Merge pull request #145 from lopsided98/python-inc-cross

Fix finding headers when cross compiling

distutils/sysconfig.py

@@ -118,40 +118,74 @@ def get_python_inc(plat_specific=0, prefix=None):
     If 'prefix' is supplied, use it instead of sys.base_prefix or
     sys.base_exec_prefix -- i.e., ignore 'plat_specific'.
     """
-    if prefix is None:
-        prefix = plat_specific and BASE_EXEC_PREFIX or BASE_PREFIX
-    if os.name == "posix":
-        if IS_PYPY and sys.version_info < (3, 8):
-            return os.path.join(prefix, 'include')
-        if python_build:
-            # Assume the executable is in the build directory.  The
-            # pyconfig.h file should be in the same directory.  Since
-            # the build directory may not be the source directory, we
-            # must use "srcdir" from the makefile to find the "Include"
-            # directory.
-            if plat_specific:
-                return _sys_home or project_base
-            else:
-                incdir = os.path.join(get_config_var('srcdir'), 'Include')
-                return os.path.normpath(incdir)
-        implementation = 'pypy' if IS_PYPY else 'python'
-        python_dir = implementation + get_python_version() + build_flags
-        return os.path.join(prefix, "include", python_dir)
-    elif os.name == "nt":
-        if python_build:
-            # Include both the include and PC dir to ensure we can find
-            # pyconfig.h
-            return (
-                os.path.join(prefix, "include")
-                + os.path.pathsep
-                + os.path.join(prefix, "PC")
-            )
-        return os.path.join(prefix, "include")
-    else:
+    default_prefix = BASE_EXEC_PREFIX if plat_specific else BASE_PREFIX
+    resolved_prefix = prefix if prefix is not None else default_prefix
+    try:
+        getter = globals()[f'_get_python_inc_{os.name}']
+    except KeyError:
         raise DistutilsPlatformError(
             "I don't know where Python installs its C header files "
             "on platform '%s'" % os.name
         )
+    return getter(resolved_prefix, prefix, plat_specific)
+
+
+def _get_python_inc_posix(prefix, spec_prefix, plat_specific):
+    if IS_PYPY and sys.version_info < (3, 8):
+        return os.path.join(prefix, 'include')
+    return (
+        _get_python_inc_posix_python(plat_specific)
+        or _get_python_inc_from_config(plat_specific, spec_prefix)
+        or _get_python_inc_posix_prefix(prefix)
+    )
+
+
+def _get_python_inc_posix_python(plat_specific):
+    """
+    Assume the executable is in the build directory. The
+    pyconfig.h file should be in the same directory. Since
+    the build directory may not be the source directory,
+    use "srcdir" from the makefile to find the "Include"
+    directory.
+    """
+    if not python_build:
+        return
+    if plat_specific:
+        return _sys_home or project_base
+    incdir = os.path.join(get_config_var('srcdir'), 'Include')
+    return os.path.normpath(incdir)
+
+
+def _get_python_inc_from_config(plat_specific, spec_prefix):
+    """
+    If no prefix was explicitly specified, provide the include
+    directory from the config vars. Useful when
+    cross-compiling, since the config vars may come from
+    the host
+    platform Python installation, while the current Python
+    executable is from the build platform installation.
+    """
+    if not spec_prefix:
+        return
+    return get_config_var('CONF' * plat_specific + 'INCLUDEPY')
+
+
+def _get_python_inc_posix_prefix(prefix):
+    implementation = 'pypy' if IS_PYPY else 'python'
+    python_dir = implementation + get_python_version() + build_flags
+    return os.path.join(prefix, "include", python_dir)
+
+
+def _get_python_inc_nt(prefix, spec_prefix, plat_specific):
+    if python_build:
+        # Include both the include and PC dir to ensure we can find
+        # pyconfig.h
+        return (
+            os.path.join(prefix, "include")
+            + os.path.pathsep
+            + os.path.join(prefix, "PC")
+        )
+    return os.path.join(prefix, "include")
 
 
 # allow this behavior to be monkey-patched. Ref pypa/distutils#2.