Re: [Qemu-devel] [PULL for-2.5] tcg: Fix highwater check

[Stefan Weil]

Am 23.11.2015 um 13:45 schrieb Richard Henderson:
> From: John Clarke <address@hidden>
> 
> A simple typo in the variable to use when comparing vs the highwater mark.
> Reports are that qemu can in fact segfault occasionally due to this mistake.
> 
> Signed-off-by: John Clarke <address@hidden>
> Signed-off-by: Richard Henderson <address@hidden>
> ---
>  tcg/tcg.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tcg/tcg.c b/tcg/tcg.c
> index 682af8a..b20ed19 100644
> --- a/tcg/tcg.c
> +++ b/tcg/tcg.c
> @@ -2443,7 +2443,7 @@ int tcg_gen_code(TCGContext *s, tcg_insn_unit 
> *gen_code_buf)
>             one operation beginning below the high water mark cannot overrun
>             the buffer completely.  Thus we can test for overflow after
>             generating code without having to check during generation.  */
> -        if (unlikely(s->code_gen_ptr > s->code_gen_highwater)) {
> +        if (unlikely((void *)s->code_ptr > s->code_gen_highwater)) {
>              return -1;
>          }
>      }
> 

Is a comparison of void pointers portable? Or would it be better
to cast both sides to uintptr_t? Or fix the declaration of
code_gen_highwater to use an uint8_t pointer and cast s->code_ptr
to that type? code_gen_highwater should be fixed anyway because
in translate-all a difference is calculated with it.

Stefan