Parameter and return value specifics

This is a discussion on Parameter and return value specifics within the C Programming forums, part of the General Programming Boards category; Hello everyone, Studying C in school and have just a couple questions that I have seemingly answered with the compiler ...

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    Parameter and return value specifics

    Hello everyone,
    Studying C in school and have just a couple questions that I have seemingly answered with the compiler but have not been able to find in any books..

    1.) Is there any difference between a funtion with no parameters that does not include anything between the parenthesis and one that only includes the data type void? In other words, any difference between "int main ()" and "int main (void)"? I've experimented with both and observed no difference.

    2.) Is there any difference between an integer main function that returns 0 and a void main function? I noticed that most reputable C books teach the reader to declare main as an integer returning function but many tutorials also just use void ("void main (void) and void main()"). Likewise, I've experimented with this in the compiler as well and observed no difference.

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    Just kidding.... fnoyan's Avatar
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    A links from C-FAQ

    http://c-faq.com/decl/main.html

    Also, I recommend you to have a look at http://c-faq.com/

    foo(void) means this function accepts no parameters. void is used to declare that the function has no parameters.

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    1 == 1 tzpb8's Avatar
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    I know one.. but dont know if it is relevant though..
    The "Dev-C++ (v4.9.9.2) " compiler (dont know about earlier versions), gives an error if you try to define main() as a void function though in memory i think i remeber defining main() as a void function some time ago..

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    pronounced 'fib' FillYourBrain's Avatar
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    Quote Originally Posted by Zaff
    1.) Is there any difference between a funtion with no parameters that does not include anything between the parenthesis and one that only includes the data type void? In other words, any difference between "int main ()" and "int main (void)"? I've experimented with both and observed no difference.
    not in today's versions... but I think... now don't quote me on this cause I wasn't around for this, but I think some of the original versions had a different meaning for the empty parameter list.
    Quote Originally Posted by Zaff
    2.) Is there any difference between an integer main function that returns 0 and a void main function? I noticed that most reputable C books teach the reader to declare main as an integer returning function but many tutorials also just use void ("void main (void) and void main()"). Likewise, I've experimented with this in the compiler as well and observed no difference.
    the difference is that void main is non-standard.
    "You are stupid! You are stupid! Oh, and don't forget, you are STUPID!" - Dexter

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    Code Goddess Prelude's Avatar
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    >In other words, any difference between "int main ()" and "int main (void)"?
    It depends on where you use it. For a function declaration, there's a subtle and disturbing difference:
    Code:
    void foo(); // Takes an unknown number and type of parameters
    void foo ( void ); // Takes no parameters
    For a function definition, there's still a minor difference:
    Code:
    // Does not ensure a complete prototype
    void foo()
    {
    }
    
    // Ensures a complete prototype
    void foo ( void )
    {
    }
    A full prototype, of course, guarantees that you'll be informed of improper use of the function. You should always use void when you intend for a function to have no arguments, and you should refrain from using empty parameter lists because it's a feature of the language that's being phased out with new revisions of the standard. It's also dangerous.

    >Is there any difference between an integer main function that returns 0 and a void main function?
    Yes, main returning an integer is correct and main returning anything else is not. The C standard makes it very clear that the following declarations of main (and anything directly equivalent) are allowed:
    Code:
    int main ( void );
    int main ( int argc, char *argv[] );
    Anything else is implementation-specific. It could either work if your implementation allows it, or invoke undefined behavior. That kind of uncertainty makes using void main exceptionally stupid.
    My best code is written with the delete key.

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    Thumbs up

    Thanks alot guys, great answers in no time at all. Definetly one of the better C forums online.

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