Re: Problem with Object Size Checking and reallocarray

[Yaakov Selkowitz <yselkowitz at cygwin dot com>]

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?

-- 
Yaakov

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