check non-existent registers (abx)

[ClaudioDaffra]

when i enter this assembly code :

add eax , byte ptr [abx+edi*2]

assember generates the following code

Assembly Raw Hex (zero bytes in bold):

02047D00000000

String Literal:

"\x02\x04\x7D\x00\x00\x00\x00"

Array Literal:

{ 0x02, 0x04, 0x7D, 0x00, 0x00, 0x00, 0x00 }

Disassembly: 0: 02 04 7d 00 00 00 00 add al,BYTE PTR [edi*2+0x0]

[defuse]

That's.... really interesting! Under the hood it's just passing it on to GCC so I doubt I can fix it. My guess at what's happening is it thinks abx as a variable or macro or something and evaluates to 0. Or you might've found a bug in the gcc assembler.

[ClaudioDaffra]

I have done some tests

gcc prova.c -o prova.exe -masm=intel

but compiler gives me right error message :

C:\Users\DAFFRA~1\AppData\Local\Temp\cc8IvaME.o:prova.c:(.text+0x1d): 
    undefined reference to `abx'
collect2.exe: error: ld returned 1 exit status

gcc version 4.9.2 (i686-posix-sjlj, built by strawberryperl.com project)

#include <stdio.h>

int main ( void ) 
{
    int src = 1;
    int dst;   

    asm ("add al , byte ptr [abx+edi*2]\n\t"
    : "=r" (dst) 
    : "r" (src)
    );

    printf("%d\n", dst);

 return 0 ;
}