Question

I’m getting segmentations fault while doing this, compiler does not show any error though.
Forgive me if I’m asking very basic question, because I have not been good at coding in C and its a long time.

Here is my code:

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

struct link_list {
    int x;
    int y;
    struct link_list *next;
    struct link_list *prev;
};

int inp_sum (int *x, int *y){
        printf("Enter x:");
        scanf("%d",&x);
        printf("Enter y:");
        scanf("%d",&y);
    printf("%d+%d",x,y);
    int z;
    z=*x+*y;
    return z;
}

void main(){
    struct link_list *first_node;
    first_node=malloc(sizeof(struct link_list));
    first_node->next=0;
    first_node->prev=0;

    struct link_list *cur;
    cur = malloc(sizeof(struct link_list));
    while(inp_sum(&cur->x,&cur->y)<100){
        cur->next=malloc(sizeof(struct link_list));
        cur=cur->next;
        cur->next=0;
        cur->prev=0;
    }

    print_llist(first_node);
}

print_llist(struct link_list *root){
    struct link_list *current;
    current=malloc(sizeof(struct link_list));
    current = root;
    while ( current != NULL ) {
        printf( "%d\n", current->x );
        current = current->next;
    }
}

what I want to do is create a link list node and extend the link list if sum of inputs is less than 100, for that I want to send pointers of x,y(members of node) to a function which returns their sum after taking input and storing the input to them.

But I think I’m doing this wrong while passing the pointers or adding the pointers.

Regards

Answer 1

x and y are already pointers, so this:

    printf("Enter x:");
    scanf("%d",&x);
    //         ^ address of int *
    printf("Enter y:");
    scanf("%d",&y);

        // ^ address of int *

should be:

    printf("Enter x:");
    scanf("%d",x);
    //         ^ address of int
    printf("Enter y:");
    scanf("%d",y);
    //         ^ address of int

In the code you wrote, you read into the int pointer, e.g. override the address of the int, and then dereference it (in the addition) which causes segmentation fault.