MAPMALLOC(3MALLOC) Memory Allocation Library Functions MAPMALLOC(3MALLOC)
NAME
mapmalloc - memory allocator
SYNOPSIS
cc [
flag ... ]
file ...
-lmapmalloc [
library ... ]
#include <stdlib.h>
void *malloc(
size_t size);
void *calloc(
size_t nelem,
size_t elsize);
void free(
void * ptr);
void *realloc(
void *ptr,
size_t size);
DESCRIPTION
The collection of
malloc functions in this library use
mmap(2) instead of
sbrk(2) for acquiring new heap space. The functions in
this library are intended to be used only if necessary, when
applications must call
sbrk(), but need to call other library
routines that might call
malloc. The algorithms used by these
functions are not sophisticated. There is no reclaiming of memory.
The
malloc() and
free() functions provide a simple general-purpose
memory allocation package.
The
malloc() function 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(). 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().
The
calloc() function allocates space for an array of
nelem elements
of size
elsize. The space is initialized to zeros.
The
realloc() function 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 the new size of the block requires movement of the
block, the space for the previous instantiation of the block is
freed. If the new size is larger, the contents of the newly allocated
portion of the block are unspecified. If
ptr is
NULL,
realloc() behaves like
malloc() for the specified size. If
size is 0 and
ptr is
not a null pointer, the space pointed to is freed.
Each of the allocation functions returns a pointer to space suitably
aligned (after possible pointer coercion) for storage of any type of
object.
The
malloc() and
realloc() functions will fail if there is not enough
available memory.
Entry points for
malloc_debug(),
mallocmap(),
mallopt(),
mallinfo(),
memalign(), and
valloc() are empty routines, and are provided only to
protect the user from mixing
malloc() functions from different
implementations.
RETURN VALUES
If there is no available memory,
malloc(),
realloc(), 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.
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+---------------+-----------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-----------------+
|MT-Level | Safe |
+---------------+-----------------+
SEE ALSO
brk(2),
getrlimit(2),
mmap(2),
realloc(3C),
malloc(3MALLOC),
attributes(7) February 20, 2004 MAPMALLOC(3MALLOC)
