NAME

malloc, free, realloc, calloc, memalign, valloc, − memory allocator

SYNOPSIS

#include <stdlib.h>

void ∗malloc (size_t size);

void free (void ∗ptr);

void ∗realloc (void ∗ptr, size_t size);

void ∗calloc (size_t nelem, size_t elsize);

void ∗memalign(size_t alignment, size_t size);

void ∗valloc(size_t size);

DESCRIPTION

malloc and free provide a simple general-purpose memory allocation package.  malloc returns a pointer to a block of at least size bytes suitably aligned for any use. 

The argument to free is a pointer to a block previously allocated by malloc, calloc or realloc.  After free is performed this space is made available for further allocation.  If ptr is a NULL pointer, no action occurs. 

Undefined results will occur if the space assigned by malloc is overrun or if some random number is handed to free. 

realloc changes the size of the block pointed to by ptr to size bytes and returns a pointer to the (possibly moved) block.  The contents will be unchanged up to the lesser of the new and old sizes.  If ptr is NULL, realloc behaves like malloc for the specified size.  If size is zero and ptr is not a null pointer, the object pointed to is freed. 

calloc allocates space for an array of nelem elements of size elsize. The space is initialized to zeros.

memalign allocates size bytes on a specified alignment boundary, and returns a pointer to the allocated block.  The value of the returned address is guaranteed to be an even multiple of alignment.  Note: the value of alignment must be a power of two, and must be greater than or equal to the size of a word. 

valloc(size) is equivalent to memalign(sysconf(_SC_PAGESIZE),size). 

Each of the allocation routines returns a pointer to space suitably aligned (after possible pointer coercion) for storage of any type of object. 

malloc, realloc, calloc, memalign, and valloc will fail if there is not enough available memory. 

SEE ALSO

malloc(3X)

DIAGNOSTICS

If there is no available memory, malloc, realloc, memalign, valloc, and calloc return a null pointer.  When realloc returns NULL, the block pointed to by ptr is left intact.  If size, nelem, or elsize is 0, a unique pointer to the arena is returned. 

  —  C Development Set