masm example

[Gunther]

Does the masm32 package contain an example for a procedure which is callable from C (VC, gcc or whatever Windows C compiler)? I haven't found nothing.

Gunther

[dedndave]

i seem to recall a thread in the old forum about "c-callable" routines

[qWord]

That is very simple if you use PROC/ENDP

Code Select Expand

include \masm32\include\masm32rt.inc
.code
; double foo(double x); // assuming __cdecl
foo proc c x:REAL8

fld x
fmul st,st
ret

foo endp
end
for the C program, add the corresponding *.obj file to the linker.
You may also take a look into Agner Fogs calling convention manual  to look up parameter passing and return values.

[Gunther]

Thank you qWord, that helped really.  :t

Gunther

[MichaelW]

A minimal-overhead (32-bit integer) compare procedure for the CRT qsort function:

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OPTION PROLOGUE:NONE
OPTION EPILOGUE:NONE

align 4
compare proc C p1:DWORD, p2:DWORD
    mov eax, [esp+4]
    mov edx, [esp+8]
    mov eax, [eax]
    mov edx, [edx]
    sub eax, edx
    ret
compare endp

OPTION PROLOGUE:PrologueDef
OPTION EPILOGUE:EpilogueDef


But at least for the Microsoft compilers there is no need to code the procedure in MASM, because you can create a naked function in C that has the same minimal overhead, and that can use exactly the same assembly code. I can't recall ever trying a naked function with GCC.

[Gunther]

Hi Michael,

But at least for the Microsoft compilers there is no need to code the procedure in MASM, because you can create a naked function in C that has the same minimal overhead, and that can use exactly the same assembly code. I can't recall ever trying a naked function with GCC.

thank you for providing the code. With gcc I've experimented with naked functions some years ago. It works, too. I will find the example code on one of my older machines. But your proposal shows the right direction.

Gunther

[Vortex]

Hi Gunther,

Here is a Pelles C example calling the StdOut function from masm32.lib :

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#include <stdio.h>

extern int __stdcall StdOut(char *);

int main(int argc,char *argv[])
{
StdOut("StdOut function called from masm32.lib\n");
return 0;
}

[Gunther]

Thank you for the example, Erol.  :t

Gunther

[goofprog]

These are cool.  Use a function pointer and assign it.