Why this code resulted a segmentation fault? - c

Question

i am writing a simple simulator of spilling eggs in а pan with the flood fill algorithm in C. So the pan is a char matrix, and with '#' are his walls,'.' means that the place is empty and 'O' that it has a egg that will spill.
That is an example of what that program should do.
10 10
..##......
.#O.#.....
.#..#..#..
..##..#.#.
.......#..
..#####...
..#...#...
..#...##..
...##..#..
....####..
⇨
..##......
.#OO#.....
.#OO#..#..
..##..#.#.
.......#..
..#####...
..#***#...
..#***##..
...##**#..
....####..
i have written that:
#include <stdio.h>
void food_fill(int,int,char [1000][1000],int,int,char);
int main(){
int row,col,rows,cols;
scanf("%d %d",&rows,&cols);
getchar();
char matrix [rows][cols];
for(row = 0;row < rows;row++){
for(col = 0;col < cols;col++){
scanf("%c",&matrix[row][col]);
}
getchar();
}
int foodX=0,foodY=0;
char foodChar='s';
for(row=0;row<rows;row++){
for(col = 0;col < cols;col++){
if(matrix[row][col] == 'O'){
foodX = row;
foodY = col;
foodChar = matrix[row][col];
}
}
}
food_fill(rows,cols,matrix,foodX,foodY,foodChar);
for(row = 0;row < rows;row++){
for(col = 0;col <cols;col++){
printf("%c",matrix[row][col]);
}
printf("\n");
}
return 0;
}
void food_fill(int rows,int cols,char matrix[rows][cols],int foodX,int foodY,char foodChar){
int r=rows,c=cols;
if(matrix[foodX][foodY] == '#')return;
if(foodX < 0 || foodX >= rows || foodY < 0 || foodY >= cols)return;
matrix[foodX][foodY] = foodChar;
food_fill(r,c,matrix,foodX+1,foodY,foodChar);
food_fill(r,c,matrix,foodX-1,foodY,foodChar);
food_fill(r,c,matrix,foodX,foodY+1,foodChar);
food_fill(r,c,matrix,foodX,foodY-1,foodChar);
}
It is not completed yet but the food_fill() function resulted in segmentation fault and i don't know why.

Answer 1

if(matrix[foodX][foodY] == '#')return;
if(foodX < 0 || foodX >= rows || foodY < 0 || foodY >= cols)return;
Order is wrong. As a result you are accessing invalid indices. Giving you segmentation fault. Correct one would be
if(foodX < 0 || foodX >= rows || foodY < 0 || foodY >= cols)return;
if(matrix[foodX][foodY] == '#')return;
Also there are bugs on many levels.
You are having an infinite loop due to repetitive similar calls.
int dx[]={1,0,-1,0};
int dy[]={0,1,0,-1};
void food_fill(int rows,int cols,char matrix[][cols],int foodX,int foodY,char foodChar){
matrix[foodX][foodY] = foodChar;
for(int i=0;i<4;i++){
if( foodX+dx[i]>=0 && foodX+dx[i]<rows && foodY+dy[i] >=0 && foodY+dy[i]<cols && matrix[foodX+dx[i]][foodY+dy[i]] != '#' && matrix[foodX+dx[i]][foodY+dy[i]]!=foodChar){
food_fill(rows,cols,matrix,foodX+dx[i],foodY+dy[i],foodChar);
}
}
}
The main condition change is
if( foodX+dx[i]>=0 && foodX+dx[i]<rows && foodY+dy[i] >=0 && foodY+dy[i]<cols && matrix[foodX+dx[i]][foodY+dy[i]] != '#' && matrix[foodX+dx[i]][foodY+dy[i]]!=foodChar){