Mail Archives: cygwin/1998/05/29/01:28:40
On 27-May-1998, Tim Newsham <newsham AT lava DOT net> wrote:
>
> I have a program which is trying to load a dll at runtime. The
> program uses LoadLibraryEx to load the library in, then uses GetProcAddress
> to get addresses of various entry points (with appropriate cast operations).
> This much seems to work properly. I am having problems, however, when
> I try to actually call one of the procedures. The stack pointer (esp)
> seems to be incorrect after a call to the procedure. In particular
> I am passing in 3 4-byte arguments (12 bytes). The emitted code
> looks like:
>
> <push args>
> call *%ebx
> addl %0xc, %esp
>
> After the call, the stack pointer seems to be off by 12 bytes (too high).
> Its as if the called procedure popped the arguments itself, leaving
> the stack as it was prior to the caller pushing, and then the caller
> also added 12 to the stack pointer to pop the values, after the function
> returned.
>
> Is this analysis correct?
Yes, it looks like the called procedure is using the "stdcall"
calling convention rather than the default "cdecl" calling convention.
> If so, is there some way to tell the compiler that the callee will be
> restoring the stack and that the caller shouldn't bother?
Yes, use `__attribute__((stdcall))' on the declaration of
the function pointer which you use to call the function.
See the "function attributes" section in the "C extensions"
section of the gcc documentation.
--
Fergus Henderson <fjh AT cs DOT mu DOT oz DOT au> | "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh> | of excellence is a lethal habit"
PGP: finger fjh AT 128 DOT 250 DOT 37 DOT 3 | -- the last words of T. S. Garp.
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