Failing to assign memory to a pointer of a pointer - c

Question

My problem is that it fails to assign memory to a (char*) pointer and I can't seem to understand why.
I reviewed other similar questions, but I can't seem to grasp the answer.
I'm trying to return a list of strings, but I know that in C I can't return char**, but I can do that via the char** parameter. My attempt is in the code snippets below.
in a.c
void list(char** fileList) {
int fileIndex = 0;
fileList = (char**)malloc(DIRECTORY_SIZE * sizeof(char*));
while ((dir = readdir(currentDirectory)) != NULL)
{
fileList[fileIndex] = (char*)malloc(FILENAME_LENGTH * sizeof(char)); //It fails here
fileList[fileIndex] = strncpy(fileList[fileIndex], dir->d_name, FILENAME_LENGTH);
fileIndex++;
printf("%s\n", fileList[fileIndex]);
}
}
in main.c
int main() {
char** fileList;
list(fileList);
for(int i = 0; i < 10; i++) {
printf("%s\n", fileList[i]);
}
}
I already looked over these questions:
Assigning memory to double pointer?
segment fault, assigning to double pointer in c
Assigning memory to double pointer?

Answer 1

What happens is that the memory pointer fileList gets copied to the list function, when the list function then changes the pointer, but the initial pointer wouldn't change.
To fix this you could give it a pointer to the pointer to change the actual pointer value, like this:
void list(char*** fileList) {
int fileIndex = 0;
*fileList = (char**)malloc(DIRECTORY_SIZE * sizeof(char*));
while ((dir = readdir(currentDirectory)) != NULL)
{
*fileList[fileIndex] = (char*)malloc(FILENAME_LENGTH * sizeof(char)); //It fails here
*fileList[fileIndex] = strncpy(fileList[fileIndex], dir->d_name, FILENAME_LENGTH);
fileIndex++;
printf("%s\n", fileList[fileIndex]);
}
}
int main() {
char** fileList;
list(&fileList);
for(int i = 0; i < 10; i++) {
printf("%s\n", fileList[i]);
}
}
But I personally find this a bit clunky, so it would be better to do it like this:
char** list(void) {
char** fileList;
int fileIndex = 0;
fileList = (char**)malloc(DIRECTORY_SIZE * sizeof(char*));
while ((dir = readdir(currentDirectory)) != NULL)
{
fileList[fileIndex] = (char*)malloc(FILENAME_LENGTH * sizeof(char)); //It fails here
fileList[fileIndex] = strncpy(fileList[fileIndex], dir->d_name, FILENAME_LENGTH);
fileIndex++;
printf("%s\n", fileList[fileIndex]);
}
return filelist;
}
int main() {
char** fileList = list();
for(int i = 0; i < 10; i++) {
printf("%s\n", fileList[i]);
}
}