output for array of pointers is not giving correct values

HI ,

I am giving 1 and 2 inputs for below program.

output giving some other values as i exptectd.

I am expecting 1 and 2 as outputs.

any one can help me ?

Code:

---

int main()
{
        int *p[2]={};
        int i;

        for (i=0;i<2;i++);
        {
                printf ("enter the nubmer \n");
                p[i]=malloc(sizeof (int ));
                scanf ("%d",p[i]);
                printf ("%d\n",*p[i]);
        }

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




output :

enter the nubmer
1
1
Segmentation fault

---

Did you include <stdlib.h> ?

Try this, instead:

Code:

---

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

int main()
{
        int *p[2];
        int i;

        for (i=0;i<2;i++)
        {
                printf ("enter the nubmer \n");
                p[i]=malloc(sizeof (int ));
                scanf ("%d",p[i]);
                //printf ("%d\n",*p[i]);
        }

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

Remove the semi-colon from the end of the first line of the for loop code, and fix the int *p line.

---

What include files are you including?

When I compile the code as provided I get these error messages:

Quote:

---

main.c||In function ‘main’:|
main.c|4|error: ISO C forbids empty initializer braces|
main.c|9|error: implicit declaration of function ‘printf’|
main.c|9|warning: incompatible implicit declaration of built-in function ‘printf’|
main.c|10|error: implicit declaration of function ‘malloc’|
main.c|10|warning: incompatible implicit declaration of built-in function ‘malloc’|
main.c|11|error: implicit declaration of function ‘scanf’|
main.c|11|warning: incompatible implicit declaration of built-in function ‘scanf’|
main.c|17|warning: incompatible implicit declaration of built-in function ‘printf’|
||=== Build finished: 4 errors, 4 warnings ===|

---

Jim

Quote:

---

Originally Posted by jimblumberg

What include files are you including?

When I compile the code as provided I get these error messages:



Jim

---

Hi Jim,

I am compiling on linux mechine.

I am not getting any compilation errors.

hope you can are compiling on windows. I think u need to add
#include<stdio.h>
#include<conio.h>
#include<malloc.h>

But i am not sure.

Code:

---

        for (i=0;i<2;i++);  <-- WHOOPS
        {
                printf ("enter the nubmer \n");
                p[i]=malloc(sizeof (int ));
                scanf ("%d",p[i]);
                printf ("%d\n",*p[i]);
        }

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

---

That semi-colon means the if() is not associated with the following block, so i == 2 when it executes. This allocates and assigns p[2], which could cause a seg fault right there, but evidently it by chance does not.

The seg fault you get happens when the second if() loop starts, because p[0] was never initialized, therefore contains some random address which is dereferenced for a value (but it is out of bounds).

For malloc() you should:

Code:

---

#include <stdlib.h>

---

HI Adak,

if i added also i am getting same output.( segmentfault).

Hi Mk27,

yes. It my mistake. Now i am getting correct values. Thanqu very much.

Quote:

---

Originally Posted by nkrao123@gmail.

I am compiling on linux mechine.
I am not getting any compilation errors.

---

You should compile with warnings enabled:

gcc -Wall

Which will give you a clue about having not included stdlib.h for malloc().

Quote:

---

I am compiling on linux mechine.

I am not getting any compilation errors.

hope you can are compiling on windows. I think u need to add
#include<stdio.h>
#include<conio.h>
#include<malloc.h>

But i am not sure.

---

I am compiling on a Linux machine as well.

You need to include stdio.h for printf(), scanf() and stdlib.h for malloc().

You need to compile with at least the -Wall compiler option to emit at least the standard warning messages.

Jim