C text game segmentation fault and debugging - c

Question

I wanted to wrote a simple text game in C. The game generates random 2D position using 2 double variables in range from -10.000 to 10.000 (X, Y) as the "treasure" position. Player begins at position 0.000, 0.000. Then the game asks the player which directions to go in X and Y. After that the game needs to give the player a simple hint, if he's getting closer(right or wrong direction based on the treasure position). When the player is less than 0.050 away from treasure in any direction, the game ends and prints out the score(cycle steps).
I wrote this, but I'm getting 'Segmentation fault' and I'm also interested about how would you modify it to get it more effective and functional.
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
int main()
{
srand (time(NULL));
char *direction_x;
char *direction_y;
double direction_forward;
double direction_back;
double direction_left;
double direction_right;
double score_x;
double score_y;
double diff_x;
double diff_y;
double lastmove_x;
double lastmove_y;
int i;
double random_x = (double)rand()/RAND_MAX*20.000-10.000;
double rounded_x = (int)(random_x * 1000.0)/1000.0;
printf ( "%f\n", random_x);
printf ( "%.3f\n", rounded_x);
double random_y = (double)rand()/RAND_MAX*20.000-10.000;
double rounded_y = (int)(random_y * 1000.0)/1000.0;
printf ( "%f\n", random_y);
printf ( "%.3f\n", rounded_y);
double player_x=0.000;
double player_y=0.000;
printf("Hello freind! Let's find the hidden treasure!\n");
do{
i++;
printf("Where would you want to go? ('straight', 'back')\n");
scanf("%s", &direction_x);
if (strcmp(direction_x, "straight") == 0)
{
printf("How far?\n");
scanf("%f", &direction_forward);
player_x = player_x + direction_forward;
printf("You've walked %.3f straight!\n", direction_forward);
printf("Your current postion is: %.3f, %.3f.\n", player_x, player_y);
diff_x = random_x - player_x;
if (diff_x < random_x)
{
printf("You're closer...\n");
}
else
{
printf("Don't like this way...\n");
}
}
else if (strcmp(direction_x, "back") == 0)
{
printf("How far?\n");
scanf("%f", &direction_back);
player_x = player_x - direction_back;
printf("You've walked %.3f backwards!\n", direction_back);
printf("Your current position is: %.3f, %.3f.\n", player_x, player_y);
if (diff_x < random_x)
{
printf("You're closer...\n");
}
else
{
printf("Don't like this way...\n");
}
}
else
{
printf("Don't accept this direction...\n");
}
printf("Where now? ('left', 'right')\n");
scanf("%s", &direction_y);
if (strcmp(direction_y, "left") == 0)
{
printf("How far?\n");
scanf("%f", &direction_left);
player_y = player_y + direction_left;
printf("You've walked %.3f left!\n", direction_left);
printf("Your current position is: %.3f, %.3f.\n", player_x, player_y);
if (diff_y < random_y)
{
printf("You're closer...\n");
}
else
{
printf("Don't like this way...\n");
}
}
else if (strcmp(direction_y, "right") == 0)
{
printf("How far?\n");
scanf("%f", &direction_right);
player_y = player_y - direction_right;
printf("You've walked %.3f right!\n", direction_right);
printf("Your current position is: %.3f, %.3f.\n", player_x, player_y);
if (diff_y < random_y)
{
printf("You're closer...\n");
}
else
{
printf("Don't like this way...\n");
}
}
else
{
printf("Don't accept this direction...\n");
}
score_x = (player_x + 0.050) - random_x;
score_y = (player_y + 0.050) - random_y;
}while ((-0.050 <= score_x <= 0.050) || (-0.050 <= score_y <= 0.050));
printf("Congratulations, treasure was finally founded! Treasure position is %.3f, %.3f.\n", random_x, random_y);
printf("Score (steps taken, less is better): %d\n", i);
return 0;
}

Answer 1

I just tried to compile your code.
First: If you use scanf() you should specify "%lf" if you want to read in a double. For example:
scanf("%lf", &direction_right);
Second: Many of your variables are not initialized. The first segmentation fault will likely be thrown at the beginning of your while-loop at this line:
scanf("%s", &direction_x);
because direction_x is not initialized it stores a pointer with a random value. This means, that it is pointing to somewhere in your memory, depending on the value previously stored at the spot where direction_x was located to. This likely causes the crash.
Avoid this by declaring an array like so.
char direction_x[42];
char direction_y[42];
But don't forget to check your input lengths!
There are many more variables you use before initializing them. Check your compilerwarnings by adding the flag -Wall (if you are using gcc).
Third: Try to structure your code. anything within a if-else statement can be put into an own function. This will help you and anyone else who tries to understand your code.

Answer 2

char *direction_x; and char *direction_y; should be like char st[1024] for use in scanf
i must init before use it
scanf("%s", &direction_x); should be scanf("%s", direction_x);
For double should use %lf, not %f
-0.050 <= score_x <= 0.050 should be -0.050 <= score_x && score_x <= 0.050
and so on ...
I rewrite it.
The follow code could work:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <math.h>
int main()
{
srand (time(NULL));
double random_x = (double)rand()/RAND_MAX*20.000-10.000;
double random_y = (double)rand()/RAND_MAX*20.000-10.000;
double player_x=0.000;
double player_y=0.000;
double score_x;
double score_y;
int step = 0;
printf("Hello friend! Let's find the hidden treasure!\n");
do {
step++;
char st[1024];
double data;
printf("Where would you want to go? (horizontal or vertical)\n");
scanf("%s", st);
printf("How far?\n");
scanf("%lf", &data);
if (strcmp(st, "horizontal") == 0)
{
player_x = player_x + data;
printf("You've walked %.3f left!\n", data);
printf("Your current position is: %.3f, %.3f.\n", player_x, player_y);
if (fabs(player_x - random_x) < fabs(player_x - data - random_x))
printf("You're closer...\n");
else
printf("Don't like this way...\n");
}
else if (strcmp(st, "vertical") == 0)
{
player_y = player_y + data;
printf("You've walked %.3f down!\n", data);
printf("Your current position is: %.3f, %.3f.\n", player_x, player_y);
if (fabs(player_y - random_y) < fabs(player_y - data - random_y))
printf("You're closer...\n");
else
printf("Don't like this way...\n");
} else {
continue;
}
score_x = player_x - random_x;
score_y = player_y - random_y;
} while (fabs(score_x) > 0.050 && fabs(score_y) > 0.050);
printf("Congratulations, treasure was finally founded! Treasure position is %.3f, %.3f.\n", random_x, random_y);
printf("Score (steps taken, less is better): %d\n", step);
return 0;
}