MALLOC(3)                            BSD                             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 comprise 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 have been used in the past
     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 0s.

     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.

NOTES
     Developers of installed libraries should include <apollo/shlib.h> in
     those modules which use malloc, free, or realloc.  Doing so assures that
     references to these routines resolve to those defined by the application,

     if any.

SEE ALSO
     brk(2), getpagesize(2), malloc.dbg(3)

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 storing
     outside the bounds of a block.  We provide a version of malloc that
     checks the arena very stringently on every transaction.  See
     malloc.dbg(3).

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 2.

     alloca is machine dependent; its use is discouraged.