MALLOC(3C)      (C Programming Language Utilities)     MALLOC(3C)



  NAME
       malloc, free, realloc, calloc - main memory allocator

  SYNOPSIS
       char *malloc (size)
       unsigned size;

       void 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 suitably aligned for any use.

       The argument to free is a pointer to a block previously
       allocated by malloc; after free is performed this space is
       made available for further allocation, but its contents are
       left undisturbed.

       Undefined results will occur 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 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


  Page 1                                                   May 1989

  MALLOC(3C)      (C Programming Language Utilities)     MALLOC(3C)



       the new and old sizes.  If no free block of size bytes is
       available in the storage arena, then realloc will ask malloc
       to enlarge the arena by size bytes and will then move the
       data to the new space.

       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.

  SEE ALSO
       brk(2), malloc(3X).

  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.  When
       this happens the block pointed to by ptr may be destroyed.

  NOTES
       Search time increases when many objects have been allocated;
       that is, if a program allocates but never frees, then each
       successive allocation takes longer.  For an alternate, more
       flexible implementation, see malloc(3X).











  Page 2                                                   May 1989