Segmentation Core dumped - c

Question

| |0|1|2|3|4|5|6|7|8|9|
|0| | | | | | | | | | |
|1| | | | | | | | | | |
|2| | | | | | | | | | |
|3| | | | | | | | | | |
|4| | | | | | | | | | |
|5| | | | | | | | | | |
|6| | | | | | | | | | |
|7| | | | | | | | | | |
|8| | | | | | | | | | |
|9| | | | | | | | | | |
I am trying to make a grid that looks like this. I currently keep getting Segmentation Fault Core dumped whenever I try to run the executable. The compiler is also not showing any errors. I am not sure how to print the numbers inside the grid either. Below is the code I currently have (just a part of the whole assignment). Any help is greatly appreciated.
void displayBoard(Cell board[BOARD_HEIGHT][BOARD_WIDTH], Player * player)
{
/* TODO */
int i,j;
char grid[BOARD_HEIGHT + 2][BOARD_WIDTH + 2];
for(i = 0; i < BOARD_HEIGHT; i++)
{
for(j = 0; j < BOARD_WIDTH; j++)
{
grid[BOARD_HEIGHT + 2][BOARD_WIDTH + 2] = '|';
printf("%c", grid[BOARD_HEIGHT + 2][BOARD_WIDTH + 2]);
printf("%s", EMPTY_OUTPUT);
}
printf("\n");
}
}
The BOARD_HEIGHT and BOARD_WIDTH are variables defined in a header file.
#ifndef BOARD_H
#define BOARD_H
#include "helpers.h"
#include "player.h"
#define BOARD_WIDTH 10
#define BOARD_HEIGHT 10
typedef enum cell
{
EMPTY,
BLOCKED,
PLAYER
} Cell;
#define EMPTY_OUTPUT " "
#define BLOCKED_OUTPUT "*"
Cell BOARD_1[BOARD_HEIGHT][BOARD_WIDTH];
Cell BOARD_2[BOARD_HEIGHT][BOARD_WIDTH];
typedef enum playerMove
{
PLAYER_MOVED,
CELL_BLOCKED,
OUTSIDE_BOUNDS
} PlayerMove;
void initialiseBoard(Cell board[BOARD_HEIGHT][BOARD_WIDTH]);
void loadBoard(Cell board[BOARD_HEIGHT][BOARD_WIDTH],
Cell boardToLoad[BOARD_HEIGHT][BOARD_WIDTH]);
Boolean placePlayer(Cell board[BOARD_HEIGHT][BOARD_WIDTH], Position position);
PlayerMove movePlayerForward(Cell board[BOARD_HEIGHT][BOARD_WIDTH],
Player * player);
void displayBoard(Cell board[BOARD_HEIGHT][BOARD_WIDTH], Player * player);
#endif
this second part is in the header file.
The full code can be found here a1

Answer 1

Your bug is on the line where you index grid beyond the end of the array:
grid[BOARD_HEIGHT + 2][BOARD_WIDTH + 2] = '|'; // Bug
This line writes beyond the end of the grid array defined locally as:
char grid[BOARD_HEIGHT + 2][BOARD_WIDTH + 2];
Note that the valid indexes into grid[][] go from 0 to BOARD_HEIGHT+1, and 0 to BOARD_WIDTH+1. Your code is accessible one past this in both dimensions.
This results in corrupting the stack, so when the displayBoard function returns, it has corrupted the stack and you get a segmentation fault. Removing this line eliminates the seg fault, but the code still needs work for function correctly.
You should reference the board array, and use indexes i and j, not hardcoded constants.
Here is a working version where I index into the board array, store the current cell value in currentCell, then display it based on a switch statement. This produces the following output given an empty board filled with zeroes:
scott> gcc -g -ogeraldTest -O0 board.c
scott> geraldTest
| |0|1|2|3|4|5|6|7|8|9|
|0| | | | | | | | | | |
|1| | | | | | | | | | |
|2| | | | | | | | | | |
|3| | | | | | | | | | |
|4| | | | | | | | | | |
|5| | | | | | | | | | |
|6| | | | | | | | | | |
|7| | | | | | | | | | |
|8| | | | | | | | | | |
|9| | | | | | | | | | |
Here is the code for main() and printBoard, both in board.c. Note that printBoard is passed the board by value, but it would be better to pass it by reference.
#include <stdio.h>
#include "board.h"
void displayBoard(Cell board[BOARD_HEIGHT][BOARD_WIDTH], Player * player)
{
int i,j;
// First display the header at the top.
printf("| |");
for(j=0; j<BOARD_WIDTH;j++)
printf("%d|",j);
printf("\n");
for(i = 0; i < BOARD_HEIGHT; i++)
{
// Display each row number
printf("|%d|",i);
for(j = 0; j < BOARD_WIDTH; j++)
{
// Bug: grid[BOARD_HEIGHT + 2][BOARD_WIDTH + 2] = '|';
Cell currentCell = board[i][j];
switch(currentCell) {
case BLOCKED:
printf("%s",BLOCKED_OUTPUT);
break;
case PLAYER:
printf("P");
break;
default:
printf("%s",EMPTY_OUTPUT);
break;
}
printf("|");
// This code is wrong
// printf("%c|", grid[BOARD_HEIGHT + 2][BOARD_WIDTH + 2]);
// printf("%s", EMPTY_OUTPUT);
}
printf("\n");
}
}
int main(int argc, char ** argv)
{
Cell myBoard[BOARD_HEIGHT][BOARD_WIDTH] = {0};
Player bob = 0;
displayBoard(myBoard, &bob);
}
I took your board.h and defined the missing types in order to get it to compile. You can likely just use your own headers as is.
#ifndef BOARD_H
#define BOARD_H
// #include "helpers.h"
// #include "player.h"
#define BOARD_WIDTH 10
#define BOARD_HEIGHT 10
typedef int Boolean; // Added
typedef int Player; // Added
typedef struct { // Added
int row;
int col;
} Position;
typedef enum cell
{
EMPTY,
BLOCKED,
PLAYER
} Cell;
#define EMPTY_OUTPUT " "
#define BLOCKED_OUTPUT "*"
Cell BOARD_1[BOARD_HEIGHT][BOARD_WIDTH];
Cell BOARD_2[BOARD_HEIGHT][BOARD_WIDTH];
typedef enum playerMove
{
PLAYER_MOVED,
CELL_BLOCKED,
OUTSIDE_BOUNDS
} PlayerMove;
void initialiseBoard(Cell board[BOARD_HEIGHT][BOARD_WIDTH]);
void loadBoard(Cell board[BOARD_HEIGHT][BOARD_WIDTH],
Cell boardToLoad[BOARD_HEIGHT][BOARD_WIDTH]);
Boolean placePlayer(Cell board[BOARD_HEIGHT][BOARD_WIDTH], Position position);
PlayerMove movePlayerForward(Cell board[BOARD_HEIGHT][BOARD_WIDTH],
Player * player);
void displayBoard(Cell board[BOARD_HEIGHT][BOARD_WIDTH], Player * player);
#endif