[PATCH] add support for -Wmismatched-dealloc

[Florian Weimer]

* Martin Sebor via Libc-alpha:

> diff --git a/stdlib/stdlib.h b/stdlib/stdlib.h
> index 6360845d98..a555fb9c0f 100644
> --- a/stdlib/stdlib.h
> +++ b/stdlib/stdlib.h
> @@ -550,6 +550,9 @@ extern void *calloc (size_t __nmemb, size_t __size)
>  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;
> +
>  #ifdef __USE_MISC
>  /* Re-allocate the previously allocated block in PTR, making the new
>     block large enough for NMEMB elements of SIZE bytes each.  */
> @@ -558,11 +561,13 @@ extern void *realloc (void *__ptr, size_t __size)
>     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__
> -     __attribute_alloc_size__ ((2, 3));
> -#endif
> +     __attribute_alloc_size__ ((2, 3))
> +    __attr_dealloc_free;
>  
> -/* Free a block allocated by `malloc', `realloc' or `calloc'.  */
> -extern void free (void *__ptr) __THROW;
> +/* Add reallocarray as its own deallocator.  */
> +extern void *reallocarray (void *__ptr, size_t __nmemb, size_t __size)
> +     __attr_dealloc (reallocarray, 1);
> +#endif

This causes:

In file included from ../include/stdlib.h:15,
                 from ../test-skeleton.c:36,
                 from test-math-iszero.cc:164:
../stdlib/stdlib.h:568:14: error: declaration of ‘void* reallocarray(void*, size_t, size_t)’ has a different exception specifier
  568 | extern void *reallocarray (void *__ptr, size_t __nmemb, size_t __size)
      |              ^~~~~~~~~~~~
../stdlib/stdlib.h:562:14: note: from previous declaration ‘void* reallocarray(void*, size_t, size_t) noexcept’
  562 | extern void *reallocarray (void *__ptr, size_t __nmemb, size_t __size)
      |              ^~~~~~~~~~~~

Thanks,
Florian
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