执行 strcpy 时出现分段错误

Question

我已经开始学习C，并且一直在做一些小程序来学习。现在我正处于内存指针的阶段，我有一个快速的问题。

据我所知，我在下面编写的程序导航到 /proc/sys/net/ipv4/conf/ 目录并打印出那里列出的目录。我的意图是在函数 getSysctlNames() 中分配内存，然后在调用者 main() 中释放它。 getSysctlNames() 还应该 return 它找到的目录名称的数量。我读到过这不是最好的主意（在函数中分配并从调用者处解除分配），但我只是想愚弄和学习而不是遵循一种模式。我的问题是我在第 55 行遇到分段错误，而运行 strcpy 函数。我不确定我做错了什么。如有任何帮助，我们将不胜感激！

int getSysctlNames(char** namesPointer);

int main(int argc, char **argv) {
    char** namesPointer;
    int numberOfNames = getSysctlNames(namesPointer);
    printf("Number of files: %i\n", numberOfNames);
    int i = 0;
    for (i = 0; i <= numberOfNames; i++) {
        printf("%s\n", namesPointer[i]);
        free(namesPointer[i]);

    }
    free(namesPointer);
    return 0;
}

int getSysctlNames(char** namesPointer) {
    int numberOfNames = 0;
    DIR *directory = opendir("/proc/sys/net/ipv4/conf/");
    if (directory) {
        struct dirent *directoryEntry;
        while ((directoryEntry = readdir(directory)) != NULL) {
            if (strcmp(directoryEntry->d_name, ".") != 0 &&
                strcmp(directoryEntry->d_name, "..") != 0) {
                numberOfNames++;
            }
        }
        closedir(directory);
    } else {
        return -1;
    }
    if (numberOfNames == 0) return 0;
    namesPointer = (char**) malloc(numberOfNames * sizeof(char*));
    if (namesPointer == NULL) {
        return -1;
    }
    directory = opendir("/proc/sys/net/ipv4/conf/");
    if (directory) {
        struct dirent *directoryEntry;
        int i = 0;
        while ((directoryEntry = readdir(directory)) != NULL) {
            if (strcmp(directoryEntry->d_name, ".") != 0 &&
                strcmp(directoryEntry->d_name, "..") != 0) {
                namesPointer[i] = malloc((strlen(directoryEntry->d_name) + 1) * sizeof(char));
                if (namesPointer[i] = NULL) {
                    int j = i - 1;
                    while (j >= 0) {
                        free(namesPointer[j]);
                        j--;
                    }
                    free(namesPointer);
                    return 0;
                }
                printf("%s\n", directoryEntry->d_name);
                strcpy(namesPointer[i], directoryEntry->d_name);
                printf("Got to 2\n");
                i++;
            }
        }
        closedir(directory);
        return numberOfNames;
    }
    free(namesPointer);
    return -1;
}

Answer 1

您分配内存，然后用 NULL 覆盖指针值：

namesPointer[i] = malloc((strlen(directoryEntry->d_name) + 1) * sizeof(char));
if (namesPointer[i] = NULL) {...

应该是

if (namesPointer[i] == NULL)

或

if (!namesPointer[i])

执行 strcpy 时出现分段错误

Segmentation fault when doing strcpy

c

malloc

strcpy