nasm/yasm arguments, linkage to C++
- by arionik
Hello everybody,
I've got a question concerning nasm and its linkage to C++. I declare a litte test function as
extern "C" void __cdecl myTest( byte i1, byte i2, int stride, int *width );
and I call it like this:
byte i1 = 1, i2 = 2;
int stride = 3, width = 4;
myTest( i1, i2, stride, &width );
the method only serves to debug assembly and have a look at how the stack pointer is used to get the arguments. beyond that, the pointer arguments value shall be set to 7, to figure out how that works. This is implemented like this:
global _myTest
_myTest:
mov eax, [esp+4] ; 1
mov ebx, [esp+8] ; 2
mov ecx, dword [esp+16] ; width
mov edx, dword [esp+12] ; stride
mov eax, dword [esp+16]
mov dword [eax], 7
ret
and compiled via
yasm -f win32 -g cv8 -m x86 -o "$(IntDir)\$(InputName).obj" "$(InputPath)"
, then linked to the c++ app. In debug mode, everything works fine. the function is called a couple of times and works as expected, whereas in release mode the function works once, but subsequent programm operations fail. It seems to me that something's wrong with stack/frame pointers, near/far, but I'm quite new to this subject and need a little help. thanks in advance!
a.
