Question

I am trying to allocate and print a 2d array in C and my methods seem to work but I get a segmentation fault when printing my array. Any ideas?

#include <stdio.h>
#include<stdlib.h>

#define WALL 1;
#define EMPTY 0;

int rows;
int columns;

int startRow, startCol;

void getPuzzleParams();
void printMaze();
int solve(char** puzzle, int, int);
void findStartAndEnd(char** puzzle);

main() {
getPuzzleParams();

char **puzzle;
puzzle = (char **)malloc(sizeof(char *)*rows);
int y;
for(y = 0; y < rows;y++)
    puzzle[y] = (char *)malloc(sizeof(char)*columns);

FILE *fptr;
char c;
char file_name[20];
int i,j;

printf("Type in the name of the file containing the Field\n");
scanf("%s",file_name);
fptr=fopen(file_name,"r");
for (i=0; i<rows; i++)
    for (j=0; j<columns; j++){
        c=fgetc(fptr); 
        while ( !((c == '1')||(c =='0')) ) c=fgetc(fptr);
        puzzle[i][j]=c;
    }
fclose(fptr);

for (i=0; i<rows; i++) {
    for (j=0; j<columns; j++)  {
        if (j == 0) printf("\n");                
        printf("%c  ",puzzle[i][j]);
    }
}
printf("\n");

printf("print");
//printMaze(puzzle);
printf("find");
findStartAndEnd(puzzle);
printMaze(puzzle);
solve(puzzle, 1, 2);
}

void getPuzzleParams() {
printf("Enter the dimensions of the puzzle which need to be between 5 and 100\n");
printf("Enter the desired number of Rows: ");
scanf("%d", &rows); 
printf("Enter the desired number of Columns: ");
scanf("%d", &columns);
printf("Rows: %d, Columns: %d\n", rows, columns);
if(rows > 100 || rows < 5 || columns > 100 || columns < 5) {
    getPuzzleParams();
}

}

void printMaze(char** puzzle) {
int i,j;
for (i=0; i<rows; i++)
    for (j=0; j<columns; j++)  {
        if (j == 0) printf("\n");                
        printf("%c  ",puzzle[i][j]);
    }
printf("\n");
printf("sdfsdF");
}

void findStartAndEnd(char** puzzle) {
int foundEnterence = 0;
int i;
printf("start");
for(i = 0; i < columns; i++) {
    printf("top row");
    if(puzzle[0][i]=='0') {
        if(!foundEnterence) {
            foundEnterence = 1;
            startRow = 0;
            startCol = i;
            puzzle[0][i] = 'S';
        } else {
            puzzle[0][i] = 'G';
        }
    }
}
for(i = 0; i < rows; i++) {
    if(puzzle[i][rows]=='0') {
        if(!foundEnterence) {
            foundEnterence = 1;
            startRow = i;
            startCol = rows;
            puzzle[i][rows] = 'S';
        } else {
            puzzle[i][rows] = 'G';
        }
    }
}
for(i = columns; i >= 0; i--) {
    if(puzzle[rows][i]=='0') {
        if(!foundEnterence) {
            foundEnterence = 1;
            startRow = rows;
            startCol = i;
            puzzle[rows][i] = 'S';
        } else {
            puzzle[rows][i] = 'G';
        }
    }
}
for(i = rows; i >= 0; i++) {
    if(puzzle[i][0]=='0') {
        if(!foundEnterence) {
            foundEnterence = 1;
            startRow = i;
            startCol = 0;
            puzzle[i][0] = 'S';
        } else {
            puzzle[i][0] = 'G';
        }
    }
}
}

int solve(char** puzzle, int x, int y) {
printf("%c",puzzle[x][y]);

}

It may be a problem with an improper use of malloc, but I’ve tried a few different initializations with no success.

Edit: The comand line output is:

Enter the dimensions of the puzzle which need to be between 5 and 100
Enter the desired number of Rows: 12
Enter the desired number of Columns: 10
Rows: 12, Columns: 10
Type in the name of the file containing the Field
maze.txt

1  1  1  1  1  1  1  0  1  1  
1  1  0  0  1  0  0  0  0  1  
1  0  0  0  1  0  0  1  1  1  
1  0  0  0  0  0  0  0  0  1  
1  0  1  0  0  1  0  1  1  0  
1  1  0  0  0  1  0  1  1  1  
1  1  0  1  1  0  0  0  0  1  
1  0  1  0  0  1  0  1  0  1  
1  1  1  0  1  0  1  0  1  1  
1  0  0  1  0  1  0  0  0  1  
1  0  0  0  1  1  1  0  1  1  
1  1  1  1  1  1  1  1  1  1  
Segmentation fault

Answer 1

You’re crashing in code you haven’t pasted. The print completes without error. As you can see, the entire maze has been printed. You aren’t seeing print or find because they’re in the output buffer which you haven’t flushed — you’re crashing before your code gets a chance to flush it.

Use a good debugger to see where the fault is occurring.