c - FUSE 文件系统在打开文件时崩溃(仅在 Release模式下)

Question

我有一些问题，我找不到解决方案:/我需要在我的 fuse 文件系统中打开一个文本文件。在调试中一切正常，但在发布系统中崩溃。我用这个做了一个简单的例子。有人能说出这段代码有什么问题吗？

/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2007  Miklos Szeredi <miklos@szeredi.hu>

  This program can be distributed under the terms of the GNU GPL.
  See the file COPYING.

  gcc -Wall `pkg-config fuse --cflags --libs` hello.c -o hello
*/
#    define FUSE_USE_VERSION 26

#include  <fuse.h>
#include  <stdio.h>
#include  <string.h>
#include  <errno.h>
#include  <fcntl.h>

void stripnl(char *str) {
  while(strlen(str) && ( (str[strlen(str) - 1] == 13) || 
       ( str[strlen(str) - 1] == 10 ))) {
    str[strlen(str) - 1] = 0;
  }
}

static const char *hello_str = "Hello World!\n";
static const char *hello_path = "/hello";

static int hello_getattr(const char *path, struct stat *stbuf)
{
    int res = 0;
    memset(stbuf, 0, sizeof(struct stat));
    if (strcmp(path, "/") == 0) {
        stbuf->st_mode = S_IFDIR | 0755;
        stbuf->st_nlink = 2;
    } else if (strcmp(path, hello_path) == 0) {
        stbuf->st_mode = S_IFREG | 0444;
        stbuf->st_nlink = 1;
        stbuf->st_size = strlen(hello_str);
    } else
        res = -ENOENT;

    return res;
}

static int hello_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
             off_t offset, struct fuse_file_info *fi)
{
    (void) offset;
    (void) fi;

    if (strcmp(path, "/") != 0)
        return -ENOENT;

    filler(buf, ".", NULL, 0);
    filler(buf, "..", NULL, 0);

    filler(buf, hello_path + 1, NULL, 0);

  FILE *infile;
  char fname[40];
  char line[100];
  int lcount;

      /* We need to get rid of the newline char. */
  stripnl(fname);

  /* Open the file.  If NULL is returned there was an error */
  if((infile = fopen("ex.txt", "r")) == NULL) {
    printf("Error Opening File.\n");
  }

  while( fgets(line, sizeof(line), infile) != NULL ) {
    /* Get each line from the infile */
    lcount++;
    /* print the line number and data */
    printf("Line %d: %s", lcount, line);  
    filler(buf, line, NULL, 0);
  }

  fclose(infile);  /* Close the file */

    return 0;
}

static int hello_open(const char *path, struct fuse_file_info *fi)
{
    if (strcmp(path, hello_path) != 0)
        return -ENOENT;

    if ((fi->flags & 3) != O_RDONLY)
        return -EACCES;

    return 0;
}

static int hello_read(const char *path, char *buf, size_t size, off_t offset,
              struct fuse_file_info *fi)
{
    size_t len;
    (void) fi;
    if(strcmp(path, hello_path) != 0)
        return -ENOENT;

    len = strlen(hello_str);
    if (offset < len) {
        if (offset + size > len)
            size = len - offset;
        memcpy(buf, hello_str + offset, size);
    } else
        size = 0;

    return size;
}

static struct fuse_operations hello_oper = {
    .getattr    = hello_getattr,
    .readdir    = hello_readdir,
    .open       = hello_open,
    .read       = hello_read,
};

int main(int argc, char *argv[])
{
    return fuse_main(argc, argv, &hello_oper, NULL);
}

更新

好的，我找到了解决方案，路径必须是绝对文件路径(不确定这句话是否正确)，但这里是示例代码，它在发布和调试中都有效:

/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2007  Miklos Szeredi <miklos@szeredi.hu>

  This program can be distributed under the terms of the GNU GPL.
  See the file COPYING.

  gcc -Wall `pkg-config fuse --cflags --libs` hello.c -o hello
*/
#    define FUSE_USE_VERSION 26

#include  <fuse.h>
#include  <stdio.h>
#include  <string.h>
#include  <errno.h>
#include  <fcntl.h>

void stripnl(char *str) {
  while(strlen(str) && ( (str[strlen(str) - 1] == 13) || 
       ( str[strlen(str) - 1] == 10 ))) {
    str[strlen(str) - 1] = 0;
  }
}

static const char *hello_str = "Hello World!\n";
static const char *hello_path = "/hello";

static int hello_getattr(const char *path, struct stat *stbuf)
{
    int res = 0;
    memset(stbuf, 0, sizeof(struct stat));
    if (strcmp(path, "/") == 0) {
        stbuf->st_mode = S_IFDIR | 0755;
        stbuf->st_nlink = 2;
    } else if (strcmp(path, hello_path) == 0) {
        stbuf->st_mode = S_IFREG | 0444;
        stbuf->st_nlink = 1;
        stbuf->st_size = strlen(hello_str);
    } else
        res = -ENOENT;

    return res;
}

static int hello_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
             off_t offset, struct fuse_file_info *fi)
{
    (void) offset;
    (void) fi;

    if (strcmp(path, "/") != 0)
        return -ENOENT;

    filler(buf, ".", NULL, 0);
    filler(buf, "..", NULL, 0);

    filler(buf, hello_path + 1, NULL, 0);

    FILE *infile;
    char line[100];

    if((infile = fopen("/root/Desktop/fexamples/ex.txt", "rb")) == NULL) 
    {
        return -1;
    }

    while( fgets(line, sizeof(line), infile) != NULL ) 
    {
            filler(buf, line, NULL, 0);
    }

    fclose(infile);  /* Close the file */

    return 0;
}

static int hello_open(const char *path, struct fuse_file_info *fi)
{
    if (strcmp(path, hello_path) != 0)
        return -ENOENT;

    if ((fi->flags & 3) != O_RDONLY)
        return -EACCES;

    return 0;
}

static int hello_read(const char *path, char *buf, size_t size, off_t offset,
              struct fuse_file_info *fi)
{
    size_t len;
    (void) fi;
    if(strcmp(path, hello_path) != 0)
        return -ENOENT;

    len = strlen(hello_str);
    if (offset < len) {
        if (offset + size > len)
            size = len - offset;
        memcpy(buf, hello_str + offset, size);
    } else
        size = 0;

    return size;
}

static struct fuse_operations hello_oper = {
    .getattr    = hello_getattr,
    .readdir    = hello_readdir,
    .open       = hello_open,
    .read       = hello_read,
};

int main(int argc, char *argv[])
{
    return fuse_main(argc, argv, &hello_oper, NULL);
}

Answer 1

您的 readdir 实现中至少有两个问题。

char fname[40];
char line[100];
int lcount;

/* We need to get rid of the newline char. */
stripnl(fname);

您正在对您未在任何地方初始化的 fname 的内容进行操作。这几乎可以做任何事情。在那之后您没有使用 fname 的事实是无关紧要的，您可以使用该 stripnl 调用修改完全随机的数据。

/* Open the file.  If NULL is returned there was an error */
if((infile = fopen("ex.txt", "r")) == NULL) {
    printf("Error Opening File.\n");
}

如果 fopen 失败，您应该错误地退出(或直接离开)这个函数。否则，下一行将以 NULL 作为文件参数调用 fgets。