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

David Abrahams dave at boost-consulting.com
Sat Jul 9 03:46:42 CEST 2005

"Martin v. Löwis" <martin at v.loewis.de> writes:

David Abrahams wrote:

If there is some library with such objects that happens to get wrapped and dynamically linked into a Python interpreter

Whoa there. How would that ever happen under ordinary circumstances? Doesn't Python's makefile control what gets linked to Python? Not entirely. By extending Modules/Setup

You mean http://cvs.sourceforge.net/viewcvs.py/python/python/dist/src/Modules/Setup.dist?view=markup ?

e.g. in the way freeze works), it is well possible to have additional extension modules linked into the Python interpreter, extension modules which are not part of the standard Python distribution.

In fact, before Python supported dynamic loading of extension modules, this was the only way to use non-standard extension modules. You always had to build your own version of the Python interpreter. I believe ccpython.cc dates back to these times.

That explains a lot.

I contend that either:

a. Anyone making that sort of extension with a C++ module should explicitly request --with-cxx, or

b. The python build system should automatically detect that --with-cxx is needed based on the presence of C++ extension modules.

Frankly I think b. would require an impractical amount of work and, speaking as an author of C++ extension modules, I don't think a. is much of a burden to impose.

If there's someone around here who is responsible for this change and knows its real rationale, can (s)he please tell me what it is? If not, can we please change things back so Python doesn't get linked to the C++ runtime by default? ccpython.cc and --with-cxx was first published in Python 1.6, and hasn't changed much since. So for some of you, it has "always" been there. It was contributed by Geoff Furnish. What has changed now is that the configure test suddenly determines that you need to link with g++ on Linux if main was compiled with g++. This was not the case before, but now is (since g++ 3.2 or something).

I see. Well, everything has become clear, thank you. My proposed remedy hasn't changed, though.

-- Dave Abrahams Boost Consulting www.boost-consulting.com

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