[EventPipe] Fix linker warning on Debug/Checked build and unlink Unix Domain Socket #23334 (#23357)

- Attempt to close-behind unix domain socket and repurpose LF_REMOTING facility.
  - On shutdown, attempt to unlink the bound socket so it can be removed from the file system when the last reference to it it closed.
- Rename unused LF_REMOTING to LF_DIAGNOSTICS_PORT. This new flag will be used by the diagnostic server stress log calls.
- libcmtd.lib(initializers.obj) : warning LNK4098: defaultlib 'libcmt.lib' conflicts with use of other libs; use /NODEFAULTLIB:library [S:\github.com\jorive\coreclr\bin\obj\Windows_NT.x64.Checked\src\dlls\mscoree\coreclr\coreclr.vcxproj]
- Move some preprocessors and includes around.

4 files changed, 65 insertions, 13 deletions

diff --git a/src/debug/debug-pal/CMakeLists.txt b/src/debug/debug-pal/CMakeLists.txt
index c1b5b443a9..ac0f97e468 100644
--- a/src/debug/debug-pal/CMakeLists.txt
+++ b/src/debug/debug-pal/CMakeLists.txt
@@ -5,12 +5,10 @@ include_directories(../../pal/inc)
 add_definitions(-DPAL_STDCPP_COMPAT=1)
 
 if(WIN32)
-    #use static crt
-    add_definitions(-MT) 
     add_definitions(-DWIN32_LEAN_AND_MEAN)
     include_directories(../../inc) #needed for warning control
 
-    set(TWO_WAY_PIPE_SOURCES 
+    set(TWO_WAY_PIPE_SOURCES
         win/diagnosticsipc.cpp
         win/twowaypipe.cpp
         win/processdescriptor.cpp
diff --git a/src/debug/debug-pal/unix/diagnosticsipc.cpp b/src/debug/debug-pal/unix/diagnosticsipc.cpp
index 182dff01be..d9e0e94c9f 100644
--- a/src/debug/debug-pal/unix/diagnosticsipc.cpp
+++ b/src/debug/debug-pal/unix/diagnosticsipc.cpp
@@ -7,7 +7,6 @@
 #include <new>
 #include <unistd.h>
 #include <fcntl.h>
-#include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/un.h>
 #include "diagnosticsipc.h"
@@ -15,7 +14,8 @@
 
 IpcStream::DiagnosticsIpc::DiagnosticsIpc(const int serverSocket, sockaddr_un *const pServerAddress) :
     _serverSocket(serverSocket),
-    _pServerAddress(new (std::nothrow) sockaddr_un)
+    _pServerAddress(new (std::nothrow) sockaddr_un),
+    _isUnlinked(false)
 {
     _ASSERTE(_pServerAddress != nullptr);
     _ASSERTE(_serverSocket != -1);
@@ -33,8 +33,7 @@ IpcStream::DiagnosticsIpc::~DiagnosticsIpc()
         const int fSuccessClose = ::close(_serverSocket);
         _ASSERTE(fSuccessClose != -1); // TODO: Add error handling?
 
-        const int fSuccessUnlink = ::unlink(_pServerAddress->sun_path);
-        _ASSERTE(fSuccessUnlink != -1); // TODO: Add error handling?
+        Unlink();
 
         delete _pServerAddress;
     }
@@ -68,6 +67,26 @@ IpcStream::DiagnosticsIpc *IpcStream::DiagnosticsIpc::Create(const char *const p
         if (callback != nullptr)
             callback(strerror(errno), errno);
         _ASSERTE(fSuccessBind != -1);
+
+        const int fSuccessClose = ::close(serverSocket);
+        _ASSERTE(fSuccessClose != -1);
+
+        return nullptr;
+    }
+
+    const int fSuccessfulListen = ::listen(serverSocket, /* backlog */ 255);
+    if (fSuccessfulListen == -1)
+    {
+        if (callback != nullptr)
+            callback(strerror(errno), errno);
+        _ASSERTE(fSuccessfulListen != -1);
+
+        const int fSuccessUnlink = ::unlink(serverAddress.sun_path);
+        _ASSERTE(fSuccessUnlink != -1);
+
+        const int fSuccessClose = ::close(serverSocket);
+        _ASSERTE(fSuccessClose != -1);
+
         return nullptr;
     }
 
