Subject: re: stdcall
From: [email-masked] (Mumit Khan)

6 Jan 1999 02:28:52 -0800
Message-ID: <[email-masked]>
References: <[email-masked]>
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To: [email-masked]
Cc: [email-masked]

On Mon, 4 Jan 1999 [email-masked] wrote:

> When writing a win32 application, how are STDCALL functions handled?
> If the windows API expects to pop arguments to a call, how does 
> egcs handle it?  Does it do the 'right' thing?  Is there an interface
> layer that does it?  Is this option available available on other
> platforms?

They're handled exactly as the GCC documentation suggests. Yes, it 
mostly does the right thing[1]. I'm not sure what you mean by an 
interface layer, but see [2] below. And, yes, it's supported under 
all platforms; why you'd want to use it on any other platform where 
you don't have to is of course an altogether different issue!

[1] There is nasty bug GCC code generation bug with STDCALL (aka WINAPI) 
routines that causes any function return floats or doubles to return
garbage. This is quite a low priority for GCC developers, so unless
someone contributes the fix, who knows when it'll get fixed.
Unfortunately, this particular bug makes it hard to use GCC to write DLLs
for VB, which requires WINAPI/STDCALL calling convention.

[2] GCC uses "attributes" to tag a function STDCALL/CDECL etc. See GCC
docs for more info. eg., the following function is going to use STDCALL
calling convention:
  
  int __attribute__((stdcall)) foo ();

Since writing the attributes are painful, and since we want to maintain
source level compatibility, GCC also predefines __stdcall to expand to the
above, and so you can instead write:

  int __stdcall foo ();

Or, you can use IMO the preferred style and use pre-defined macros WINAPI
and CDECL (found by including windows.h):
  
  int WINAPI foo ();

Regards,
Mumit

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