malloc与calloc

/* calloc -- allocate memory which has been initialized to zero.
   This function is in the public domain. */

/*

@deftypefn Supplemental void* calloc (size_t @var{nelem}, size_t @var{elsize})

Uses @code{malloc} to allocate storage for @var{nelem} objects of
@var{elsize} bytes each, then zeros the memory.

@end deftypefn

*/

#include "ansidecl.h"
#include <stddef.h>

/* For systems with larger pointers than ints, this must be declared.  */
PTR malloc (size_t);
void bzero (PTR, size_t);

PTR calloc (size_t nelem, size_t elsize)
{
    register PTR ptr;  

    if (nelem == 0 || elsize == 0)
        nelem = elsize = 1;

    ptr = malloc (nelem * elsize);
    if (ptr) bzero (ptr, nelem * elsize);

    return ptr;
}