Arrays with Pointers

[cena06]

hi =)
i have tried to save array values with pointers but i got "segmentation fault".
how can i do it corectly?

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

void main()
{
    
    int *pdizi[3]={NULL};
    int i;

    for(i=0; i<3; i++)
    scanf("%d",pdizi[i]);

    for(i=0; i<3; i++)
    printf("%d\t%p\n",*pdizi[i],pdizi[i]);

}

[kmdv]

for(i=0; i<3; i++)
scanf("%d",pdizi[i]);

This code loads garbage, and pointers are assigned some unspecified values.
Later you try to dereference this garbage (dereferece invalid pointers), hence the error.

Probably a simple non-pointer array would suffice

[cena06]

int dizi[3];
    int *pdizi[3]={NULL,NULL,NULL};
    int i;

    for(i=0; i<3; i++)
    dizi[i]=i*i;

    for(i=0; i<3; i++)
    pdizi[i]=&dizi[i];

    for(i=0; i<3; i++)
    printf("%d\t%p\n",*pdizi[i],pdizi[i]);

    for(i=0; i<3; i++)
    scanf("%d",pdizi[i]);


    for(i=0; i<3; i++)
    printf("%d\t%p\n",*pdizi[i],pdizi[i]);

when i do it, i dont get any error
it works
nevertheless i want to know why it doesnt work when i get array values with pointers directly?

[Click_here]

hi =)
i have tried to save array values with pointers but i got "segmentation fault".
how can i do it corectly?

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

void main()
{
    
    int *pdizi[3]={NULL};
    int i;

    for(i=0; i<3; i++)
    scanf("%d",pdizi[i]);

    for(i=0; i<3; i++)
    printf("%d\t%p\n",*pdizi[i],pdizi[i]);

}

pdizi is declared as an array of pointers - You initialise all the pointers to NULL

You then try to put a value at the location of pdizi, which is pointing to NULL (You are not allowed to do this), so you get a seg fault.

Changing pdizi to a non-pointer array will fix the issue. (Don't forget to use the '&' address of operator in the scanf)

[grumpy]

nevertheless i want to know why it doesnt work when i get array values with pointers directly?

I suspect you're making the classic beginner mistake of believing that a pointer and an array are the same things. They are not.

The reason your second code sample works is because you have made the pointers in pdizi equal to the addresses of elements of dizi. Such pointers can be dereferenced as long as the array dizi exists.

The first code sample does not work, because the elements of pdizi are NULL pointers. Dereferencing a NULL pointer gives undefined behaviour (of which a common symptom is a program crash, such as a segmentation fault).