Visit Our UNIX and Linux User Community

Linux and UNIX Man Pages

Test Your Knowledge in Computers #213
Difficulty: Medium
OSPF-TE is an extension to OSPF extending the expressivity to allow for traffic engineering and use on non-IP networks.
True or False?
Linux & Unix Commands - Search Man Pages

malloc(3) [minix man page]

MALLOC(3)						     Library Functions Manual							 MALLOC(3)

NAME
malloc, free, realloc, calloc, alloca - memory allocator SYNOPSIS
#include <sys/types.h> #include <stdlib.h> #include <alloca.h> void *malloc(size_t size) void free(void *ptr) void *realloc(void *ptr, size_t size) void *calloc(size_t nelem, size_t elsize) void *alloca(size_t 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. A call with a null ptr is legal and does nothing. 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. A call with a null ptr is legal and has the same result as malloc(size). 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. SEE ALSO
brk(2). DIAGNOSTICS
Malloc, realloc and calloc return a null pointer if there is no available memory or if the arena has been detectably corrupted by storing outside the bounds of a block. NOTES
Other implementations of malloc, realloc or calloc may return a null pointer if the size of the requested block is zero. This implementa- tion will always return a zero length block at a unique address, but you should keep in mind that a null return is possible if the program is run to another system and that this should not be mistakenly seen as an error. BUGS
When realloc returns a null pointer, the block pointed to by ptr may be destroyed. 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, 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)

Featured Tech Videos