[C++-sig] [Python-Dev] GCC version compatibility

Christoph Ludwig cludwig at cdc.informatik.tu-darmstadt.de
Sun Jul 10 16:49:47 CEST 2005

On Sun, Jul 10, 2005 at 09:35:33AM -0400, David Abrahams wrote:
> Christoph Ludwig <cludwig at cdc.informatik.tu-darmstadt.de> writes:
> > I do not claim the 2 TUs test will cover all possible scenarios. I am not even
> > sure this decision should be left to an automated test. Because if the test
> > breaks for some reason then the user is left with a linker error that is
> > time-consuming to track down.
> However, at least by the usual hierarchy of values, the sort of
> runtime error that results from the current needless linking with C++
> on ELF/Linux is even worse.

Yes, but on ELF/Linux the default configuration should be --without-cxx
in the first place. If the build instructions make it sufficiently clear that
you should prefer this configuration whenever possible then this should be a
non-issue on platforms like ELF/Linux.

We learned that there are indeed platforms that require --with-cxx. There is
not much we can do for user on platforms that that also require the final
executable to be linked with the C++ compiler. They have to live with the
dependency on the C++ runtime and the likely runtime errors if the import
extension modules built with a different C++ compiler.

What about the platforms that require compilation of main() with a C++
compiler but allow you to link with the C compiler - can you import a C++
extension module built with C++ compiler version X if the main() function of
the Python interpreter was compiled with C++ compiler version Y, X != Y?
If not, then we are back to the runtime error, no matter whether there is a
dependency on the C++ runtime library or not.

So the automated test in configure could spare users runtime errors if they
must configure --with-cxx and if they can link with the C compiler and if the
C++ compiler versions used for building the Python interpreter and the
extension module do not need to coincide. I don't know how large the subset of
platforms is that satisfy these conditions.


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