main return value stange question

[Sweety]

hello to all members,

i have strange question in C.
main()
{
printf("%d",mai n) ;
}

here o/p is same for all m/c in TC++ version 3.0 i.e 657.
I think this is not garbage.
what u think??
plz reply.

[Peter Shaggy Haywood]

Groovy hepcat Christopher Benson-Manica was jivin' on Tue, 23 Dec 2003
22:02:38 +0000 (UTC) in comp.lang.c.
Re: main return value stange question's a cool scene! Dig it!

Mike Wahler <mk******@mkwah ler.net> spoke thus:

main()
{
printf("%d",mai n) ;
}

The behavior of the above program is undefined.

Of course - the challenge is to enumerate all the different ways it
can explode :) I'll give it a shot...

1) main() will work fine on a C89 implementation, but will be rejected
by a mythical C99 implementation. Yes?

If you mean the declaration of main() without specifying the return
value (relying on implicit int), then yes.
2) There is no newline in the printf.
3) Implicitly casting main's function pointer (is that what it is in that
context?) to an int.
Nope. That's not happening here. The function designator, main, is
converted to a pointer to function, and this is passed to printf().
This is then treated as if it were an int (but is never cast, either
implicitly or explicitly, to anithing). I think that's what you meant.
The behaviour is undefined.
4) Nothing is returned, which is fine for C99 but not C89... right?
Not exactly. Something is returned, but in C90 it is an
indeterminate value.
5) stdio.h wasn't included (in the post itself, at least)
Right; so there is no prototype for printf(). Calling a var args
function without a prototype causes undefined behaviour.
Does the behavior improve if the program is changed to

#include <stdio.h>

int main()
{
printf( "%p\n", (void *)main );
return EXIT_SUCCESS;
}

Yes. Now we know it won't compile, since EXIT_SUCCESS is an
undeclared identifier. (Well, strictly speaking, in theory, we don't
know anithing except that a diagnostic will be produced. What happens
next is undefined. But in the real world, a compiler will cease
compilation.)

--

Dig the even newer still, yet more improved, sig!

http://alphalink.com.au/~phaywood/
"Ain't I'm a dog?" - Ronny Self, Ain't I'm a Dog, written by G. Sherry & W. Walker.
I know it's not "technicall y correct" English; but since when was rock & roll "technicall y correct"?

[Christopher Benson-Manica]

Peter "Shaggy" Haywood <sh****@austral is.net.stop.spa m> spoke thus:

Yes. Now we know it won't compile, since EXIT_SUCCESS is an
undeclared identifier.

Hey, I accomplished something ;) I seem to have a terminal problem
with neglecting to include <stdlib.h> when using EXIT_SUCCESS.

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cybers pace.org | don't, I need to know. Flames welcome.