Declaring automatic variables inside a while loop

Declaring automatic variables inside a while loop

[Swaminathan Venkatakrishnaprasad]

Hello,

Could you please let me know if it is 
valid to declare an automatic variable 
inside a for loop. If yes, is it also allowed
in ANSI standard (could you please refer
me to the sec #).

Example:
void f()
{
    int i;
    i = 10;
    while(i >=0 )
    {
       int j;
       i=j;
       printf("j=%d \n", j);
       i--;
    }
return;
}

Also, in the above example would
the number of iterations contribute anything to the stack
size since an automatic variable is declared
inside the while loop??

Your input is very much appreciated.

Thanks & Regards,
Swaminathan Venkat

Re: Declaring automatic variables inside a while loop

[Jim Wilson]

Swaminathan Venkatakrishnaprasad wrote:
> Could you please let me know if it is 
> valid to declare an automatic variable 
> inside a for loop.

This has always been legal.  The loop body is just a compound statement, 
  same as a function body.

> If yes, is it also allowed
> in ANSI standard (could you please refer
> me to the sec #).

3.6.2, Compound Statement or Block, in the 1989 ANSI C standard.

> Also, in the above example would
> the number of iterations contribute anything to the stack
> size since an automatic variable is declared
> inside the while loop??

No.  The variable is allocated only once.

By the way, in your example, you are setting the loop iterator (i) to an 
uninitialized local (j) which isn't going to work.
-- 
Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com

Re: Declaring automatic variables inside a while loop

[Andrea 'Fyre Wyzard' Bocci]

>By the way, in your example, you are setting the loop iterator (i) to an 
>uninitialized local (j) which isn't going to work.

Well, it's going to "work", if you don't care what the actual behaviour is 
- ie., if the code hangs at random executions...

.fw. 

Re: Declaring automatic variables inside a while loop

[Robert Dewar]

Andrea 'Fyre Wyzard' Bocci wrote:

> 
>> By the way, in your example, you are setting the loop iterator (i) to 
>> an uninitialized local (j) which isn't going to work.
>  
> Well, it's going to "work", if you don't care what the actual behaviour 
> is - ie., if the code hangs at random executions...
        ^^

I assume you meant eg here (i.e. this is an example), since this is only
one of many horrible things that could happen :-)