[Python-Dev] Linux Python linking with G++?

["Martin v. Löwis"]

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