Globla and local variables

**ssharish2005** · 11-18-2006

Hi,
I don't understand this. Why the result is always 0. have a look at this code

Code:

#include<stdio.h>

int count;

void test(int count)
{
    if(count==10)
        return;
    else
    {
        printf("%d\n",count);
        test(count++);
    }
}

int main()
{
    test(0);
    
    getchar();
    return 0;
}

As u can see in the function test. It has been called recu incrementing count by 1 every time it call back. why it dost show the value 0 - 9 rather than to be infinite loop with just 0.

But when it refers int global value count we get the right answer. Thats right, but the local variable count is not why??

ssharish2005

**noodles** · 11-18-2006

It's printing 0 infinitely because you're not passing the incremented value to test in the recursive call.

To make it work use

Code:

test(++count); /*pre-increment*/

instead of

Code:

test(count++); /*post-increment*/

EDIT: Note that a new copy of the variable is created at each function call.

**quzah** · 11-19-2006

To clarify, "count" the global variable does nothing in this code. As a matter of fact, your compiler should warn you about that, if you were actually to enable warnings. You have a local variable by the same name. The local scope overrides the global scope, using that varaible, not the global one.

Quzah.

**Salem** · 11-19-2006

And there's a compiler flag to tell you what Quzah just told you.

Code:

$ gcc -Wshadow foo.c
foo.c:5: warning: declaration of 'count' shadows a global declaration
foo.c:3: warning: shadowed declaration is here

**ssharish2005** · 11-19-2006

Heyy thats was my bad, i dint turn on my warning. Thanks very much guys.

ssharish2005

**Salem** · 11-19-2006

1. Don't use global variables.
2. If you must use global variables, then give them a distinctive namespace.

Like your global would have been called
int g_count;

**ssharish2005** · 11-19-2006

Just have one more question. Well i know i shouldn't do this, just to know how to do, thats it

how do i explictly specific to say that i am refering the global even through global and local varibales names are same. I know there is scope resolution operator. How do we use it in C

ssharish2005

**Salem** · 11-19-2006

You (*)can't do it in C, since it has no scope resolution operator.

(*)
Well I suppose you might be able to fake something with some pre-processor horror, but it sure wouldn't be pretty.

**ssharish2005** · 11-19-2006

Originally Posted by Salem

You (*)can't do it in C, since it has no scope resolution operator.

(*)
Well I suppose you might be able to fake something with some pre-processor horror, but it sure wouldn't be pretty.

Thanks very much salem.

ssharish2005

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