在gcc编译器中malloc与calloc它们都是实现内存分配。但是也有点小区别，就是malloc分配内存不会将数据清零，而calloc则会将数据清零。
源码
bzero(ptr,nelem*elsize)是将ptr的前nelem * elsize个字节置为0。- gcc-4.7.1 calloc函数源代码
/* 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;
}
