NAME
reallocarray —
reallocate memory for an array of
elements checking for overflow
SYNOPSIS
#define _OPENBSD_SOURCE
#include
<stdlib.h>
void *
reallocarray(void *ptr,
size_t nmemb, size_t size);
DESCRIPTION
Thereallocarray()
function reallocates the pointer ptr to a size
appropriate to handle an allocation of nmemb elements in
an array where each of the array elements is size bytes
using realloc(3) and making sure that overflow does not happen in the
multiplication of “nmemb * size”.
This function is provided for source compatibility with OpenBSD and its use is discouraged in preference to reallocarr(3).
RETURN VALUES
The reallocarray() function will return
NULL if there was overflow or if
realloc(3) failed setting errno to
EOVERFLOW or preserving the value from
realloc(3).
SEE ALSO
STANDARDS
reallocarray() is an
OpenBSD extension.
HISTORY
The reallocarray() function first appeared
in OpenBSD 5.6.
reallocarray() was redesigned in
NetBSD 8 as
reallocarr(3). For
compatibility reasons it's available since NetBSD 8
in the _OPENBSD_SOURCE namespace.
CAVEATS
The reallocarray() function was designed
to facilitate safe, robust programming and overcome the shortcomings of the
malloc(3) and
realloc(3) functions by centralizing the overflow check in the
multiplication of nmemb and
size.
There are still portability issues (it does not solve the
0 sized allocation return ambiguity in the C
standard: does reallocarray() return
NULL or a unique pointer to memory that cannot be
accessed? Does a NULL mean that an error occurred,
and can someone check errno in that case to find out
what happened?).
For this reason NetBSD decided to go with an alternative implementation, and created reallocarr(3).