Roguelike dungeon generator segfaults, compiles fine

[kidko]

Hi, I'm in the process of writing a roguelike (ex Nethack). It's not big, but should still be playable. I've gotten to level generation, and am basically just 'carving' the rooms out of a blank slate.

The entire floor starts off as an array of rock (0x00), with passable rooms/hallways being open space (0x01). Basically, mapgen::createM ap() generates a room and hallway MAXROOMS times. It makes sure that nothing overlaps or goes out of the bounds of the array (which is MAXX by MAXY). It compiles fine, but as soon as I call createMap, it spouts the error "Segmentati on fault (core dumped)". Does anybody have any ideas as to what is going wrong?

I'm compiling using g++ 1.4.2 (Ubuntu).

#ifndef MAPGEN_H
#define MAPGEN_H

#include "dice.h"
// Has the header with rand() in it... just the library version

namespace mapgen {

	const int MAXX = 80; // Change to change map sizes
	const int MAXY = 22; // " "
	const int MAXROOMS = 6;
	const int MAXROOMX = 5;
	const int MAXROOMY = 5;
	const int MAXHALLLENGTH = 10;

	int map[MAXX][MAXY]; // Initialize map
	
	int makeHall(int atx, int aty, int dir) {
		// Directions:
		//    1
		// 2     0
		//    3

		int length = (rand() % MAXHALLLENGTH) + 1;
		

		bool clean = true;
		// Checks for size
		if ((length + atx) > MAXX || (atx - length) < 0 || (aty - length) < 0 || (length + aty) > MAXY) {
			clean = false;
		}

		if (clean) {
	
			if (dir == 0) {
				// East
				for (int i = atx; i <= length; i++) {
					map[i][aty] = 0x01;
				}
			} else if (dir == 1) {
				// North
				for (int i = aty; i <= length; i--) {
					map[atx][i] = 0x01;
				}
			} else if (dir == 2) {
				// West
				for (int i = atx; i <= length; i--) {
					map[i][aty] = 0x01;
				}
			} else {
				// South
				for (int i = aty; i <= length; i++) {
					map[atx][i] = 0x01;
				}
			}
		}	
	
	return 0;	

	}
	
	void makeRoom() {
		int xa, xb, ya, yb; // Rectangle Coords:
        /* (xa, ya) +---------+
 *                  |         |
 *                  |         |
 *                  +---------+ (xb, yb)
 		*/
		int height, width; // For calcs...
		
		height = (rand() % MAXROOMY) + 1;
		width = (rand() % MAXROOMX) + 1;
		
		xa = rand() % MAXX;
		ya = rand() % MAXY;
		xb = xa + width;
		yb = ya + height;

		bool clean = true;

		// Check to make sure area of room is clear
		if (map[xa][ya] != 0x00 || map[xb][yb] != 0x00) {
			clean = false;
		}
		// Check to make sure it's in the grid...
		if (xb > MAXX || yb > MAXY) {
			clean = false;
		}
		
		if (clean) {

			for (int i = xa; i <= xb; i++) {
				for (int j = ya; j <= yb; j++) {
					map[i][j] = 0x01; // Floor ('.')
				}
			}
	
			int hx;
			int hy;

			int wall = (rand() % 4);
			if (wall == 0) {
				// East
				hx = xb;
				hy = (ya + (rand() % (yb - 1)) + 1);
			} else if (wall == 1) {
				// North
				hx = (xa + (rand() % (xb - 1)) + 1);
				hy = ya;
			} else if (wall == 2) {
				// West
				hx = xa;
				hy = (ya + (rand() % (yb - 1)) + 1);
			} else {
				// South
				hx = (xa + (rand() % (xb - 1)) + 1);
				hy = yb;
			}

			makeHall(hx,hy,wall);
		}
	}


	void createMap() {
                for (int i = 0; i < MAXX; i++) {
                        for (int j = 0; j < MAXY; i++) {
                                map[i][j] = 0x00;
                        }
                }
                for (int i = 0; i <= MAXROOMS; i++) {
                        makeRoom();
                }
        }

}

#endif

[RRick]

Seg faults usually mean you are trying to access an illegal address like 0x0, or 0x01 or something like that.

Instead of trying to solve the problem by looking at the code, let the debugger (i.e. gdb or ddd) or memory checker (i.e. valgrind) tell you what is happening.

The debugger is especially good at stopping at seg fault conditions and then you can inspect the vlaues in the variables right there. To turn on the debugging, add "-g -O0" flags to your compilation.

[kidko]

GDB helped a lot. It located the segfault: mapgen.h: 127 (newline) map[i][j] = 0x00;

So, is my code trying to reference the memory at 0x00? And if it is, I should be using decimal for symbols instead of hex?

Seg faults usually mean you are trying to access an illegal address like 0x0, or 0x01 or something like that.

Instead of trying to solve the problem by looking at the code, let the debugger (i.e. gdb or ddd) or memory checker (i.e. valgrind) tell you what is happening.

The debugger is especially good at stopping at seg fault conditions and then you can inspect the vlaues in the variables right there. To turn on the debugging, add "-g -O0" flags to your compilation.

[kidko]

Sorry to double post, but it won't let me edit any more.

I recompiled after changing all 0x00s to 0s, 0x01s to 1s, etc., and again included -g -O0 in my g++ flags. When I ran it through gdb, it isolated the segfault at the same point. What's wrong with this code? (Snipped to what I think plays a part):
[code="cpp"]
namespace mapgen {

const int MAXX = 80; // Change to change map sizes
const int MAXY = 22; // " "

int map[MAXX][MAXY]; // Initialize map

void createMap() {
for (int i = 0; i < MAXX; i++) {
for (int j = 0; j < MAXY; i++) {
map[i][j] = 0; // SEGFAULT HERE
}
}
for (int i = 0; i <= MAXROOMS; i++) {
makeRoom();
}
}

}[/code]

[weaknessforcats]

namespace mapgen {

const int MAXX = 80; // Change to change map sizes
const int MAXY = 22; // " "

int map[MAXX][MAXY]; // Initialize map

void createMap() {
for (int i = 0; i < MAXX; i++) {
for (int j = 0; j < MAXY; i++) { <<<<Maybe j++ >????
map[i][j] = 0; // SEGFAULT HERE
}
}
for (int i = 0; i <= MAXROOMS; i++) {
makeRoom();
}
}

}

It looks like you have an error in your loop.

[RRick]

I can't see what is causing the seg fault in that part of the code. From the debugger, take a look at the address of map at different places (like main and you subroutine). If that has been corrupted (somehow), then it could causing the problems. Also, try setting a break point just before the crash and then step through the code. This might give you an idea of what is happening.

Corrupted addresses could be from mixing different versions of source code during the linking stage. If the corruption happens at runtime, then valgrind is the way to go. Be sure to use the memcheck option. In fact, I would try valgrind anyway. Its a second opinion and might point out the problem.

[kidko]

It looks like you have an error in your loop.

I can't believe I didn't catch that. It works fine now.

Thank you!

[RRick]

So enlighten us (actually me) with what it was. I still don't see it.

[Studlyami]

in his 2nd loop he used a i++ instead of a j++ (look at weakness post, he put a comment next to the line that caused the problem. I over-looked it too, untill weakness put up the comment.