MALLOC(3) MALLOC(3)
NAME
malloc, free, realloc, calloc, cfree - memory allocator
SYNOPSIS
char *malloc(size)
unsigned size;
free(ptr)
char *ptr;
char *realloc(ptr, size)
char *ptr;
unsigned size;
char *calloc(nelem, elsize)
unsigned nelem, elsize;
cfree(ptr)
char *ptr;
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.
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((char*)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. Cfree frees
such a block.
SEE ALSO
galloc(3), brk(2), pool(3), block(3)
DIAGNOSTICS
Malloc, realloc and calloc return 0 if there is no available
memory or if the arena has been detectably corrupted.
BUGS
When realloc returns 0, the block pointed to by ptr may have
MALLOC(3) MALLOC(3)
been destroyed.
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. To help find
such errors, a diagnosing allocator may be loaded; use flag
-ldmalloc of cc(1). An even more stringently checking ver-
sion may be created by recompilation; see the source.