malloc(3)                           CLIX                           malloc(3)



  NAME

    malloc, free, realloc, calloc - Allocates main memory

  LIBRARY

    Standard C Library (libc.a)

  SYNOPSIS

    char *malloc(
      unsigned size );

    void free(
      char *ptr );

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

    char *calloc(
      unsigned nelem ,
      unsigned elsize );

  PARAMETERS

    elsize   Specifies the size of an array element.

    nelem    Specifies the number of elements in an array.

    ptr      Points to the allocated block of memory.

    size     Specifies the number of bytes of memory allocated.

  DESCRIPTION

    The functions described in this manual page are based in the Standard C
    Library (libc.a).  For information about the malloc() function and related
    functions based in the Malloc Library (libmalloc.a), see the other
    malloc(3) reference manual entry.

    The malloc() and free() functions provide a simple general-purpose memory
    allocation package.  The malloc() function 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 occur if the space assigned by malloc() is overrun or if
    a random number is handed to free().



  2/94 - Intergraph Corporation                                              1

  malloc(3)                           CLIX                           malloc(3)



    The malloc() function allocates the first big-enough contiguous reach of
    free space (found in a circular search from the last block allocated or
    freed) and combines adjacent free blocks as it searches.  It calls sbrk()
    (see brk()) for more system memory when suitable free space is lacking.

    The realloc() function changes the block size 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 exits in the storage arena, realloc() asks malloc() to
    enlarge the arena by size bytes and then moves the data to the new space.

    The realloc() function 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.

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

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

  EXAMPLES

    To allot 20 memory bytes pointed to by p:

    #include <stdlib.h>
    main()
    {
         char *p;

         if ((p = malloc(20)) == NULL) {
              printf("allocation error - aborting\n");
              exit(0);
         }
    }


  FILES

    stdlib.h

  NOTES

    Search time increases as more objects are allotted; that is, if a program
    allots but never frees, successive allocations take longer.  For a more
    flexible implementation see malloc().

  RETURN VALUES




  2                                              Intergraph Corporation - 2/94

  malloc(3)                           CLIX                           malloc(3)



    The malloc(), realloc(), and calloc() functions return a pointer to the
    first byte of allotted memory.  If insufficient memory exits for the
    request or if the area is detectably corrupted by storing outside the
    block bounds, a NULL pointer returns.

  RELATED INFORMATION

    Functions:  brk(2), malloc(3)














































  2/94 - Intergraph Corporation                                              3