Can't get the reason for segfault

Question

EDIT : Note that It's not that I can't access the memory allocated by storeContents() in main() if you think so. Program crashes during the execution of storeContents()

The program fails here :

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

It's strcpy() not the printf(), I added it just for the reference.

The debugger(gdb) says :

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

I am making a program that involves the following function "storeContents"(It stores contents' names of a directory in a dynamic array). There are two issues with this function : (1) It says "Stored file_name" twice for the first file and (2) says "Segmentation fault". I can't figure out either of them. Thanks for your efforts!

#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

contents in the function storeContents is a local copy of contents from main.

Changing it in the function does not change the variable in main.

You should return the array. Change
static void storeContents(struct dirent *dir, DIR *dirp, char **contents, unsigned numOfContents);
to
static char **storeContents(struct dirent *dir, DIR *dirp, unsigned numOfContents);

,return contents; in the function and call it like char **contents = storeContents(...);

Answer 2

Some bugs:

• contents is a local parameter to the function, it will not get returned to main(). See Dynamic memory access only works inside function.
• contents = (char **)malloc(numOfContents); is wrong, you need to allocate room for numOfContents pointers. Change this to contents = malloc(numOfContents * sizeof(*contents)).
• You should check each call to readdir and make sure it doesn't return NULL.