Segmentation fault after main returns (pointer to struct array)

Question

#include <stdio.h>
#include <stdlib.h>
#define VEL 2
typedef struct
{
    char ime[15];
    char prezime[15];
    int dob;
    int staz;
} employee;
void upis(employee *);
void ispis(employee *);
int main(int argc, char **argv)
{
    employee radnik[VEL];

    upis(&radnik[VEL]);
    ispis(&radnik[VEL]);
    return 0;
}

void upis(employee * r)
{
    int i;

    printf("Upis podataka:\n==============\n");
    for (i = 0; i < VEL; i++)
    {
        printf("Upisite ime i prezime %d. radnika:\n", i + 1);
        scanf(" %15[^\n]", (r + i * sizeof(employee))->ime);
        scanf(" %15[^\n]", (r + i * sizeof(employee))->prezime);
        printf("Upisite dob i staz %d. radnika:\n", i + 1);
        scanf("%d", &(r + i * sizeof(employee))->dob);
        scanf("%d", &(r + i * sizeof(employee))->staz);
    }
}

void ispis(employee * r)
{
    int i;

    for (i = 0; i < VEL; i++)
    {
        printf("Ime:%s\nPrezime:%s\n", (r + i * sizeof(employee))->ime,
               (r + i * sizeof(employee))->prezime);
        printf("Dob:%d\nStaz:%d\n\n", (r + i * sizeof(employee))->dob,
               (r + i * sizeof(employee))->staz);
    }
}

The code actually works but in the end always returns segmentation fault. I'm guessing I did something wrong with pointers and addressing struct elements. Please help and thanks in advance!!

EDIT: Thanks everyone each answer was helpful!

Community · Accepted Answer · 2017-05-23 11:57:32Z

4

Error is expressions like:

(r + i*sizeof(employee))->ime;

Correct it as:

(r + i)->ime;

Read Pointer to structure To learn how to use pointer to struct.

Note pointer arithmetic is different then integer arithmetic. When you add 1 to a pointer resulting address point to next location (you do not need to bother to calculate value). Accordingly in your code if r point to n^th employee in an array of employee then r + 1 points to (n + 1)^th employee.
To understand read 10.2 Pointers and Arrays; Pointer Arithmetic and Pointer Arithmetic.

Edit:

As @Jens Gustedt Notice correct your main code also as follows:

upis(radnik);
ispis(radnik);

If you wants to pass array to function (or first element's address).

Additionally avoid scanf to read line instead use fgets() read Reading a line using scanf() not good?.

edited May 23, 2017 at 11:57

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answered Oct 8, 2013 at 11:22

Grijesh Chauhan

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1 Comment

lurker Over a year ago

Along with this, it would be good to explain for the OP that, in C, when you add an integer to a pointer, the pointer is incremented by an amount equal to that integer times size of the type pointed to by the pointer.

Jens Gustedt · Accepted Answer · 2013-10-08 11:45:47Z

2

This code is fundamentally flawed:

employee radnik[VEL];

upis(&radnik[VEL]);
ispis(&radnik[VEL]);

Arrays in C are indexed from 0 on to VEL-1 in your case. You are taking the address of of an element beyond the array and use it afterwards. This has no defined behavior, so anything can happen.

answered Oct 8, 2013 at 11:45

Jens Gustedt

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1 Comment

Grijesh Chauhan Over a year ago

Actually this is first bug..I couldn't notice.

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