Issue #13590: On OS X 10.7 and 10.6 with Xcode 4.2, building
Distutils-based packages with C extension modules may fail because
Apple has removed gcc-4.2, the version used to build python.org
64-bit/32-bit Pythons. If the user does not explicitly override
the default C compiler by setting the CC environment variable,
Distutils will now attempt to compile extension modules with clang
if gcc-4.2 is required but not found. Also as a convenience, if
the user does explicitly set CC, substitute its value as the default
compiler in the Distutils LDSHARED configuration variable for OS X.
(Note, the python.org 32-bit-only Pythons use gcc-4.0 and the 10.4u
SDK, neither of which are available in Xcode 4. This change does not
attempt to override settings to support their use with Xcode 4.)
diff --git a/Lib/distutils/sysconfig.py b/Lib/distutils/sysconfig.py
index 0d6d4c4..4f9041a 100644
--- a/Lib/distutils/sysconfig.py
+++ b/Lib/distutils/sysconfig.py
@@ -141,6 +141,7 @@
"I don't know where Python installs its library "
"on platform '%s'" % os.name)
+_USE_CLANG = None
def customize_compiler(compiler):
"""Do any platform-specific customization of a CCompiler instance.
@@ -153,8 +154,38 @@
get_config_vars('CC', 'CXX', 'OPT', 'CFLAGS',
'CCSHARED', 'LDSHARED', 'SO')
+ newcc = None
if 'CC' in os.environ:
- cc = os.environ['CC']
+ newcc = os.environ['CC']
+ elif sys.platform == 'darwin' and cc == 'gcc-4.2':
+ # Issue #13590:
+ # Since Apple removed gcc-4.2 in Xcode 4.2, we can no
+ # longer assume it is available for extension module builds.
+ # If Python was built with gcc-4.2, check first to see if
+ # it is available on this system; if not, try to use clang
+ # instead unless the caller explicitly set CC.
+ global _USE_CLANG
+ if _USE_CLANG is None:
+ from distutils import log
+ from subprocess import Popen, PIPE
+ p = Popen("! type gcc-4.2 && type clang && exit 2",
+ shell=True, stdout=PIPE, stderr=PIPE)
+ p.wait()
+ if p.returncode == 2:
+ _USE_CLANG = True
+ log.warn("gcc-4.2 not found, using clang instead")
+ else:
+ _USE_CLANG = False
+ if _USE_CLANG:
+ newcc = 'clang'
+ if newcc:
+ # On OS X, if CC is overridden, use that as the default
+ # command for LDSHARED as well
+ if (sys.platform == 'darwin'
+ and 'LDSHARED' not in os.environ
+ and ldshared.startswith(cc)):
+ ldshared = newcc + ldshared[len(cc):]
+ cc = newcc
if 'CXX' in os.environ:
cxx = os.environ['CXX']
if 'LDSHARED' in os.environ: