malloc(2) [plan9 man page]

MALLOC(2)							System Calls Manual							 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 further  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

       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 execute 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)

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.

																	 MALLOC(2)

MALLOC(3)						     Library Functions Manual							 MALLOC(3)

NAME

       malloc, free, realloc, calloc, alloca - 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;

       char *alloca(size)
       int 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.

       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.

       In  order to be compatible with older versions, realloc also works if ptr points to a block freed since the last call of malloc, realloc or
       calloc; sequences of free, malloc and realloc were previously used to attempt storage compaction.  This procedure is no longer recommended.

       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.	If the space is of pagesize or larger, the memory returned will be page-aligned.

SEE ALSO

       brk(2), pagesize(2)

DIAGNOSTICS

       Malloc, realloc and calloc return a null pointer (0) if there is no available memory or if the arena has been detectably corrupted by stor-
       ing outside the bounds of a block.  Malloc may be recompiled to check the arena very stringently on every transaction; those sites  with  a
       source code license may check the source code to see how this can be done.

BUGS

       When realloc returns 0, the block pointed to by ptr may be destroyed.

       The  current  implementation  of  malloc does not always fail gracefully when system memory limits are approached.  It may fail to allocate
       memory when larger free blocks could be broken up, or when limits are exceeded because the size is rounded up.  It is optimized	for  sizes
       that are powers of two.

       Alloca is machine dependent; its use is discouraged.

4th Berkeley Distribution					   May 14, 1986 							 MALLOC(3)