[Python-bugs-list] [ python-Bugs-471432 ] __cdecl / __stdcall unspecified in *.h

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Bugs item #471432, was opened at 2001-10-15 12:18
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Category: Windows
Group: Platform-specific
Status: Open
Resolution: None
Priority: 5
Submitted By: Frederic Giacometti (giacometti)
Assigned to: Mark Hammond (mhammond)
Summary: __cdecl / __stdcall unspecified in *.h

Initial Comment:

Currently, the win32 function call convention
(__stdcall vs __cdecl)  is never specified in the
function prototypes contained in the .h header files.

The call convention is therefore left up to the
configuration of the compiler incluing the header files
(__cdecl by default on VC++).

However, there are situations in which the compiler
default call convention must be set to __stdcall (/Gz
option on VC++'s cl.exe), and this makes the link fail;
until __cdecl keywords are manually insterted in the
Python.h function prototypes required for linking.

[For instance, /Gz is required when using typedef
definitions on function pointers, later passed as
arguments on __stdcall functions (the default on
Microsoft/commercial libraries)].

Besides, Microsoft recommands, it the VC++
documentation,  that the __stdcall convention be used
by default for function with fixed numbers of arguments
(smaller code size and better performances); __cdecl
being limited for use with functions with variable
number of args ('...').

A solution would consist in defining:
#ifdef _MS_VER
#define FIXARGCALL __stdcall
#define VARARGCALL __cdecl
#else
...
#endif

and sticking FIXARGCALL / VARARGCALL in front of all
DLL_IMPORT(), macro calls associated to a an exported
function prototype, across all Python .h files.

Frederic Giacometti


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>Comment By: Frederic Giacometti (giacometti)
Date: 2001-10-16 10:19

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The fault is not in the other libraries.

In MS Windows, 'well-behaved' libraries define explicitely
the calling conventions for each function in their header
file. This is all.

There's nobody's guts loosely hanging out in this ;).

FG

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Comment By: Tim Peters (tim_one)
Date: 2001-10-15 20:00

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I guess my first question is, if library X needs something 
other than the default, why isn't it X's responsibility to 
force *their* non-default behavior where needed?  After 
all, they're the oddballs.  Some days I get real tired of 
cleaing up after everyone else's loose bowels <0.9 wink>.

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Comment By: Mark Hammond (mhammond)
Date: 2001-10-15 18:45

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This does make sense to me, and I have even been bitten by 
it.

There are some strange libraries out there that need to be 
compiled with a different calling convention than the 
default.  Trying to extend Python with such a library can 
be difficult.  Having the calling convention specified in 
the prototypes would solve the problem.

I have never been brave enough to do it, given the small 
number of times it has been reported as a problem.  
However, I would be happy to help come up with a reasonable 
scheme.

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Comment By: Frederic Giacometti (giacometti)
Date: 2001-10-15 12:46

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As far as MS Windows / dll stuff is concerned, you're
already swimming in non-C-ANSI fishtank anyway (e.g.
DLL_IMPORT() macros...).
Just try to keep the right fishes in the tank :))

FG


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Comment By: Tim Peters (tim_one)
Date: 2001-10-15 12:34

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Mark, does this make sense to you?  Any notion that we 
*have* to add non-standard decorations seems inherently 
fishy to me.

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