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REALLOCARRAY(3)            Library Functions Manual            REALLOCARRAY(3)

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).

NetBSD 8.0                     February 5, 2015                     NetBSD 8.0