how to solve this bug??

when i run this code
instead of getting some expected out put i get

line 17: `main' must return `int'

but main is a void function

it cant return int
???

Code:

---


#include <stdio.h>
int a(int n,int count){
      int i;
      for(i=0;i<n;i++)
          count =a(i,count);
          return count+1;
}

int b(int n,int count) {
  int i;
  count =a(n,count);
    for(i=0;i<n;i++)
    count =b(i,count);
    return count;
  }

  void main (){
    int i;
    for (i=0;i<4;i++)
      printf("%d",a(i,0));
      printf("\n%d\n",a(i,10));

      for (i=0;i<4;i++)
        printf("%d",b(i,0));
        printf("\n%d\n",b(i,10));

  }

---

Actually it is telling you that try as you may, you aren't supposed to ever have it be void.

Just change it to int. The return value is optional.

but its a void function

i dont want it to return integer

why its a bug
why main cannot be void??

The people (ANSI/ISO committee) who are in charge of C say so. And for that matter, you may not want it to return an integer, but Windows/Linux/OS X/various other operating systems certainly do.

It isn't a bug per se, so much as its just breaking of the standard. In other words, how can it be a bug if it won't compile without complaint? I would reserve the word bug for those pesky things that your compiler doesn't mention to you.

i copied this code from a test question which asks to find the output of this code

and the answer is some numbers

there is no way that this code has a bug
i cant see what did i missed

this is the original stuff
did i missed some thing

http://img216.imageshack.us/my.php?i...5165572gm4.gif

??

Think that when the main program finishes it will return an int. That information might be helpful or even vital for the OS to know if the program succeeded or not. The default is return 0

Quote:

---

Originally Posted by transgalactic2

i copied this code from a test question which asks to find the output of this code

and the answer is some numbers

there is no way that this code has a bug
i cant see what did i missed

this is the original stuff
did i missed some thing

http://img216.imageshack.us/my.php?i...5165572gm4.gif

??

---

Generally, in C both types can be used. Either void main or int main. Just int main is preferred so why not use it? You are getting a warning or an error?

The first thing you need to realise is the world is knee deep in idiots who think void main (and lots of other horrors) are perfectly valid C.

Unfortunately, many of these people tend to write books or teach at 2nd rate universities, rather than be professional programmers.

Ok lets break this into a more general thing.

You: Matt how do you enter a C program?
Me: Well Billy, you simply create a main() function.
You: main() function?
Me: According to the C standard, a main() function can take one of two forms.
You: Can you post them in code tags since you can't possibly demonstrate this concept verbally?
Me: Haha Billy, of course I can.

(Matt pats Billy on the head)

Example:

Code:

---

/*
 *  First form: With no parameters.
 */
int main(void)
{
  return 0;
}

/*
 * Second form: With parameters.
 */
int main(int argc, char **argv)
{
  return 0;
}

---

Anything else would be wrong.

Untitled2.c|17|error: `main' must return `int'|
||=== Build finished: 1 errors, 0 warnings ===|

So change it to int, already.

(It won't affect your instructor's answer.)

Again, be proud that your compiler absolutely refuses to accept your function. Many will demote this practice down to a mere warning.

Again I say just change the void to an int and your code will compile with no other changes to your code.

Is there some problem with the dictionary definition of "must" which is troubling you?

Just change the void to int, and put a return 0; at the end and get on with life!

this is what he wrote

this is the code i must inspect

i get the idea that he made a mistake
thanks

I do some part time teaching. I assure you I am not perfect. Nor are you. So given these details it not already reasonable enough to assume that your teacher is capable of making mistakes?

lol! I just had a hilarious idea that is kind of inspired by King Mir.

Dysfunctionally correct...

Code:

---

#include <stdio.h>
#define void int
int a(int n,int count){
      int i;
      for(i=0;i<n;i++)
          count =a(i,count);
          return count+1;
}

int b(int n,int count) {
  int i;
  count =a(n,count);
    for(i=0;i<n;i++)
    count =b(i,count);
    return count;
  }

  void main (){
    int i;
    for (i=0;i<4;i++)
      printf("&#37;d",a(i,0));
      printf("\n%d\n",a(i,10));

      for (i=0;i<4;i++)
        printf("%d",b(i,0));
        printf("\n%d\n",b(i,10));

  }

---

Now everyone gets to be right :)

Let's not give transgalactic2 a hard time.

It is possible the original code was not a "bug" - if it compiled perfectly under a different, less picky compiler which isn't completely current-C-standard compliant.

Hence, it's only a bug if your C implementation says it's a bug. That's the one you have to respect.

It may not be fair, ethical, or legal, but whaddayagonnado?

I just wanted him to be fully aware that its not an issue of being a bug. Its an issue of being illegal. Besides, problem solved with my last post. Even an angry anti-social compiler can do what you need using that code. I just wouldn't make a habit of getting rid of void all the time...

I remember what it was like when the prof would give a problem and it had an obvious contradiction or bug in it. Sometimes even they get things out of some curriculum book and can't be entirely blamed. But to contradict the prof in order to get the assignment done, well, I got my fill of being labelled a "difficult student". LOL.

