Re: [PATCH] Use [[gnu::access(none)]] on free(3)

[Alejandro Colomar <alx@kernel.org>]

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On Fri, Jan 26, 2024 at 07:39:06PM +0100, Alejandro Colomar wrote:
> The lifetime of the object expires right at the boundary of the call to
> free(3), and the function doesn't access (neither read nor write) it, as
> far as the abstract machine is concerned.
> 
> Cc: Arsen Arsenović <arsen@gentoo.org>
> Cc: Andreas Schwab <schwab@linux-m68k.org>
> Cc: Xi Ruoyao <xry111@xry111.site>
> Cc: Russ Allbery <eagle@eyrie.org>
> Signed-off-by: Alejandro Colomar <alx@kernel.org>

Please do not apply.  Xi pointed out that GCC uses some magic that would
break with the attribute.

> ---
>  stdlib/stdlib.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/stdlib/stdlib.h b/stdlib/stdlib.h
> index 414c49d731..8dfd373bf5 100644
> --- a/stdlib/stdlib.h
> +++ b/stdlib/stdlib.h
> @@ -684,7 +684,8 @@ extern void *realloc (void *__ptr, size_t __size)
>       __THROW __attribute_warn_unused_result__ __attribute_alloc_size__ ((2));
>  
>  /* Free a block allocated by `malloc', `realloc' or `calloc'.  */
> -extern void free (void *__ptr) __THROW;
> +extern void free (void *__ptr)
> +     __THROW __attr_access ((__none__, 1));
>  
>  #ifdef __USE_MISC
>  /* Re-allocate the previously allocated block in PTR, making the new
> -- 
> 2.43.0
> 



-- 
<https://www.alejandro-colomar.es/>
Looking for a remote C programming job at the moment.

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