On Mon, 2005-06-06 at 19:26 -0400, Mike Frysinger wrote:
> i use asm label tricks:
> $ cat test.c
> int main(int argc, char *argv[])
> {
> int a;
> asm("startit:");
> a = 10;
> asm("stopit:");
> return 0;
> }
>
> $ gcc -c test.c && objdump -d test.o
> test.o: file format elf64-x86-64
>
> Disassembly of section .text:
>
> 0000000000000000 <main>:
> 0: 55 push %rbp
> 1: 48 89 e5 mov %rsp,%rbp
> 4: 89 7d fc mov %edi,0xfffffffffffffffc(%rbp)
> 7: 48 89 75 f0 mov %rsi,0xfffffffffffffff0(%rbp)
>
> 000000000000000b <startit>:
> b: c7 45 ec 0a 00 00 00 movl $0xa,0xffffffffffffffec(%rbp)
>
> 0000000000000012 <stopit>:
> 12: b8 00 00 00 00 mov $0x0,%eax
> 17: c9 leaveq
> 18: c3 retq
> -mike
Well, the pages I was reading used the nop trick but it looks like a
better solution has been presented. I almost forgot that integers are
still 32 bit on x86-64 so explaining the movl instead of movq. For
those interested the "gcc -S" is (the #APP/#NO_APP is gcc's way of
marking inline asm):
--------- 8< ----------
#APP
startit:
#NO_APP
movl $10, -20(%rbp)
#APP
stopit:
#NO_APP
--------- >8 ----------
Thanks Vapier,
--
Tres
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