Date: Fri, 22 Apr 94 11:16:40 -0400
From: dj AT ctron DOT com (DJ Delorie)
To: dwang AT ee DOT WPI DOT EDU
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu

> I have a very simple problem but I can't figure out so far. That's about
> the combination of in-line assembly language within C programs under GCC 2.5.7.
> An example is as follows, that's in i386 version:
>         asm("movb data,%ax");
> here "data" is previously used in C routine. The GCC compiler told me that
> "undefined reference to 'data'". In fact, however, 'data' was defined in C 
> routine.

Try asm("movb _data,%ax").

A better solution is asm("movl %1,%%eax" : "r" (data));

Note that "movb" and "%ax" are incombatible.  "movb" is for bytes and
"%ax" is a 16-bit word.