Re: [Qemu-devel] Redundant repz prefixes in generated amd64 code

[Johannes Schindelin]

Hi,

On Sat, 17 Mar 2007, axel wrote:

> Why there exist two different blocks for COFF and ELF for x86/x86_64 
> hosts?

Because COFF is used by Windows, and ELF by Linux, and they are 
substantially different?

> @@ -1458,6 +1458,8 @@
>              error("empty code for %s", name);
>          if (p_end[-1] == 0xc3) {
>              len--;
> +           if ( len>0 && p_end[-2] == 0xf3 )
> +               --len;

This is wrong in several accounts:

- style (space after opening parentheses and before closing parentheses, 
  no space before and after ">", "--" before instead of after "len", just 
  see the if clause above)

- if you want to access "p_end[-2]", you must check for "len > 1"

- you most likely want to check "p_end[-1]" anyway

- worst: there is no appropriate explanation why this patch is needed, and 
  even more importantly, why it does not break existing code

Hth,
Dscho