free() causes SEG fault C - c

Question

int ** ARR;
int LENGTH = 1;
int DEPTH = 1;
void loadt(int ** terr)
{
terr = (int**)malloc(sizeof(int*) * (LENGTH + 1));
int i, j;
for(i = 1; i <= LENGTH; i++)
terr[i] = (int*)malloc(sizeof(int) * (DEPTH + 1));
for(i = 1; i <= LENGTH; i++)
for(j = 1; j <= DEPTH; j++)
scanf("%d", &terr[i][j]);
}
void freet(int ** terr)
{
int i;
for(i = 1; i <= LENGTH; i++){
free(terr[i]);
}
free(terr);
}
int main(int argc, char* argv[])
{
loadt(ARR);
freet(ARR);
return 0;
}
Hello. I probably miss sth really basic here but after I run the program it crashes."Segmentation fault (core dumped)" Why?

Answer 1

Because in c arguments to functions are always passed by value, so your unecessarily global variable is not getting reassigned inside the function since you are passing it as a parameter and hence a copy of it is made, which is the one that is actually reassigned.
So you are calling free() on an uninitialized poitner.
Try like this
int **loadt(int LENGTH, int DEPTH)
{
int **terr;
int i, j;
terr = malloc(sizeof(int*) * (LENGTH + 1));
if (terr == NULL)
return NULL;
for (i = 1; i <= LENGTH; i++) {
terr[i] = malloc(sizeof(int) * (DEPTH + 1));
if (terr[i] == NULL) {
for (j = i ; j >= 0 ; --j) {
free(terr[j]);
}
free(terr);
return NULL;
}
}
for (i = 1; i <= LENGTH; i++) {
for (j = 1; j <= DEPTH; j++) {
scanf("%d", &terr[i][j]);
}
}
return terr;
}
void freet(int **terr)
{
int i;
if (terr == NULL)
return; // `free()' also accepts NULL pointers
for (i = 1; i <= LENGTH; i++) {
free(terr[i]);
}
free(terr);
}
int main(int argc, char* argv[])
{
int **ARR;
int LENGTH = 1;
int DEPTH = 1;
ARR = loadt(LENGTH, DEPTH);
freet(ARR);
return 0;
}
Another problem, is that you start your loops at i = 1, which is fine because you are allocating enough space, but it's not the way you should do it. Instead for (i = 0 ; i < LENGTH ; ++i) would be how a c programmer would do it. Note that you are wasting the first element of your array.