@@ -76,8 +95,6 @@ IpcStream::DiagnosticsIpc *IpcStream::DiagnosticsIpc::Create(const char *const p
 
 IpcStream *IpcStream::DiagnosticsIpc::Accept(ErrorCallback callback) const
 {
-    if (::listen(_serverSocket, /* backlog */ 255) == -1)
-        return nullptr;
     sockaddr_un from;
     socklen_t fromlen = sizeof(from);
     const int clientSocket = ::accept(_serverSocket, (sockaddr *)&from, &fromlen);
@@ -94,6 +111,28 @@ IpcStream *IpcStream::DiagnosticsIpc::Accept(ErrorCallback callback) const
     return pIpcStream;
 }
 
+//! This helps remove the socket from the filesystem when the runtime exits.
+//! From: http://man7.org/linux/man-pages/man7/unix.7.html#NOTES
+//!   Binding to a socket with a filename creates a socket in the
+//!   filesystem that must be deleted by the caller when it is no longer
+//!   needed (using unlink(2)).  The usual UNIX close-behind semantics
+//!   apply; the socket can be unlinked at any time and will be finally
+//!   removed from the filesystem when the last reference to it is closed.
+void IpcStream::DiagnosticsIpc::Unlink(ErrorCallback callback)
+{
+    if (_isUnlinked)
+        return;
+    _isUnlinked = true;
+
+    const int fSuccessUnlink = ::unlink(_pServerAddress->sun_path);
+    if (fSuccessUnlink == -1)
+    {
+        if (callback != nullptr)
+            callback(strerror(errno), errno);
+        _ASSERTE(fSuccessUnlink == 0);
+    }
+}
+
 IpcStream::~IpcStream()
 {
     if (_clientSocket != -1)
diff --git a/src/debug/debug-pal/win/diagnosticsipc.cpp b/src/debug/debug-pal/win/diagnosticsipc.cpp
index 7d9f84e7e5..46f212836b 100644
--- a/src/debug/debug-pal/win/diagnosticsipc.cpp
+++ b/src/debug/debug-pal/win/diagnosticsipc.cpp
@@ -77,6 +77,10 @@ IpcStream *IpcStream::DiagnosticsIpc::Accept(ErrorCallback callback) const
     return pIpcStream;
 }
 
+void IpcStream::DiagnosticsIpc::Unlink(ErrorCallback callback)
+{
+}
+
 IpcStream::~IpcStream()
 {
     if (_hPipe != INVALID_HANDLE_VALUE)
diff --git a/src/debug/inc/diagnosticsipc.h b/src/debug/inc/diagnosticsipc.h
index 81789f0803..54277e1af9 100644
--- a/src/debug/inc/diagnosticsipc.h
+++ b/src/debug/inc/diagnosticsipc.h
@@ -26,20 +26,31 @@ public:
     class DiagnosticsIpc final
     {
     public:
-        static DiagnosticsIpc *Create(const char *const pIpcName, ErrorCallback callback = nullptr);
         ~DiagnosticsIpc();
+
+        //! Creates an IPC object
+        static DiagnosticsIpc *Create(const char *const pIpcName, ErrorCallback callback = nullptr);
+
+        //! Enables the underlaying IPC implementation to accept connection.
         IpcStream *Accept(ErrorCallback callback = nullptr) const;
 
+        //! Used to unlink the socket so it can be removed from the filesystem
+        //! when the last reference to it is closed.
+        void Unlink(ErrorCallback callback = nullptr);
+
     private:
 
 #ifdef FEATURE_PAL
-        DiagnosticsIpc(const int serverSocket, sockaddr_un *const pServerAddress);
-        const int _serverSocket = -1;
+        const int _serverSocket;
         sockaddr_un *const _pServerAddress;
+        bool _isUnlinked = false;
+
+        DiagnosticsIpc(const int serverSocket, sockaddr_un *const pServerAddress);
 #else
         static const uint32_t MaxNamedPipeNameLength = 256;
-        DiagnosticsIpc(const char(&namedPipeName)[MaxNamedPipeNameLength]);
         char _pNamedPipeName[MaxNamedPipeNameLength]; // https://docs.microsoft.com/en-us/windows/desktop/api/winbase/nf-winbase-createnamedpipea
+
+        DiagnosticsIpc(const char(&namedPipeName)[MaxNamedPipeNameLength]);
 #endif /* FEATURE_PAL */
 
         DiagnosticsIpc() = delete;