Thread: Segmentation Fault

Can someone help me figure out why I am getting a seg fault at run time...

Code:

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


int main(void){
printf("Cake");/*debugging, didnt even reach this statement*/
int data_in[10];
FILE *pfile;
pfile = fopen("input.txt", "r");
int i,k,num;

     do{
	fscanf(pfile,"%d",&num);
	data_in[i] = num;
	i++;
	}while(pfile!=NULL);

for(k=0; k<=10;k++){
	printf("%d",data_in[k]);

}

return 0;

}

I have no other function in the program. I broke up all of my declarations and initialized all the variables to zero, but the seg fault is still there...

Originally Posted by bigparker

I have no other function in the program. I broke up all of my declarations and initialized all the variables to zero, but the seg fault is still there...

Originally Posted by quzah

The real problem is that i is used uninitialized.

Quzah.

<echo> And did you make sure you didn't go over with k? (Hint: you went over with k.)

Code:

int main(){
printf("Cake");
int data_in[100];
FILE *pfile;
pfile = fopen("input.txt", "r");
int i=0;
int k=0;
int num=0;

     do{
	fscanf(pfile,"%d",&num);
	data_in[i] = num;
	i++;
	}while(pfile!=NULL);

for(k=0; k<=10;k++){
	printf("%d",data_in[k]);

}

return 0;

}

after initializing "i" I still get the seg fault at run time...

Originally Posted by bigparker

Code:

int main(){
printf("Cake");
int data_in[100];
FILE *pfile;
pfile = fopen("input.txt", "r");
int i=0;
int k=0;
int num=0;

     do{
	fscanf(pfile,"%d",&num);
	data_in[i] = num;
	i++;
	}while(pfile!=NULL);

for(k=0; k<=10;k++){
	printf("%d",data_in[k]);

}

return 0;

}

after initializing "i" I still get the seg fault at run time...

<echo> And did you make sure you didn't go over with k? (Hint: you went over with k.)

Code:

int main(){
printf("Cake");
int data_in[100];
FILE *pfile;
pfile = fopen("input.txt", "r");
int i=0;

int num=0;

     do{
	fscanf(pfile,"%d",&num);
	data_in[i] = num;
	i++;
	}while(pfile!=NULL);


	printf("%d",data_in[0]);



return 0;

}

I removed the for-loop and i just have print statement to print the value at data_in[0]...and the seg fault is still there. I cant seem to figure it out...

Not to seem basic, but how do i test to be sure that i dont run past the end of my buffer?

Try following the value of pfile.

thanks...that got rid of the seg fault. Do you guys have any idea of why the the program would only print the last value in my input file? its prints 421 repeatedly...

Code:

# define MAX 1000
#include <stdio.h>
#include <stdlib.h>


int main(){
printf("Cake");
int data_in[MAX];
FILE *pfile;
pfile = fopen("input.txt", "r");
int i=0;
int k=0;
int num=0;

     do{
	fscanf(pfile,"%d",&num);
	data_in[i] = num;
	i++;
	}while((pfile!=NULL)&& (i<MAX));

	for(k=0; k<MAX; k++){
	printf("%d\n",data_in[k]);
	}


return 0;

}

my input file looks like this:

Code:

383
886
777
915
793
335
386
492
649
421

oh ok...I got that straight...it was because I had MAX set to a value greater than the number of integers in my input file...

Your program prints the ten numbers in the file, and then the last number an extra 990 times. You need to keep track of how many numbers get read from the file -- I think you think pfile is going to become NULL at end of file? It doesn't.