BLD: Add configuration to allow cross platform builds for iOS.

When building NumPy for iOS, you build on macOS, with compiler flags to target iOS or the iOS simulator. However, setup.py runs on macOS, so sys.platform == 'darwin', regardless of the platform being targetted.

distutils provides an environment variable - _PYTHON_HOST_PLATFORM - to indicate when you are building for a different platform. This patches uses that variable to identify cross-platform builds and disable macOS specific features.

The patch also renames an internal method in strfuncs to avoid a collision with a symbol in iOS's standard library, and includes math.h to avoid errors about undefined symbols.

4 files changed, 21 insertions, 10 deletions

diff --git a/numpy/_build_utils/apple_accelerate.py b/numpy/_build_utils/apple_accelerate.py
index 2d5bbab5e..36dd7584a 100644
--- a/numpy/_build_utils/apple_accelerate.py
+++ b/numpy/_build_utils/apple_accelerate.py
@@ -8,8 +8,13 @@ __all__ = ['uses_accelerate_framework', 'get_sgemv_fix']
 
 def uses_accelerate_framework(info):
     """ Returns True if Accelerate framework is used for BLAS/LAPACK """
+    # If we're not building on Darwin (macOS), don't use Accelerate
     if sys.platform != "darwin":
         return False
+    # If we're building on macOS, but targeting a different platform,
+    # don't use Accelerate.
+    if os.getenv('_PYTHON_HOST_PLATFORM', None):
+        return False
     r_accelerate = re.compile("Accelerate")
     extra_link_args = info.get('extra_link_args', '')
     for arg in extra_link_args:
diff --git a/numpy/core/src/multiarray/strfuncs.c b/numpy/core/src/multiarray/strfuncs.c
index 646d15cdb..495d897b2 100644
--- a/numpy/core/src/multiarray/strfuncs.c
+++ b/numpy/core/src/multiarray/strfuncs.c
@@ -41,7 +41,7 @@ PyArray_SetStringFunction(PyObject *op, int repr)
  * XXX we do this in multiple places; time for a string library?
  */
 static char *
-extend(char **strp, Py_ssize_t n, Py_ssize_t *maxp)
+extend_str(char **strp, Py_ssize_t n, Py_ssize_t *maxp)
 {
     char *str = *strp;
     Py_ssize_t new_cap;
@@ -71,7 +71,7 @@ dump_data(char **string, Py_ssize_t *n, Py_ssize_t *max_n, char *data, int nd,
     npy_intp i, N, ret = 0;
 
 #define CHECK_MEMORY do {                           \
-        if (extend(string, *n, max_n) == NULL) {    \
+        if (extend_str(string, *n, max_n) == NULL) {    \
             ret = -1;                               \
             goto end;                               \
         }                                           \
diff --git a/numpy/distutils/system_info.py b/numpy/distutils/system_info.py
index 5bda213e7..d12381028 100644
--- a/numpy/distutils/system_info.py
+++ b/numpy/distutils/system_info.py
@@ -219,21 +219,21 @@ if sys.platform == 'win32':
     _lib_dirs = [
         'lib',
     ]
-    
+
     _include_dirs = [d.replace('/', os.sep) for d in _include_dirs]
     _lib_dirs = [d.replace('/', os.sep) for d in _lib_dirs]
     def add_system_root(library_root):
         """Add a package manager root to the include directories"""
         global default_lib_dirs
         global default_include_dirs
-        
+
         library_root = os.path.normpath(library_root)
- 
+
         default_lib_dirs.extend(
             os.path.join(library_root, d) for d in _lib_dirs)
         default_include_dirs.extend(
             os.path.join(library_root, d) for d in _include_dirs)
-    
+
     if sys.version_info >= (3, 3):
         # VCpkg is the de-facto package manager on windows for C/C++
         # libraries. If it is on the PATH, then we append its paths here.
@@ -247,7 +247,7 @@ if sys.platform == 'win32':
             else:
                 specifier = 'x64'
 
-            vcpkg_installed = os.path.join(vcpkg_dir, 'installed') 
+            vcpkg_installed = os.path.join(vcpkg_dir, 'installed')
             for vcpkg_root in [
                 os.path.join(vcpkg_installed, specifier + '-windows'),
                 os.path.join(vcpkg_installed, specifier + '-windows-static'),
@@ -260,7 +260,7 @@ if sys.platform == 'win32':
             conda_dir = os.path.dirname(conda)
             add_system_root(os.path.join(conda_dir, '..', 'Library'))
             add_system_root(os.path.join(conda_dir, 'Library'))
-                        
+
 else:
     default_lib_dirs = libpaths(['/usr/local/lib', '/opt/lib', '/usr/lib',
                                  '/opt/local/lib', '/sw/lib'], platform_bits)
@@ -1551,7 +1551,9 @@ class lapack_opt_info(system_info):
         if not atlas_info:
             atlas_info = get_info('atlas')
 
-        if sys.platform == 'darwin' and not (atlas_info or openblas_info or
+        if sys.platform == 'darwin' \
+                and not os.getenv('_PYTHON_HOST_PLATFORM', None) \
+                and not (atlas_info or openblas_info or
                                              lapack_mkl_info):
             # Use the system lapack from Accelerate or vecLib under OSX
             args = []
@@ -1657,7 +1659,9 @@ class blas_opt_info(system_info):
         if not atlas_info:
             atlas_info = get_info('atlas_blas')
 
-        if sys.platform == 'darwin' and not (atlas_info or openblas_info or
+        if sys.platform == 'darwin' \
+                and not os.getenv('_PYTHON_HOST_PLATFORM', None) \
+                and not (atlas_info or openblas_info or
                                              blas_mkl_info or blis_info):
             # Use the system BLAS from Accelerate or vecLib under OSX
             args = []
diff --git a/numpy/linalg/lapack_lite/f2c.h b/numpy/linalg/lapack_lite/f2c.h
index f5b90cd67..80f1a12b1 100644
--- a/numpy/linalg/lapack_lite/f2c.h
+++ b/numpy/linalg/lapack_lite/f2c.h
@@ -7,6 +7,8 @@
 #ifndef F2C_INCLUDE
 #define F2C_INCLUDE
 
+#include <math.h>
+
 typedef int integer;
 typedef char *address;
 typedef short int shortint;