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
The
reallocarray() 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
malloc(3),
realloc(3),
reallocarr(3)
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).