NAME
malloc, free, realloc, calloc, alloca - memory allocator
SYNOPSIS
#include <sys/types.h>
#include <stdlib.h>
#include <alloca.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 *alloca(size_t size)
DESCRIPTION
Malloc and free provide a general-purpose memory allocation
package. Malloc returns a pointer to a block of at least
size bytes beginning on a word boundary.
The argument to free is a pointer to a block previously
allocated by malloc; this space is made available for
further allocation, but its contents are left undisturbed.
A call with a null ptr is legal and does nothing.
Needless to say, grave disorder will result if the space
assigned by malloc is overrun or if some random number is
handed to free.
Malloc maintains multiple lists of free blocks according to
size, allocating space from the appropriate list. It calls
sbrk (see brk(2)) to get more memory from the system when
there is no suitable space already 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. A call with a null ptr is legal and
has the same result as malloc(size).
Calloc allocates space for an array of nelem elements of
size elsize. The space is initialized to zeros.
Alloca allocates size bytes of space in the stack frame of
the caller. This temporary space is automatically freed on
return.
Each of the allocation routines returns a pointer to space
suitably aligned (after possible pointer coercion) for
storage of any type of object.
SEE ALSO
brk(2).
DIAGNOSTICS
Malloc, realloc and calloc return a null pointer if there is
no available memory or if the arena has been detectably cor-
rupted by storing outside the bounds of a block.
NOTES
Other implementations of malloc, realloc or calloc may
return a null pointer if the size of the requested block is
zero. This implementation will always return a zero length
block at a unique address, but you should keep in mind that
a null return is possible if the program is run to another
system and that this should not be mistakenly seen as an
error.
BUGS
When realloc returns a null pointer, the block pointed to by
ptr may be destroyed.
Alloca is machine dependent; its use is discouraged.