Xref: news2.mv.net comp.os.msdos.djgpp:4833
From: terra AT diku DOT dk (Morten Welinder)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Inline ASM and variables
Date: 10 Jun 1996 16:22:15 GMT
Organization: Department of Computer Science, U of Copenhagen
Lines: 33
Sender: terra AT tyr DOT diku DOT dk
Message-ID: <4phi3n$ajc@vidar.diku.dk>
References: <31BB2931 DOT 3BB0 AT ix DOT netcom DOT com>
NNTP-Posting-Host: tyr.diku.dk
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

Brian Drum <drum AT ix DOT netcom DOT com> writes:

>For eaxample:

>void foo(int x) {
>  __asm__ __volatile__ ("
>    movl _x, %%eax"
>    :
>    :
>    :"eax" );
>}

>Won't work.  I get the following linker error:
>test_asm.c(.text+0x4): undefined reference to `x'

>I know that I could simply have GCC load x for me but that won't do in 
>the more complicated things that I'm doing because I don't want to use 
>up a bunch of registers.

Well, you _should_ make GCC do those things.  Your objection seems
to be based on an incorrect basis; if you use "m" (or "g") as
constraint you don't (necessarily) get the operand passed in
a register.  The worst problem with this method seems to be that
you can't have more than ten arguments.

Anyway, GCC handles asm (...) by shipping it out into the assembler
file.  It doesn't even attempt to grok symbols so only non-local
symbols can be accessed.

Perhaps if you post more about your problem you can get more
specific advice.

Morten