MALLOC(3C-SVR3)     RISC/os Reference Manual      MALLOC(3C-SVR3)



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

SYNOPSIS
     #include <bsd/sys/types.h>

     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
     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-SVR3)     RISC/os Reference Manual      MALLOC(3C-SVR3)



     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), malloccheck(3).

DIAGNOSTICS
     malloc, realloc and calloc return a NULL pointer if there is
     no available memory or if the arena has been detectably cor-
     rupted 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).


































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