Re: Problem with Object Size Checking and reallocarray

["Richard Earnshaw (lists)" <Richard dot Earnshaw at arm dot com>]

On 13/03/18 20:54, Yaakov Selkowitz wrote:
> On 2018-03-13 13:28, Richard Earnshaw (lists) wrote:
>> On 13/03/18 14:05, Yaakov Selkowitz wrote:
>>> On 2018-03-13 07:51, Corinna Vinschen wrote:
>>>> On Mar 12 19:58, Jon Turney wrote:
>>>>> reallocarray() is annotated in stdlib.h with '__alloc_size(2)
>>>>> __alloc_size(3)'
>>>>>
>>>>> per [1], this doesn't seem to be the correct syntax when the size is the
>>>>> product of the arguments, and the last alloc_size seems to be silently
>>>>> winning.
>>>>>
>>>>> If I change this to '__alloc_size((2,3))' (as in the patch attached),
>>>>> __builtin_object_size doesn't seem to be a compile-time constant anymore,
>>>>> and so memcpy() evaluates differently, so it's hard to be sure that's
>>>>> actually correct...
>>>>>
>>>>> [1] https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html
>>>>
>>>> Yaakov, care to comment and push if the patch is ok?
>>>
>>> Thanks, pushed.
>>>
>>
>> This doesn't work at all.  I get:
>>
>> warning: alloc_size parameter outside range [-Wattributes]
>>
>> There's too many levels of parenthesis around the parameters, so it
>> expands to
>> void *reallocarray(void *, size_t, size_t)
>> __attribute__((__alloc_size__((2,3))));
>>
>> And this causes all the testsuites to start failing due tot he warning.
>>
>> To silence the warning it needs to be __attribute__((__alloc_size__(2,3)))
>>
>> I'm not sure how you achieve that, given the macro expansion going on here.
> 
> Does the attached help?

Yes, that seems to fix it.

Thanks for the quick turn-around.

R.

> 
> 
> 0001-alloc-macros.patch
> 
> 
> diff --git a/newlib/libc/include/stdlib.h b/newlib/libc/include/stdlib.h
> index 593760a12..564ce8a28 100644
> --- a/newlib/libc/include/stdlib.h
> +++ b/newlib/libc/include/stdlib.h
> @@ -324,8 +324,8 @@ extern long double strtold (const char *__restrict, char **__restrict);
>   * If we're in a mode greater than C99, expose C11 functions.
>   */
>  #if __ISO_C_VISIBLE >= 2011
> -void *	aligned_alloc(size_t, size_t) __malloc_like __alloc_align(1)
> -	    __alloc_size(2);
> +void *	aligned_alloc(size_t, size_t) __malloc_like __alloc_align((1))
> +	    __alloc_size((2));
>  int	at_quick_exit(void (*)(void));
>  _Noreturn void
>  	quick_exit(int);
> diff --git a/newlib/libc/include/sys/cdefs.h b/newlib/libc/include/sys/cdefs.h
> index fc564a5c6..b3f8d1965 100644
> --- a/newlib/libc/include/sys/cdefs.h
> +++ b/newlib/libc/include/sys/cdefs.h
> @@ -258,12 +258,12 @@
>  #define	__section(x)	__attribute__((__section__(x)))
>  #endif
>  #if __GNUC_PREREQ__(4, 3) || __has_attribute(__alloc_size__)
> -#define	__alloc_size(x)	__attribute__((__alloc_size__(x)))
> +#define	__alloc_size(x)	__attribute__((__alloc_size__ x))
>  #else
>  #define	__alloc_size(x)
>  #endif
>  #if __GNUC_PREREQ__(4, 9) || __has_attribute(__alloc_align__)
> -#define	__alloc_align(x)	__attribute__((__alloc_align__(x)))
> +#define	__alloc_align(x)	__attribute__((__alloc_align__ x))
>  #else
>  #define	__alloc_align(x)
>  #endif
>