realloc(3) [bsd man page]

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)

Check Out this Related 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)

Linux and UNIX Man Pages

realloc(3) [bsd man page]

Check Out this Related Man Page