reallocarray (3)

Leading comments

 Copyright (c) 1980, 1991, 1993
	The Regents of the University of California.  All rights reserved.

 This code is derived from software contributed to Berkeley by
 the American National Standards Committee X3, on Information
 Processing Systems.

 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions
 are met:
 1. Redistributions of source code must retain the above copyright
    notice, this list of conditions ...

(The comments found at the beginning of the groff file "man3/reallocarray.3bsd".)

NAME

reallocarray - memory allocation and deallocation

LIBRARY

Lb libbsd

SYNOPSIS

In stdlib.h (See libbsd(7) for include usage.) Ft void * Fn reallocarray void *ptr size_t nmemb size_t size

DESCRIPTION

When using Fn malloc be careful to avoid the following idiom:

if ((p = malloc(num * size)) == NULL)
        err(1, "malloc");

The multiplication may lead to an integer overflow, which can be avoided using the extension Fn reallocarray , as follows:

if ((p = reallocarray(NULL, num, size)) == NULL)
        err(1, "malloc");

Alternatively Fn calloc is a more portable solution which comes with the cost of clearing memory.

If Fn malloc must be used, be sure to test for overflow:

if (size && num > SIZE_MAX / size) {
        errno = ENOMEM;
        err(1, "overflow");
}

The use of Fn reallocarray or Fn calloc is strongly encouraged when allocating multiple sized objects in order to avoid possible integer overflows.

RETURN VALUES

The Fn reallocarray function returns a pointer to the allocated space if successful; otherwise, a null pointer is returned and errno is set to Er ENOMEM .

SEE ALSO

malloc(3), calloc(3), alloca(3)

HISTORY

Fn reallocarray appeared in Ox 5.6 .