Re: [Qemu-devel] [PATCH 1/2] target-i386: Use 1UL for bit shift

[Paolo Bonzini]

On 29/09/2015 22:34, Eduardo Habkost wrote:
> Fix undefined behavior detected by clang runtime check:
> 
>   qemu/target-i386/cpu.c:1494:15: runtime error:
>     left shift of 1 by 31 places cannot be represented in type 'int'
> 
> While doing that, add extra parenthesis for clarity.
> 
> Reported-by: Peter Maydell <address@hidden>
> Signed-off-by: Eduardo Habkost <address@hidden>
> ---
>  target-i386/cpu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 2b914b2..6af6db9 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -1491,7 +1491,7 @@ static void report_unavailable_features(FeatureWord w, 
> uint32_t mask)
>      int i;
>  
>      for (i = 0; i < 32; ++i) {
> -        if (1 << i & mask) {
> +        if ((1UL << i) & mask) {

1U is enough.

Paolo

ps: Ego ceterum censeo that these warnings are useless and uglify the
code unnecessarily.  But it looks like I'm in a minority so the patch is
okay.

>              const char *reg = get_register_name_32(f->cpuid_reg);
>              assert(reg);
>              fprintf(stderr, "warning: %s doesn't support requested feature: "
>