无法获取段错误的原因

Question

编辑：请注意并不是说我不能访问main()中由storeContents()分配的内存，如果你这么认为的话。 storeContents()

执行期间程序崩溃

程序在这里失败:

strcpy(contents[count], dir->d_name);
printf("Stored %s(out hiddenVisible)\n", dir->d_name); // for testing

是strcpy()不是printf()，我添加它只是为了参考。

调试器 (gdb) 说：

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7f3cd72 in __strcpy_ssse3 () from /usr/lib/libc.so.6

我正在制作一个涉及以下功能的程序"storeContents"（它将目录的内容名称存储在动态数组中）。此功能有两个问题：(1) 它说“Stored file_name”两次 文件和 (2) 显示“分段错误”。我无法弄清楚他们中的任何一个。感谢您的努力！

#include <stdio.h>
#include <string.h>
#include <dirent.h>
#include <stdlib.h>
#include <sys/types.h>
#include <limits.h>

static short hiddenVisible = 0;

/* Store directory's contents in **contents */
static char ** storeContents(struct dirent *dir, DIR *dirp, unsigned numOfContents);
/* Count files/directories in a directory */
static unsigned getNumOfContents(struct dirent *dir, DIR *dirp);

int main(int argc, char const *argv[])
{
    char **contents;
    DIR *dirp;
    struct dirent *dir;
    unsigned numOfContents;

    dirp = opendir("/home/gaurav");
    if((dir = readdir(dirp)) == NULL) {
        perror("readdir");
        exit(1);
    }

    /* Getting number of files/directories */
    numOfContents = getNumOfContents(dir, dirp);
    printf("There are %u files.\n", numOfContents);

    /* To position again to the first entry */
    rewinddir(dirp);

    contents = storeContents(dir, dirp, numOfContents);

    /* Print contents */
    for(unsigned i = 0; i < numOfContents; ++i)
        printf("%s\n", contents[i]);

    closedir(dirp);
    return 0;
}

char **
storeContents(struct dirent *dir, DIR *dirp, unsigned numOfContents) {

    char **contents;
    unsigned count = 0;

    /* Allocating memory for entries */
    contents = malloc(numOfContents * sizeof(*contents));

    /* Allocating memory for each '*contents' */
    for(unsigned i = 0; i < numOfContents; i++)
        contents[i] = (char *)malloc(NAME_MAX); /* we know char is 1 byte, so no "sizeof" */

    while(count < numOfContents) {
        /* Ignore "." and ".." */
        if(!(strcmp(dir->d_name, ".")) || !(strcmp(dir->d_name, ".."))) {
            if((dir = readdir(dirp)) == NULL) {
                perror("readdir");
                exit(1);
            }
            continue;
        }

        if(hiddenVisible) {
            strcpy(contents[count], dir->d_name);
            if((dir = readdir(dirp)) == NULL) {
                perror("readdir");
                exit(1);
            }
            count++;
        } else {
            if(dir->d_name[0] == '.')
                if((dir = readdir(dirp)) == NULL) {
                    perror("readdir");
                    exit(1);
                }
                else {
                    strcpy(contents[count], dir->d_name);
                    if((dir = readdir(dirp)) == NULL) {
                        perror("readdir");
                        exit(1);
                    }
                    count++;
                }
        }
    }
    return contents;
}

unsigned
getNumOfContents(struct dirent *dir, DIR *dirp) {

    unsigned count = 0;

    while(dir) {
        if(hiddenVisible) {
            /* Ignore "." and ".." */
            if(!(strcmp(dir->d_name, ".")) || !(strcmp(dir->d_name, ".."))) {
                if((dir = readdir(dirp)) == NULL) {
                    perror("readdir a");
                    exit(1);
                }
                continue;
            }
            count++;
            if((dir = readdir(dirp)) == NULL) {
                perror("readdir b");
                exit(1);
            }
        } else {
            if(dir->d_name[0] == '.') {
                if((dir = readdir(dirp)) == NULL) {
                    perror("readdir c");
                    exit(1);
                }
            }
                else {
                    count++;
                    if((dir = readdir(dirp)) == NULL) {
                        perror("readdir d");
                        exit(1);
                    }
                }
        }
    }

    return count;
}

Answer 1

函数 storeContents 中的

contents 是 main.

中 contents 的本地副本

在函数中更改它不会更改 main 中的变量。

你应该return数组。变化
static void storeContents(struct dirent *dir, DIR *dirp, char **contents, unsigned numOfContents);
至
static char **storeContents(struct dirent *dir, DIR *dirp, unsigned numOfContents);

,return contents; 在函数中并像 char **contents = storeContents(...);

那样调用它

Answer 2

一些错误：

contents 是函数的局部参数，它不会 returned 到 main()。参见。
contents = (char **)malloc(numOfContents);是错误的，需要给numOfContents指针分配空间。将其更改为 contents = malloc(numOfContents * sizeof(*contents)).
您应该检查对 readdir 的每次调用并确保它没有 return NULL.

无法获取段错误的原因

Can't get the reason for segfault

c

malloc

dynamic-arrays