memcpy然后是printf，调用stat()，写入缓冲区； [英] memcpy and then printf, calling stat(), writing in buffer;

问题描述

这是包含项和我的功能:

here are includes and my function:

我正在尝试使用memcpy在缓冲区中复制stbuf->st_mode，并且在读回时，值不是我要复制的内容.

I'm trying to copy stbuf->st_mode in buffer with memcpy and when reading it back, value is not what I was trying to copy.

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <string.h>

void r1_getattr(char* pth, int cfd){
    struct stat* stbuf = malloc(sizeof(stat));

    int res = stat(pth, stbuf);

    printf("(%3o)\n", (stbuf->st_mode)&0777);
    char* wbuf = malloc(256);

    memcpy(wbuf, &(stbuf->st_mode), sizeof(mode_t));
    printf("(%3o)\n", (*(mode_t*)((char*)wbuf))&0777);
}

输出:(775)"和(21)"不应该相同吗?

outputs: "(775)" and "( 21)" shouldn't they be the same?

推荐答案

简单的键入错误:

替换

struct stat *stbuf = malloc(sizeof(stat));

使用

struct stat *stbuf = malloc(sizeof(struct stat));

当我们使用未初始化的内存时看到奇怪的结果总是很有趣:-)

Always funny to see the weird results we get when we use un-initialized memory :-)

这篇关于memcpy然后是printf，调用stat()，写入缓冲区；的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！