Re: Wherer is the Segmentation fault?

[Aubin LaBrosse <zoticus at gmail dot com>]

In randomidxval - you never malloc entry. 

Sent from my iPhone

On Nov 30, 2010, at 10:23 PM, Vaibhav Kaushal <vaibhavkaushal123@gmail.com> wrote:

> I am trying to dump a list of simple structure of two fields (roll
> number and name of student) into a file but it is failing. here is the
> code:
> 
> ====================================
> 
> #include <stdio.h>
> 
> //structure of entry
> typedef struct {
>    int rollno;
>    char name[60];
> } entry;
> 
> entry *newentry;
> 
> entry* randomidxval(int x){
>    printf("\n Entering randomidxval");
>    entry *newentry;
>    newentry->rollno = x;
>    int i=0;
>    for (i=0; i<60; i++) {
>        newentry->name[i]=x;
>    }
>    printf("\n Exiting randomidxval");
>    return newentry;
>    
> }
> 
> void create () {
>    printf("\n Entering create");
>    
>    FILE *indx;
>    //entry *temp;
>    int i;
>    indx = fopen("indx.dat", "wb" );
>    if(indx) {
>        for (i=0; i<2; i++) {
>            printf("\n Entering loop");
>            printf("\n Before allocation");
>            //temp =  randomidxval(i);
>            printf("\n After allocation");
>            printf("\n Before condition");
>            if(0 != fwrite (randomidxval(i), sizeof(entry), 1 , indx)) {
>                printf("\n Write Successful %d", i);
>            } else {
>                printf("\n Write Failed");
>            }
>            printf("\n After Condition");
>        }
>    } else {
>        printf("\n File open failed");
>    }
>    //temp=malloc(1);
>    //free(temp);
> 
> /* Removing or altering the above two lines to free memory does not
> affect the error */
> 
>    printf("\n Close %s", fclose(indx) == 0 ? "succeeded" : "failed");
> 
> 
> /* It is in the following line that the problem exists. The fuction
> never executes the last line and shows a segmentation fault. No matter
> what I do, the function will fail before returning. I have tried a lot
> but no help */
> 
>    printf("\n Exiting create");
>    return;
> }
> 
> void search () {
>    printf("\n Entering search");
>    printf("\n Exiting search");
>    return;
>    
> }
> 
> int main() {
>    printf("\n Entering main");
>    
>    printf ("\n Actions: \n 1. Create index \n 2. Search \n Please choose
> your operation : ");
>    int choice = 1;
>    scanf ("%d", &choice);
>    if(choice==1) {
>        printf("\n Launching Create");
>        create();
>        printf("\n Create returned");
>    } else {
>        search();
>    }
>    printf (" \n ");
>    //printf("\n %d \n", *choice);
>    //free *choice;
>    printf("\n Exiting main");
>    return 0;
> }
> 
> ======================================
> 
> 
> The problem is that the function create never returns!!
> 
> can someone tell me the reason and how to resolve it? the program
> compiles well with no warnings or errors. 
> 
> My system is Fedora Linux 13 , 64-bit.
>