_have("-shared").must_not_have("-static");
+}
+
+#[test]
+fn gnu_flag_if_supported() {
+    reset_env();
+
+    if cfg!(windows) {
+        return;
+    }
+    let test = Test::gnu();
+    test.gcc()
+        .file("foo.c")
+        .flag("-v")
+        .flag_if_supported("-Wall")
+        .flag_if_supported("-Wflag-does-not-exist")
+        .flag_if_supported("-std=c++11")
+        .compile("foo");
+
+    test.cmd(0)
+        .must_have("-v")
+        .must_have("-Wall")
+        .must_not_have("-Wflag-does-not-exist")
+        .must_not_have("-std=c++11");
+}
+
+#[test]
+fn gnu_flag_if_supported_cpp() {
+    if cfg!(windows) {
+        return;
+    }
+    let test = Test::gnu();
+    test.gcc()
+        .cpp(true)
+        .file("foo.cpp")
+        .flag_if_supported("-std=c++11")
+        .compile("foo");
+
+    test.cmd(0).must_have("-std=c++11");
+}
+
+#[test]
+fn gnu_static() {
+    reset_env();
+
+    let test = Test::gnu();
+    test.gcc()
+        .file("foo.c")
+        .shared_flag(false)
+        .static_flag(true)
+        .compile("foo");
+
+    test.cmd(0).must_have("-static").must_not_have("-shared");
+}
+
+#[test]
+fn gnu_no_dash_dash() {
+    let test = Test::gnu();
+    test.gcc().file("foo.c").compile("foo");
+
+    test.cmd(0).must_not_have("--");
+}
+
+#[test]
+fn msvc_smoke() {
+    reset_env();
+
+    let test = Test::msvc();
+    test.gcc().file("foo.c").compile("foo");
+
+    test.cmd(0)
+        .must_have("-O2")
+        .must_have("foo.c")
+        .must_not_have("-Z7")
+        .must_have("-c")
+        .must_have("-MD");
+    test.cmd(1).must_have(test.td.path().join("foo.o"));
+}
+
+#[test]
+fn msvc_opt_level_0() {
+    reset_env();
+
+    let test = Test::msvc();
+    test.gcc().opt_level(0).file("foo.c").compile("foo");
+
+    test.cmd(0).must_not_have("-O2");
+}
+
+#[test]
+fn msvc_debug() {
+    let test = Test::msvc();
+    test.gcc().debug(true).file("foo.c").compile("foo");
+    test.cmd(0).must_have("-Z7");
+}
+
+#[test]
+fn msvc_include() {
+    let test = Test::msvc();
+    test.gcc().include("foo/bar").file("foo.c").compile("foo");
+
+    test.cmd(0).must_have("-I").must_have("foo/bar");
+}
+
+#[test]
+fn msvc_define() {
+    let test = Test::msvc();
+    test.gcc()
+        .define("FOO", "bar")
+        .define("BAR", None)
+        .file("foo.c")
+        .compile("foo");
+
+    test.cmd(0).must_have("-DFOO=bar").must_have("-DBAR");
+}
+
+#[test]
+fn msvc_static_crt() {
+    let test = Test::msvc();
+    test.gcc().static_crt(true).file("foo.c").compile("foo");
+
+    test.cmd(0).must_have("-MT");
+}
+
+#[test]
+fn msvc_no_static_crt() {
+    let test = Test::msvc();
+    test.gcc().static_crt(false).file("foo.c").compile("foo");
+
+    test.cmd(0).must_have("-MD");
+}
+
+#[test]
+fn msvc_no_dash_dash() {
+    let test = Test::msvc();
+    test.gcc().file("foo.c").compile("foo");
+
+    test.cmd(0).must_not_have("--");
+}
+
+// Disable this test with the parallel feature because the execution
+// order is not deterministic.
+#[cfg(not(feature = "parallel"))]
+#[test]
+fn asm_flags() {
+    let test = Test::gnu();
+    test.gcc()
+        .file("foo.c")
+        .file("x86_64.asm")
+        .file("x86_64.S")
+        .asm_flag("--abc")
+        .compile("foo");
+    test.cmd(0).must_not_have("--abc");
+    test.cmd(1).must_have("--abc");
+    test.cmd(2).must_have("--abc");
+}