Ned Deily <n...@acm.org> added the comment:
When building and installing C extension modules, distutils attempts to use the
same compiler and some compiler options as Python itself was built with. For
the current (3.2.2 and 2.7.2) 64-bit/32-bit python installers, the standard
Apple-supplied gcc-4.2 in Xcode 3.2.x on OS X 10.6 was used. As of Xcode 4.2,
now standard for OS X 10.7 and optional for OS X 10.6, Apple no longer ships
gcc-4.2 in Xcode, in favor of clang and the transitional llvm-gcc. Moving the
entire Python build to another compiler is a major undertaking, requiring
careful testing, which is underway. A compiler change may well be deemed too
risky for a bug-fix release.
In any case, we can no longer assume that the same build compiler will be
available on most user systems. While it is possible for the user to manually
override the distutils defaults by setting the CC and LDSHARED environment
variables properly, setting the latter is tedious. For example, to manually
override to clang, the following is currently needed:
CC=clang
LDSHARED='clang -bundle -undefined dynamic_lookup \
-arch i386 -arch x86_64 -isysroot /Developer/SDKs/MacOSX10.6.sdk -g'
python setup.py ...
Attached is a patch that attempts to "do the right thing" for OS X. First, if
the default build compiler is gcc-4.2 and the compiler has not been explicitly
overridden by defining CC, distutils will check for the presence of gcc-4.2 on
the default path. If gcc-4.2 is not found and if clang is found, it will
automatically substitute clang as the build compiler. Second, if CC is used to
override the compiler selection but LDSHARED is not defined, distutils will
substitute the CC value into the default LDSHARED value. This allows simple
one-line compiler overrides, like:
CC=llvm-gcc python setup.py ...
To minimize the risk of unintended side effects, these changes would apply to
OS X only.
I propose applying this patch to 3.2 (for 3.2.3) and 2.7 (for 2.7.3) as well as
provisionally to default for 3.3; a second patch will be needed with similar
changes to packaging. After the evaluation of compiler alternatives is
complete and we decide what to do for 3.3, this approach might change.
----------
keywords: +patch
stage: -> patch review
Added file: http://bugs.python.org/file24442/issue13590_distutils.patch
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