Re: [RFC][PATCH] Add reallocarray function.

[Florian Weimer <fweimer@redhat.com>]

On 05/18/2014 10:32 PM, Rüdiger Sonderfeld wrote:
> +/* Re-allocate the previously allocated block in PTR, making the new
> +   block large enough for NMEMB elements of SIZE bytes each.  */
> +/* __attribute_malloc__ is not used, because if realloc returns
> +   the same pointer that was passed to it, aliasing needs to be allowed
> +   between objects pointed by the old and new pointers.  */
> +extern void *reallocarray (void *__ptr, size_t __nmemb, size_t __size)
> +     __THROW __attribute_warn_unused_result__;

I'm not sure if this is still on the table, but experience shows that 
the realloc interface is error-prone for another reason: The straight 
way to write an a reallocation,

   ptr = realloc(ptr, new_size);

leads to a memory leak on error.  It would be less error-prone to have 
reallocarray to update the pointer directly on success, e.g.:

   if (reallocarray(&ptr, new_count, sizeof(T)) < 0) {
     // handle error
   }

However, this cannot be implemented as a C function, only as a macro.
-- 
Florian Weimer / Red Hat Product Security