[Python-bugs-list] [ python-Bugs-558488 ] DL_EXPORT on VC7 broken

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Bugs item #558488, was opened at 2002-05-20 19:18
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Category: Build
Group: Platform-specific
Status: Open
Resolution: None
Priority: 5
Submitted By: David Aldridge (daldridge)
Assigned to: Nobody/Anonymous (nobody)
>Summary: DL_EXPORT on VC7 broken

Initial Comment:
Extension modules (_sre, _socket, etc.) do not have 
their entry points exported correctly when building 
Python (2.1 onwards) with Microsoft Visual C++ 7 
(part of Visual Studio .NET).  (NOTE: Everything 
compiles and links without errors.  It's just the 
exports that are missing.)

Think through the prepocessor flow when compiling 
_sre.c, for example, the following happens (this is 
from memory so please excuse inaccuracies):

1) _sre.c #includes "python.h"

2) "python.h" pretty much immediatly 
#includes "config.h"

3) "config.h" has the following:

#ifdef USE_DL_IMPORT
#define DL_IMPORT(RTYPE) __declspec(dllimport) RTYPE
#endif
#ifdef USE_DL_EXPORT
#define DL_IMPORT(RTYPE) __declspec(dllexport) RTYPE
#define DL_EXPORT(RTYPE) __declspec(dllexport) RTYPE
#endif

4) USE_DL_EXPORT is NOT defined (and cannot be in the 
_sre project, or it will not import pythoncore's (?) 
exports), thus DL_EXPORT is not yet defined.

5) After preprocessing "config.h", we're back 
in "python.h", which has a block:

#ifndef DL_EXPORT
#define DL_EXPORT(RTYPE) RTYPE
#endif

6) Back in _sre.c, the extension module entry point 
is:

DL_EXPORT(void) init_sre()

This expands to

void init_sre()

And thus does not get exported.



If I change the "config.h" block above to be:

#ifdef USE_DL_IMPORT
#define DL_IMPORT(RTYPE) __declspec(dllimport) RTYPE
#define DL_EXPORT(RTYPE) __declspec(dllexport) RTYPE
#endif
#ifdef USE_DL_EXPORT
#define DL_IMPORT(RTYPE) __declspec(dllexport) RTYPE
#define DL_EXPORT(RTYPE) __declspec(dllexport) RTYPE
#endif

(ie. add the DL_EXPORT line if/when USE_DL_IMPORT is 
defined), everything works correctly.  Not 
guaranteeing this is the "correct" solution, but it 
seems to work.

My specific test case was to build everything, run 
python.exe from the command line, then 
attempt "import re".

This results in a Traceback with "ImportError: 
dynamic module does not define init function 
(init_sre)".


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