MALLOC(2) MALLOC(2)
NAME
malloc, free, realloc, calloc - memory allocator
SYNOPSIS
#include <u.h>
#include <libc.h>
void* malloc(long size)
void free(void *ptr)
void* realloc(void *ptr, long size)
void* calloc(long nelem, long elsize)
DESCRIPTION
Malloc and free provide a simple memory allocation package.
Malloc returns a pointer to a new block of at least size
bytes. The block is suitably aligned for storage of any
type of object. No two active pointers from malloc will
have the same value.
The argument to free is a pointer to a block previously
allocated by malloc; this space is made available for fur-
ther allocation. It is legal to free a null pointer; the
effect is a no-op.
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. The call realloc(0, size) means the
same as `malloc(size)'.
Calloc allocates space for an array of nelem elements of
size elsize. The space is initialized to zeros. Free frees
such a block.
Alef
Except for calloc, these routines are available from Alef;
they use the same arena as alloc. Malloc and realloc exe-
cute a check when they fail, rather than return nil. Memory
returned by malloc is cleared. Realloc does not guarantee
new memory is cleared unless ptr is nil.
SOURCE
/sys/src/libc/port/malloc.c
SEE ALSO
brk(2)
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MALLOC(2) MALLOC(2)
DIAGNOSTICS
Malloc, realloc and calloc return 0 if there is no available
memory. Errstr is likely to be set.
BUGS
The different specification of calloc is bizarre.
User errors can corrupt the storage arena. The most common
gaffes are (1) freeing an already freed block, (2) storing
beyond the bounds of an allocated block, and (3) freeing
data that was not obtained from the allocator. When malloc
and free detect such corruption, they abort.
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