Lennyk <lennyk430@xxxxxxxxx> writes:
> Code (Window-style):
> int bswap(int n)
> {
> __asm
> {
> mov eax, n
> bswap eax
> mov n, eax
> }
> return n;
> }
>
> After looking at some guides/tutorials I've translated this code to Linux:
> int bswap(int n)
> {
> asm(".intel_syntax noprefix");
> asm("mov eax, n");
> asm("bswap eax");
> asm("mov n, eax");
> asm(".att_syntax noprefix");
> return n;
> }
>
> Compilation passes - but the linker shouts: "undefined reference to `n'"
>
> What am I doing wrong? Shouldn't it be straight forward to translate
> these simple commands to Linux?
gcc inline assembler does not work like that. You can't simply refer to
local variables in the assembler code. I recommend the friendly manual:
http://gcc.gnu.org/onlinedocs/gcc-4.4.0/gcc/Extended-Asm.html
In this case, though, you shouldn't use inline assembler at all, just
use __builtin_bswap32.
http://gcc.gnu.org/onlinedocs/gcc-4.4.0/gcc/Other-Builtins.html
Ian
