Re: [PATCH v4] Add reallocarray function.

[DJ Delorie <dj at redhat dot com>]

Dennis Wlfing <denniswoelfing@gmx.de> writes:
>>> diff --git a/malloc/reallocarray.c b/malloc/reallocarray.c
>>> +void *
>>> +__libc_reallocarray (void *optr, size_t nmemb, size_t elem_size)
>
> The header include/stdlib.h (not to be confused with stdlib/stdlib.h) is
> an internal glibc header. It declares the function prefixed with __libc_
> so that other glibc functions can call it without causing namespace
> problems. In the public headers only reallocarray is declared which is a
> weak alias for __libc_reallocarray.

I was mostly concerned with the __THROW differences.  I've seen those
cause problems in the past.

> The check_mul_overflow_size_t function was put in the new
> malloc-private.h header because malloc-internal.h is also used in other
> parts of glibc.

I have no problems with other parts of glibc seeing it, as long as it
has a suitable name.  I'm just trying to avoid having too many headers
without a good reason for them.

>>> +  /* Overflow should leave buffer untouched.  */
>> 
>> This requirement isn't documented anywhere...
>
> The reallocarray documentation says that reallocarray is equivalent to
> realloc(ptr, nmemb*size) and the realloc documentation says it does not
> modify the memory block on failure.

True, but overflow is a new condition that realloc doesn't have, that's
all, and since overflow checking is the *reason* for reallocarray, it
makes sense to clarify how it works.