栈内存不是只有2M吗？为什么不溢出？

#include <stdio.h>
#include <wchar.h>
#include <stdlib.h>

#define MAX_PATH 1024

FILE* wfopen(const wchar_t* filename, const wchar_t* mode)
{
    char fn[MAX_PATH];
    char m[MAX_PATH];
    wcstombs(fn, filename, MAX_PATH);
    wcstombs(m, mode, MAX_PATH);
    return fopen(fn, m);
}

http://www.cnblogs.com/SunWentao/archive/2008/11/03/1325687.html