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MALLOC(3V) C LIBRARY FUNCTIONS MALLOC(3V)
NAME
malloc, free, realloc, calloc
SYNOPSIS
#include <malloc.h>
void *malloc(size)
size_t size;
void free(ptr)
void *ptr;
void *realloc(ptr, size)
void *ptr;
size_t size;
void *calloc(nelem, elsize)
size_t nelem;
size_t elsize;
DESCRIPTION
These routines provide a general-purpose memory allocation
package. They maintain a table of free blocks for efficient
allocation and coalescing of free storage. When there is no
suitable space already free, the allocation routines call
rn_getseg() to get more memory from the system.
Each of the allocation routines returns a pointer to space
suitably aligned for storage of any type of object. Each
returns a NULL pointer if the request cannot be completed
(see DIAGNOSTICS).
malloc() returns a pointer to a block of at least size
bytes, which is appropriately aligned.
free() releases a previously allocated block. Its argument
is a pointer to a block previously allocated by malloc(),
calloc() or realloc().
realloc() changes the size of the block referenced 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 unable to honor a reallocation
request, realloc() leaves its first argument unaltered.
**** DMALLOC DOES NOT COMPLY WITH THE PARAGRAPH BELOW ****
For backwards compatibility, realloc() accepts a pointer to a
block freed since the most recent call to malloc(), cal-
loc() or realloc().
Note: using realloc() with a block freed before the most recent
call to malloc(), calloc() or realloc() is an error.
calloc() uses malloc() to allocate space for an array of
nelem elements of size elsize, initializes the space to
zeros, and returns a pointer to the initialized block. The
block should be freed with free().
malloc() and realloc() return a non- NULL pointer if size is 0,
and calloc() returns a non-NULL pointer if nelem or elsize is 0,
but these pointers should not be dereferenced.
Note: Always cast the value returned by malloc(), realloc() or
calloc().
RETURN VALUES On success, malloc(), calloc() and realloc() return a
pointer to space suitably aligned for storage of any type of
object. On failure, they return NULL.
free() does not return a value.
NOTES
Because malloc() and realloc() return a non-NULL pointer if size
is 0, and calloc() returns a non-NULL pointer if nelem or elsize
is 0, a zero size need not be treated as a special case if it
should be passed to these functions unpredictably. Also, the
pointer returned by these functions may be passed to subsequent
invocations of realloc().
BUGS
**** DMALLOC DOES NOT COMPLY WITH THE PARAGRAPH BELOW ****
Since realloc() accepts a pointer to a block freed since the last
call to malloc(), calloc() or realloc(), a degradation of
performance results. The semantics of free() should be changed
so that the contents of a previously freed block are undefined.
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