pointer array doesn't gets printed

Question

#include <stdio.h>
#include <stdlib.h>
void main()
{
    int i;
    int *as[2];
    for(i=0;i<2;i++)
    {
        *as[i]=i;
        printf("%d\n",*as[i]);
    }
}

This is my code. I am expecting to print values 1 2

But when I run the code the console prints nothing. What have I done wrong?

You should probably have gotten a warning about this from the compiler... except that you don't. So, I've filed [this one](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102996) against GCC and [this one](https://bugs.llvm.org/show_bug.cgi?id=52343) against clang. Which compiler were you using? — einpoklum, Oct 29 '21 at 07:36

score 0 · Accepted Answer · answered Oct 29 '21 at 07:16

0

The * character in C language is not a simple decoration. It declares a pointer that has to point to something. Here you declared an array of two pointers, but never initialized the pointer themselves. And dereferencing an uninitialized pointer is explicitely Undefined Behaviour (the hell for C programmers). If you want to process integers, get rid of the pointers:

int as[2];
for(i=0;i<2;i++)
{
    as[i]=i;
    printf("%d\n",as[i]);
}

Or if you really want to process pointers, ensure that they are initialized to point to a valid object:

int *as[2];
int data[2]
for(i=0;i<2;i++)
{
    as[i] = &(data[i]);   // Ok, as[i] now points to a valid integer
    *as[i]=i;
    printf("%d\n",*as[i]);
}

BTW, the idiomatic way to get the address of an element of an array would be:

    as[i] = data + i;

answered Oct 29 '21 at 07:16

Serge Ballesta

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i want to use pointer in my program, but could you help me to initialize a pointer array using allocation rather than using & of another variable – Kishore Kumar S Oct 29 '21 at 07:28
@KishoreKumarS Look for the `malloc` function in your C programming book. – Lundin Oct 29 '21 at 07:29
Apparently, though OP is not getting a warning about this from GCC. – einpoklum Oct 29 '21 at 07:37
int *as; as=malloc(2*sizeof(int)); IT WORKS – Kishore Kumar S Oct 29 '21 at 07:37

pointer array doesn't gets printed

1 Answers1