[Python-Dev] Linux Python linking with G++? (original) (raw)

"Martin v. Löwis" martin at v.loewis.de
Fri Jul 8 07:31:41 CEST 2005

Jeff Epler wrote:

If we change the linker back to gcc, not g++, will it work if extension module 1 gets linked with libstdc++ A and ABI Q, and extension module 2 gets linked with libstdc++ B and ABI Z?

The problem is that it won't link at all. Compiling Modules/ccpython.o using g++ creates (in some installations) a reference to libgcc functions that won't be resolved unless you also link using g++. This is because libgcc was split into two libraries, and only one of them gets automatically linked when linking with gcc; the missing symbol is in the other library which only gets linked automatically when linking with g++.

What if a built-in module is written in C++, as it might be for some people embedding C++? (this will force use of g++ as the linker, right?)

Right. If those people also use dynamic extensions, they should make sure that those link against the same libstdc++.

PS The Python 2.3 and Python 2.4 binaries installed on my Fedora Core machine don't list libstdc++ in rpm -q --requires python' or ldd /usr/bin/python'. I don't see a patch that would change Python's behavior in the SRPM, though. I wonder what the difference is between my FC2 and the other systems...

One solution/work-around is to configure Python with --without-cxx. Then ccpython.cc won't be used, and all compiling and linking is done using gcc. Whether or not this would still allow for extension modules to use C++ depends on the platform; on Linux, it will.

I believe Linux distributors normally build Python with --without-cxx.

Regards, Martin

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