malloc(3C)                                             malloc(3C)



     NAME
          malloc, free, realloc, calloc, cfree - 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;

          void cfree(ptr,nelem,elsize)
          char *ptr;
          unsigned nelem, elsize;

     DESCRIPTION
          malloc and free provide a simple general-purpose memory al-
          location 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 al-
          located by malloc; after free is performed, this space is
          made available for further allocation, but its contents are
          left undisturbed.

          Undefined results occur if the space assigned by malloc is
          overrun or if some random number is handed to free.

          malloc allocates the first contiguous reach of free space of
          sufficient size found in a circular search from the last
          block allocated or freed; it coalesces 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 al-
          ready 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 are unchanged up to the lesser of the
          new and old sizes.  If no free block of size bytes is avail-
          able in the storage arena, realloc asks malloc to enlarge
          the arena by size bytes and then moves 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



     April, 1990                                                     1

     malloc(3C)                                             malloc(3C)



          malloc to do storage compaction.

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

          The arguments to cfree are the pointer to a block previously
          allocated by calloc plus the parameters to calloc.

          Each of the allocation routines returns a pointer to space
          suitably aligned (after possible pointer coercion) for
          storage of any type of object.

     RETURN VALUE
          malloc, realloc, and calloc return a NULL pointer if there
          is no available memory or if the arena is detected to have
          been corrupted by storing outside the bounds of a block.
          When this happens the block pointed to by ptr may be des-
          troyed.

     NOTES
          Search time increases when many objects have been allocated;
          that is, if a program allocates space but never frees it,
          each successive allocation takes longer.

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





























     2                                                     April, 1990