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)

malloc(3)						     Library Functions Manual							 malloc(3)

Name
       malloc, free, realloc, calloc, alloca - memory allocator

Syntax
       char *malloc(size)
       unsigned size;

       free(ptr)
       void *ptr;

       char *realloc(ptr, size)
       void *ptr;
       unsigned size;

       char *calloc(nelem, elsize)
       unsigned nelem, elsize;

       char *alloca(size)
       int size;

Description
       The  and  subroutines  provide a simple general-purpose memory allocation package.  The subroutine returns a pointer to a block of at least
       size bytes beginning on a word boundary.

       The argument to is a pointer to a block previously allocated by 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 is overrun or if some random number is handed to

       The subroutine maintains multiple lists of free blocks according to size, allocating space from the appropriate list.  It calls to get more
       memory from the system when there is no suitable space already free.  For further information, see

       The subroutine changes the size of the block pointed to by ptr to size bytes and returns a pointer to the (possibly moved) block.  The con-
       tents will be unchanged up to the lesser of the new and old sizes.

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

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

       The subroutine allocates size bytes of space associated with the stack frame of the caller.  This temporary space is  available	for  reuse
       when  the  caller returns.  On MIPS machines, calling reclaims all available storage.  On VAX machines, the 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.

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

       Currently,  the	allocator is unsuitable for direct use in a large virtual environment where many small blocks are kept, since it keeps all
       allocated and freed blocks on a circular list.  Just before more memory is allocated, all allocated and freed blocks are referenced.

       Because the subroutine is machine dependent, its use should be avoided.

Diagnostics
       The and subroutines return a null pointer (0) if there is no available memory or if the arena has been detectably corrupted by storing out-
       side the bounds of a block.

								       RISC								 malloc(3)