[New-bugs-announce] [issue6672] Add Mingw recognition to pyport.h to allow building extensions

[Jan Schlüter]

New submission from Jan Schlüter <python-bugs at jan-schlueter.de>:

This addresses missing statements for recognizing the Mingw compiler in 
pyport.h, needed to build several extension modules on Windows using 
Mingw. I will first explain the background, then indicate what needs to 
be changed and end with some pointers to "related work".

Pyport.h of Python 2.5 and 2.6 (I do not have other versions to check) 
addresses an issue with Cygwin's gcc by preventing the declaration of 
"__declspec(dllimport)" for function definitions (using the PyAPI_FUNC
(RTYPE) makro), relying on the compiler's auto-import definition 
instead, because the compiler would not otherwise throw an "initializer 
element is not constant" error when using e.g. PyObject_GenericGetAttr 
in a PyTypeObject declaration of a C/C++ extension module (more 
generally, whenever an imported Python API function is used as a 
constant).
Python 2.6.2 (r262:71605) and Python 2.5.4 (r254:67916) do not check 
for the Mingw compiler in pyport.h, although Mingw behaves the same as 
the Cygwin version, at least regarding the "__declspec" declaration.

To fix that, each check for __CYGWIN__ in pyport.h should also check 
for __MINGW32___ to behave the same way. svn.python.org currently does 
not reply, so I can not create a patch against the trunk nor check 
whether this issue has already been addressed.

Issue 5046 included a patch to pyport.h fixing this, but it has been 
rejected due to other suggested changes that were not mature.
http://recipes.gobolinux.org/r/?list=Python&ver=3.1-
r1&file=arm/20061116160247-
bf48b-7db78fe2f80b3137ce349cf4314364768555ff50.gz.diff suggests the 
same change.
http://www.indashpc.org/vbullettin/viewtopic.php?p=5003#5003 gives some 
more background information on how I found and fixed the problem.
An internet search for "python initializer element is not constant" 
shows that numerous people have been encountering this problem when 
trying to build a python extension module.

----------
components: Build
messages: 91427
nosy: f0k
severity: normal
status: open
title: Add Mingw recognition to pyport.h to allow building extensions
versions: Python 2.5, Python 2.6

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<http://bugs.python.org/issue6672>
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