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ERROR: segmentation fault (core dumped)

This is a discussion on ERROR: segmentation fault (core dumped) within the C Programming forums, part of the General Programming Boards category; when i am trying to run this program on ubuntu it compiles but when i run it it flags as ...

  1. #1
    Registered User
    Join Date
    Aug 2012
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    1

    Unhappy ERROR: segmentation fault (core dumped)

    when i am trying to run this program on ubuntu it compiles but when i run it it flags as "segmentation fault (core dumped)". can anyone tell me how to get the output.the code is as follows:

    Code:
    #include<stdio.h>
    #include<stdlib.h>
    
    
    struct node{
    int info;
    struct node*link;
    };
    void append(struct node**, int);
    void displ(struct node*);
    
    
    
    
    void append(struct node **q, int n){
     struct node *temp,*r;
    
    
    if(*q==NULL){
    printf("the list has zero elements and the first node being added is %d\n",n);
    temp->info=n;
    temp->link=NULL;
    *q=temp;
     }
    else
    {temp=*q;
      while(temp->link!=NULL)
          temp=temp->link;
    
    
    r=malloc(sizeof(struct node));
    r->info=n;
    r->link=NULL;
    temp->link=r;
    }
    
    
    }
    
    
    void displ(struct node *q){
    struct node *p;
    for(p=q;p->link!=NULL;p=p->link)
     printf("%d",p->info);
    
    
    }
    
    
     main(){
    struct node *p;
    int n;
    p=NULL;
    printf("enter value to append a node\n");
    scanf("%d",&n);
    //append(&p,12);
    displ(p);
    }

  2. #2
    C++ Witch laserlight's Avatar
    Join Date
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    Location
    Singapore
    Posts
    23,631
    For starters, you need to format your code better, especially the indentation:
    Code:
    #include<stdio.h>
    #include<stdlib.h>
    
    struct node {
        int info;
        struct node *link;
    };
    
    void append(struct node**, int);
    void displ(struct node*);
    
    void append(struct node **q, int n) {
        struct node *temp, *r;
    
        if (*q == NULL) {
            printf("the list has zero elements and the first node being added is %d\n", n);
            temp->info = n;
            temp->link = NULL;
            *q = temp;
        }
        else {
            temp = *q;
            while (temp->link != NULL)
                temp = temp->link;
            r = malloc(sizeof(struct node));
            r->info = n;
            r->link = NULL;
            temp->link = r;
        }
    }
    
    void displ(struct node *q) {
        struct node *p;
        for (p = q; p->link != NULL; p = p->link)
            printf("%d", p->info);
    }
    
    main() {
        struct node *p;
        int n;
        p = NULL;
        printf("enter value to append a node\n");
        scanf("%d", &n);
        //append(&p,12);
        displ(p);
    }
    Next, one problem you have is that when inserting the first node, you forgot to allocate memory for it.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  3. #3
    ZuK
    ZuK is offline
    Registered User
    Join Date
    Aug 2005
    Location
    Austria
    Posts
    1,990
    You're passing NULL for q

    Code:
    void displ(struct node *q){
        struct node *p;
        for(p=q;p->link!=NULL;p=p->link) // <<== boom
             printf("%d",p->info); // <<= boom
    }
    Running the program in the debugger helps a lot to find this kind of errors.
    Kurt
    rags_to_riches likes this.

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