malloc(3) [v7 man page]

MALLOC(3)						     Library Functions Manual							 MALLOC(3)

NAME

       malloc, free, realloc, calloc - main 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;

DESCRIPTION

       Malloc  and  free  provide  a simple 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  allocates  the  first  big enough contiguous reach of free space found in a circular search from the last block allocated or freed,
       coalescing adjacent free blocks as it searches.	It calls sbrk (see break(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.

       Realloc also works if ptr points to a block freed since the last call of malloc, realloc or calloc; thus  sequences  of	free,  malloc  and
       realloc can exploit the search strategy of malloc to do storage compaction.

       Calloc allocates space for an array of nelem elements of size elsize.  The space is initialized to zeros.

       Each  of  the  allocation routines returns a pointer to space suitably aligned (after possible pointer coercion) for storage of any type of
       object.

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; see the source code.

BUGS

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

																	 MALLOC(3)

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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)

Linux and UNIX Man Pages

malloc(3) [v7 man page]

Check Out this Related Man Page