c - 额外的memset()导致系统调用open()失败

我已经按照教程here (chardev.c)在/dev中创建了一个节点，我尝试使用以下代码访问/dev/chardev中创建的设备：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h> //perror(), errno
#include <string.h>
#define RSIZE 50

int main()
{
    int fd,err_save;
    char receive_buff[RSIZE];

    //open device and check for error msg
    fd = open("/dev/chardev", "rw");
    err_save = errno;
    if (fd < 0)
        {
        perror("open perror");
        printf("error opening device, fd = %d, err_save = %d \n", fd,err_save);
        }
    else
        {printf("Device opened\n");}

    //read device and check for error msg
    //memset(receive_buff, 0, sizeof(receive_buff)); //<--- strange
    read(fd, receive_buff, RSIZE);
    err_save = errno;
        if (fd < 0)
        {
        perror("read perror");
        printf("error reading device, fd = %d, err_save = %d \n", fd,err_save);
        }
    else
        {
        printf("Device read successful : %s\n",receive_buff);}

    //close device and check for error msg
    fd = close(fd);
    err_save = errno;
    if (fd < 0)
        {
        perror("close perror");
        printf("error closing device, fd = %d, err_save = %d \n", fd,err_save);
        }
    else
        {printf("Device closed\n");}
    return 0;
}

成功结果：

Device opened
Device read successful : I already told you 7 times Hello world!
w�0 ����
Device closed

但是，当memset(receive_buff, 0, sizeof(receive_buff));未注释时，我得到以下结果：

open perror: File exists
error opening device, fd = -1, err_save = 17
read perror: Bad file descriptor
error reading device, fd = -1, err_save = 9
close perror: Bad file descriptor
error closing device, fd = -1, err_save = 9

问题：附加的memset()如何导致open()失败？

最佳答案

open将整数作为第二个参数（您会将其与fopen混淆）。您的open行应该是：

fd = open("/dev/chardev", O_RDWR);

当代码被添加和删除时，它工作或失败的原因必须与地址"rw"的不可预测值有关，当open被删除时，该值可能恰好是memset的有效值。

关于c - 额外的memset()导致系统调用open()失败，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/7328602/