For me, I would rather write diabilically genius code to circumvent short-comings of the original code.

i use code blocks 8.02 compiler

do you think i need to get another compiler?

Quote:

---

Originally Posted by master5001

I just wanted him to be fully aware that its not an issue of being a bug. Its an issue of being illegal.

---

Actually, I am convinced that even in C99, void is permitted as a return type for the main function on a hosted environment, though this is a defect in the C standard. See void main() is not legal in C++ but is legal in C.

Quote:

---

Originally Posted by transgalactic2

i use code blocks 8.02 compiler

do you think i need to get another compiler?

---

Code Blocks is not a compiler, but an IDE. You can change your code to use int main() and return 0 when developing your code, and then just switch to void main() when you want to submit your code.

> Hence, it's only a bug if your C implementation says it's a bug. That's the one you have to respect.
This is a complete load of tosh!

char *buff;
gets( buff );
Now if this just happens to work on crapware 1.0, does that make it a bug-free program?

If it does work, and you know no better, would you continue to use the same style in the belief that it was in fact the correct thing to do, just because the compiler didn't complain, and the code seemed to work?

Or do you rely on knowledge of how C is defined to decide that it is in fact a horrible bug, without having to rely on a compiler to tell you that much.

The big problem with the "works for me" attitude is that when, years later, you change compiler from crapware 1.0 to smartware 10.0, and it starts complaining about all sorts of things. Even when it doesn't complain, the resulting code just crashes.

Who ya gonna blame?
- the new compiler for telling you the truth
- the old compiler for being a PoS
- your old teacher for selling you snake oil
- yourself for not listening to more experienced people when you had the chance to.

If you just rely on a single compiler to tell you whether there is a bug, then you're doomed to relearn C every time you change compilers.

@OP
You could always print off N869 and add it as an appendix to your homework submission, and cite it as a reference for your answers :)

Quote:

---

Originally Posted by Salem

@OP
You could always print off N869 and add it as an appendix to your homework submission, and cite it as a reference for your answers

---

However, as Jonathan Pollard pointed out in the article I linked to, even in the final version of the C99 standard the defect that allows an implementation to provide void main() on a hosted environment remains, so printing N869 is of no use if the instructor points out that his or her compiler permits it. At best, one can argue that this is not portable, since implementations are not required to permit it.

Quote:

---

Originally Posted by Salem

> Hence, it's only a bug if your C implementation says it's a bug. That's the one you have to respect.
This is a complete load of tosh!

---

That's not what I was saying. You are talking the difference between a syntactical error and semantical (if the English analogy applies), i.e. what happens during run-time.

If a student uses whatever compiler for his homework assignment, and it complains about some SYNTAX error, he needs to do whatever to fix the issues. That what he has to respect at-that-time. To get the thing compiling. Wouldn't you agree? The professor's code wouldn't even compile as-is. Under the local compiler. My comment makes no greater implications.

When the program compiles fine but still has latent memory access issues (uninitialized variables, pointers, accessing past arrays, etc.) these things may or may not be catchable with modern compilers which do a lot more logic flow analyses.

I never said that if a particular compiler passes your code alright, that it's bug free.

A implies B does not mean B implies A.

So is void main syntax or semantic, if your rubbish compiler accepts it?

If the OP wants to carry on learning crap from a prof who doesn't know C, then that's their problem. But at least it might now be an informed decision, rather than blindly assuming that everything the prof says is golden.

i talked to my teacher and he is 100% percent sure that this code works

and he doesnt know what i am talking about

i dont know why he thinks its ok
because abviosly main has to be int with return 0; in the end

i want to understand on want basis he writes that main function in that way

there is no way he made a typing mistake

here is the original code scanned from his exam:

http://img216.imageshack.us/my.php?i...5165572gm4.gif

after reading this document:
http://homepages.tesco.net/J.deBoyne...void-main.html

i understood that void main() is perfectly ok in C

and that my bug happened because i use C++ compiler

C++ allows anly int main()

The only compiler I know that "allows" void main is the Mingw compiler that comes with DevC++ ( old anyway ).

It allows it only if you compile the code with a .c extension and not a .cpp. But even then gives a warning suggesting it should be int main().

transgalactic2 I would seriously consider listening to everyone on this issue. Your proffessor is NOT correct in saying its ok to use void main(). This is 2008, you go out into the industry and use it in a commrical company on test console code you will get shot.

Its better to learn right then learn backwards.

Quote:

---

Originally Posted by transgalactic2

i understood that void main() is perfectly ok in C

---

Read carefully: void main() is legal if your compiler documents it as an option, and only because of a defect in the standard. Consequently, it is non-portable, because it is not required, though also not forbidden.

However, the difference between int main() and void main() is so minimal that there is really no reason to use void main() even when it is allowed, unless you are required to do so by some person in charge of your marks or your pay who you cannot convince otherwise. In that case, be pragmatic: use void main(), but know that you should not do so otherwise.

thanks