[Distutils] Does anyone understand what's going on with libpython on Linux?

Antoine Pitrou solipsis at pitrou.net
Sun Feb 7 07:38:56 EST 2016

On Sun, 7 Feb 2016 00:25:57 -0800
"Robert T. McGibbon" <rmcgibbo at gmail.com> wrote:
> > What are Debian/Ubuntu doing in distutils so that extensions don't link
> to libpython by default?
> I don't know exactly, but one way to reproduce this is simply to build the
> interpreter without `--enable-shared`.

See https://bugs.python.org/issue21536. It would be nice if you could
lobby for this issue to be resolved... (though that would only be for
3.6, presumably)

> I don't know that their reasons are, but I presume that the Debian
> maintainers have a well-considered reason for this design.

Actually, shared library builds can be noticeably slower. I did
measurements some time ago, and the results are:
- shared builds are 5-10% slower on x86
- they can be up to 30% slower on some ARM CPUs!
(this is on pystone which is a very crude benchmark, but in this case I
think the pattern is more general, since any function call internal to
Python is affected by the difference in code generation: shared library
builds add an indirection overhead when resolving non-static symbols)

Note btw. that Anaconda builds are also shared library builds.



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