linked lists and stacks and a segmentation fault [closed] - c

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First time posting a question on stack overflow so be nice.
I'm trying to write a program for school. This program is suppose to take a data set and turn it into a maze. The error I'm getting is a segmentation fault in putty but not in the IDE I'm using. Not sure what to do or how to handle it. I tried putting printf statements everywhere but none of them really show up doesnt make sense. Maybe because the functions themselves cause the fault not sure though what part.
//CODE BEGINS****************************************************************
#include <stdio.h>
#include <stdlib.h>
typedef int bool;
#define FALSE 0
#define TRUE 1
typedef struct mazeStruct
{
char **arr; /* allows for a dynamic 2-D maze of any size */
int xsize, ysize;
int xstart, ystart;
int xend, yend;
bool end;
} maze;
struct linkedStruct
{
int x;
int y;
bool Unvisited;
struct linkedStruct* next;
};
typedef struct linkedStruct linked;
typedef linked* linkedPtr;
void push(linkedPtr* hd, int Xval, int Yval)
{
linkedPtr ptr = (linkedPtr) malloc(sizeof(linked));
ptr->x = Xval;
ptr->y = Yval;
ptr->Unvisited = FALSE;
ptr->next = *hd;
*hd = ptr;
}
int isEmpty(linkedPtr hd)
{
if (hd == NULL)
return TRUE;
else
return FALSE;
}
int top(linkedPtr hd)
{
return (hd->x && hd->y);
}
void pop(linkedPtr* hd)
{
linkedPtr ptr = (linkedPtr) malloc(sizeof(linked));
ptr->x = NULL;
ptr->y = NULL;
ptr->Unvisited = TRUE;
ptr->next = *hd;
*hd = ptr;
free(ptr);
}
int main(int argc, char **argv)
{
maze m1;
linkedPtr head = NULL;
int xpos, ypos;
int i, j;
m1.end = FALSE;
FILE *src;
//FILE *src = fopen ("mazeData1.txt",'r');
/* verify the proper number of command line arguments were given */
if (argc != 2)
{
printf("Usage: %s <input file name>\n", argv[0]);
exit(-1);
}
/* Try to open the input file. */
if ((src = fopen(argv[1], "r")) == NULL)
{
printf("Can't open input file: %s", argv[1]);
printf("Standard Error.\n");
exit(-1);
}
/* read in the size, starting and ending positions in the maze */
fscanf(src, "%d %d", &m1.xsize, &m1.ysize);
if (m1.xsize < 1 || m1.ysize < 1)
{
printf("Size has to be 1 or above.\n");
fscanf(src, "%d %d", &m1.xsize, &m1.ysize);
}
fscanf(src, "%d %d", &m1.xstart, &m1.ystart);
if (m1.xstart > m1.xsize || m1.ystart > m1.ysize || m1.xstart < 1
|| m1.ystart < 1)
{
printf("The start has to be within the maze.\n");
fscanf(src, "%d %d", &m1.xstart, &m1.ystart);
}
fscanf(src, "%d %d", &m1.xend, &m1.yend);
if (m1.xend > m1.xsize || m1.yend > m1.ysize || m1.xend < 1 || m1.yend < 1)
{
printf("The end has to be within the maze.\n");
fscanf(src, "%d %d", &m1.xend, &m1.yend);
}
if (m1.xend == NULL || m1.yend == NULL)
{
printf("Error: Need at least three lines of input");
exit(-1);
}
/* print them out to verify the input */
printf("size: %d, %d\n", m1.xsize, m1.ysize);
printf("start: %d, %d\n", m1.xstart, m1.ystart);
printf("end: %d, %d\n", m1.xend, m1.yend);
/* allocate the maze */
m1.arr = (char **) malloc(sizeof(char *) * (m1.xsize + 2));
for (i = 0; i < m1.xsize + 2; i++)
m1.arr[i] = (char *) malloc(sizeof(char) * (m1.ysize + 2));
/* initialize the maze to empty */
for (i = 0; i < m1.xsize + 2; i++)
for (j = 0; j < m1.ysize + 2; j++)
m1.arr[i][j] = '.';
/* mark the borders of the maze with *'s */
for (i = 0; i < m1.xsize + 2; i++)
{
m1.arr[i][0] = '*';
m1.arr[i][m1.ysize + 1] = '*';
}
for (i = 0; i < m1.ysize + 2; i++)
{
m1.arr[0][i] = '*';
m1.arr[m1.xsize + 1][i] = '*';
}
/* mark the starting and ending positions in the maze */
m1.arr[m1.xstart][m1.ystart] = 's';
m1.arr[m1.xend][m1.yend] = 'e';
/* mark the blocked positions in the maze with *'s */
while (fscanf(src, "%d %d", &xpos, &ypos) != EOF)
{
if (xpos > m1.xsize || ypos > m1.ysize || xpos < 1 || ypos < 1
|| (xpos == m1.xstart && ypos == m1.ystart)
|| (xpos == m1.xend && ypos == m1.yend))
{
printf(
"Error: X or Y is: out of range or is on the end or is on the start\n");
continue;
}
m1.arr[xpos][ypos] = '*';
}
/* print out the initial maze */
for (i = 0; i < m1.xsize + 2; i++)
{
for (j = 0; j < m1.ysize + 2; j++)
printf("%c", m1.arr[i][j]);
printf("\n");
}
// THE START OF THE DEPTH FIRST SEARCH METHOD
for (i = 0; i < m1.xsize + 2; i++)
{
for (j = 0; j < m1.ysize + 2; j++)
{
if (m1.arr[i][j] != '*')
{
head->Unvisited = FALSE;
head->next = head->next + 1; //MAYBE
}
}
}
head->x = m1.xstart;
head->y = m1.ystart;
head->Unvisited = FALSE;
while ((isEmpty(head) == FALSE) && (m1.end == FALSE))
{
if ((m1.xend == head->x) && (m1.yend == head->y))
{
printf("The END has be found!\n");
m1.end = TRUE;
}
if ((head->x + 1 && head->y) == TRUE)
{
push(&head, head->x + 1, head->y);
}
else if ((head->x - 1 && head->y) == TRUE)
{
push(&head, head->x - 1, head->y);
}
else if ((head->x && head->y + 1) == TRUE)
{
push(&head, head->x, head->y + 1);
}
else if ((head->x && head->y) == TRUE)
{
push(&head, head->x, head->y - 1);
}
else
{
pop(head);
}
}
if (isEmpty(head) == TRUE)
{
printf("Maze has no solution");
exit(0);
}
else
{
printf("%d %d", &head);
}
printf("%d", top(head));
free(m1.arr);
m1.arr = NULL;
return 1;
}

Answer 1

The main problem here is that you are hiding pointer with typedef:
typedef linked* linkedPtr;
In main you are declaring
linkedPtr head = NULL;
but you never allocate/mallocate space for that variable and the first piece of code that dereference it invokes Undefined Behavior because you are dereferencing a null pointer
// THE START OF THE DEPTH FIRST SEARCH METHOD
for (i = 0; i < m1.xsize + 2; i++)
{
for (j = 0; j < m1.ysize + 2; j++)
{
if (m1.arr[i][j] != '*')
{
head->Unvisited = FALSE; <----------BOOOOOOOOOOOOOOM-------
head->next = head->next + 1;
}
}
}
Moreover you have a type mismatch calling pop function, change
pop(head);
to
pop(&head);