malloc与calloc

发表于

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
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    /* 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;
    }