Why am I getting a segmentation fault in my code?

Question

When I compile my code with GCC and then I run it, when I call my function into my code, it prints out: "Segmentation fault (core dumped)".

I tried searching on google for solutions.

Here is my current code:

char ** saveLevelPositions() {
  int x, y;
  char ** positions;
  positions = malloc(sizeof(char *) * 25);

  for (y = 0; y < 25; y++) {
    positions[y] = malloc(sizeof(char) * 100);

    for (x = 0; x < 100; x++) {
      positions[x][y] = mvinch(y, x);
    }
  }

  return positions;
}

I expected the function to just run properly and it just gives a segmentation error.

EDIT: For a little bit of context, here is a link to the GitHub project: https://github.com/xslendix/rogue

That isn't a valid solution sadly, I tried it and I got the same problem. — Slendi, Apr 05 '19 at 17:36
It is definitely a valid part of a solution. If you still have a problem, then it is not in the posted code (`mvinch`)?. — Eugene Sh., Apr 05 '19 at 17:36
See [How to create a Minimal, Complete, and Verifiable example](https://stackoverflow.com/help/mcve). Also a debugger might be of some help. — sjsam, Apr 05 '19 at 17:39
In your code on github I see `Room ** rooms; rooms = malloc(sizeof(Room) * 2);` - this is definitely wrong. Why `rooms` is double pointer? I haven't looked further, but I assume there might be other issues. — Eugene Sh., Apr 05 '19 at 17:55

Paul Ogilvie · Accepted Answer · 2019-04-05T18:08:34.963

As other answers and comments indicated, you should swap your use of x and y, so
positions[x][y] should be positions[y][x].

Also, you are not using the correct type to store the result of mvinch. In curses.h it says:

typedef unsigned long chtype;

so you should allocate memory as follows:

chtype ** positions;
positions = malloc(sizeof(chtype *) * 25);
positions[y] = malloc(sizeof(chtype) * 100);

And turn warnings of your compiler on, because the compiler should have flagged this error.

Why am I getting a segmentation fault in my code?

1 Answers1