malloc(3C)                     DG/UX R4.11MU05                    malloc(3C)


NAME
       malloc, free, realloc, calloc, memalign, valloc, - memory allocator

SYNOPSIS
       #include <stdlib.h>

       void *malloc (size_t size);

       void free (void *ptr);

       void *realloc (void *ptr, size_t size);

       void *calloc (size_t nelem, size_t elsize);

       void *memalign(size_t alignment, size_t size);

       void *valloc(size_t size);

       #include <alloca.h>

       char *alloca(int size);

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, calloc or realloc.  After free is performed, this space is
       made available for further allocation.  If ptr is a NULL pointer, no
       action occurs.

       Undefined results will occur if the space assigned by malloc is
       overrun or if some random number is handed to 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 ptr
       is NULL, realloc behaves like malloc for the specified size.  If size
       is zero and ptr is not a null pointer, the object pointed to is
       freed.

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

       memalign allocates size bytes on a specified alignment boundary, and
       returns a pointer to the allocated block.  The value of the returned
       address is guaranteed to be an even multiple of alignment.  Note: the
       value of alignment must be a power of two, and must be greater than
       or equal to the size of a word.

       valloc(size) is equivalent to memalign(sysconf(_SC_PAGESIZE),size).

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

       malloc, realloc, calloc, memalign, and valloc will fail if there is
       not enough available memory.

       alloca allocates size bytes of space in the stack frame of the
       caller.  This temporary space is automatically freed on return.
       alloca is only supported by the GNU C language compiler.

   Considerations for Threads Programming
                     +---------+-----------------------------+
                     |         |                      async- |
                     |function | reentrant   cancel   cancel |
                     |         |             point     safe  |
                     +---------+-----------------------------+
                     |alloca   |     Y         N        N    |
                     |calloc   |     Y         N        N    |
                     |free     |     Y         N        N    |
                     |malloc   |     Y         N        N    |
                     |memalign |     N         -        -    |
                     |realloc  |     Y         N        N    |
                     |valloc   |     N         -        -    |
                     +---------+-----------------------------+
SEE ALSO
       reentrant(3), malloc(3X), gcc(1).

DIAGNOSTICS
       If there is no available memory, malloc, realloc, memalign, valloc,
       and calloc return a null pointer.  When realloc returns NULL, the
       block pointed to by ptr is left intact.  If size, nelem, or elsize is
       0, a unique pointer to the area is returned.

NOTES
       All of the above routines (except alloca) are intended to be used
       only within the scope of the C library's malloc implementation.  They
       will most likely not work with alternative malloc implementations.

       The valloc and memalign functions are ONLY available within ELF libc.
       They are not available in BCS, OCS or COFF libc.

       Also, unlike other implementations of valloc one may find, the
       implementation within the ELF libc library can be used with free and
       realloc.


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