


      MALLOC(3C)                  (UNIX 5.0)                 MALLOC(3C)



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

      SYNTAX
           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.  On the
           Bull-SPS9, blocks obtained from malloc are aligned on even
           8-byte boundaries.

           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
           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.




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      MALLOC(3C)                  (UNIX 5.0)                 MALLOC(3C)



           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.

      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.

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






































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