reallocarray(3) - NetBSD Manual Pages

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REALLOCARRAY(3)         NetBSD 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 appro-
     priate 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 compati-
     bility reasons it's available since NetBSD 8 in the _OPENBSD_SOURCE
     namespace.


CAVEATS

     The reallocarray() function was designed to facilitate safe, robust pro-
     gramming 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 alloca-
     tion 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 9.1                     February 5, 2015                     NetBSD 9.1