Re: [PATCH v2 7/7] hppa: Fix undefined behaviour in feclearexcept (BZ 30983)

[Carlos O'Donell <carlos@redhat.com>]

On 11/6/23 08:27, Adhemerval Zanella wrote:
> From: Bruno Haible <bruno@clisp.org>
> 
> The expression
> 
>   (excepts & FE_ALL_EXCEPT) << 27
> 
> produces a signed integer overflow when 'excepts' is specified as
> FE_INVALID (= 0x10), because
>   - excepts is of type 'int',
>   - FE_ALL_EXCEPT is of type 'int',
>   - thus (excepts & FE_ALL_EXCEPT) is (int) 0x10,
>   - 'int' is 32 bits wide.

Agreed.

> 
> The patched code produces the same instruction sequence as
> previosuly.

LGTM.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> ---
>  sysdeps/hppa/fpu/fclrexcpt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sysdeps/hppa/fpu/fclrexcpt.c b/sysdeps/hppa/fpu/fclrexcpt.c
> index 055fb04ccc..46caf39ec1 100644
> --- a/sysdeps/hppa/fpu/fclrexcpt.c
> +++ b/sysdeps/hppa/fpu/fclrexcpt.c
> @@ -26,7 +26,7 @@ feclearexcept (int excepts)
>    /* Get the current status word. */
>    __asm__ ("fstd %%fr0,0(%1)" : "=m" (s.l) : "r" (&s.l) : "%r0");
>    /* Clear all the relevant bits. */
> -  s.sw[0] &= ~((excepts & FE_ALL_EXCEPT) << 27);
> +  s.sw[0] &= ~(((unsigned int) excepts & FE_ALL_EXCEPT) << 27);
>    __asm__ ("fldd 0(%0),%%fr0" : : "r" (&s.l), "m" (s.l) : "%r0");
>  
>    /* Success.  */

-- 
Cheers,
Carlos.