ABI of gcc?

junkoi · Post by **junkoi** » Thu Apr 10, 2008 11:36 pm

Hi,

Anybody knows where to get the ABI of gcc? I want to know which registers (x86) are reserved and clobbered when calling a C function.

Thanks,
J

2xpc · Post by **2xpc** » Fri Apr 11, 2008 12:45 am

Hi Junkoi,

Maybe the following url will help you. : http://www.delorie.com/djgpp/doc/ug/asm/calling.html

Basically just push eax, ecx, and edx to save them, then push the function's arguments on the stack then 'call' the C function . GCC does NOT pop the function's arguments, it's up to you to pop them after the call.
2xpc.

JamesM · Post by **JamesM** » Fri Apr 11, 2008 1:20 am

GCC implements this abi: registers $s0-$s7, $ra, $at are stored on the stack, all others are scratch... oh wait you were talking about the cdecl ABI. That GCC happens to implement.

2xpc · Post by **2xpc** » Fri Apr 11, 2008 3:24 am

Ok I admit I assumed Junkoi wants to call some C function from assembly

JamesM · Post by **JamesM** » Fri Apr 11, 2008 3:25 am

2xpc wrote:Ok I admit I assumed Junkoi wants to call some C function from assembly

... from 32 bit x86 only.