void main question..

This is a discussion on void main question.. within the C Programming forums, part of the General Programming Boards category; i know that we discussed it before and i learned that we write main like this: Code: int main() { ...

  1. #1
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    void main question..

    i know that we discussed it before and i learned that we write main like this:
    Code:
    int main()
    {
    
    return 0;
    }
    but when i started my course i was told "the way to write main is":

    Code:
    void main()
    {
    
    }
    i was skeptic regarding what they says until i wrote it in visual studio 2005
    and it even didnt put out a warning

    whyyyy??

  2. #2
    Code Goddess Prelude's Avatar
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    >whyyyy??
    Visual C++ is one of the compilers that supports void main as an extension. It's safe on that compiler, but by using it you've removed any possibility of your code being portable.

    And for future reference, "it compiles for me" and "it runs for me" are not synonymous with "it's correct".
    My best code is written with the delete key.

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    C++ Witch laserlight's Avatar
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    Quote Originally Posted by transgalactic2
    i was skeptic regarding what they says until i wrote it in visual studio 2005
    and it even didnt put out a warning
    Maybe the warning level was too low.

    EDIT:
    Oh yes, more like: maybe you did not disable language extensions.
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  4. #4
    C++まいる!Cをこわせ! Elysia's Avatar
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    Warning 2 warning C4326: return type of 'main' should be 'int' instead of 'void'
    But it really does require language extensions to be OFF, when they are ON (?) by default.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    Registered User slingerland3g's Avatar
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    Good programming practice would have main() return an int, at least. Main should return status upon exit. A good read on this would be

    http://www.eskimo.com/~scs/readings/...in.960823.html

  6. #6
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    I think part of the problem is that in Java, main() returns void, and people that switch back & forth between the languages a lot forget that main() returns an int in C/C++.
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    What's to remember? main() returns int, simple as that.
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    Quote Originally Posted by hauzer View Post
    What's to remember? main() returns int, simple as that.
    Yeah, but then if you try that in Java you get an error.
    I have the opposite problem. I try to write int main() in Java all the time.
    "I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008

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  9. #9
    and the hat of wrongness Salem's Avatar
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    Not to mention the prevalence of poor compilers which implemented void main, back from the days of DOS (which was so lame at recognising an exit status, that no body bothered), and the piles of cheap pulp-fiction books which had titles such as "teach yourself code mangler C++ in 42 minutes".
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    The OS returns an int from main, therefore using void main discards that value. Also on the off-chance that another program is monitoring it, using void main could cause problems. Anyway, compilers should at least support int main, if it doesn't, get anew one.
    The problem is clearly demonstrated in Salem's avatar.
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  11. #11
    C++まいる!Cをこわせ! Elysia's Avatar
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    Quote Originally Posted by P4R4N01D View Post
    The OS returns an int from main,
    Actually...
    The program returns something from main, to the runtime, to the OS.

    therefore using void main discards that value.
    Same here. The result is actually undefined. Your program can return whatever.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  12. #12
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    Well I think they should either make void main() illegal (a compile error) or define what it should do, such as alway returning 0.
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    Quote Originally Posted by cpjust View Post
    Well I think they should either make void main() illegal (a compile error) or define what it should do, such as alway returning 0.
    void main() *is* illegal, unless you have non-standard language extensions...

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  14. #14
    Registered User C_ntua's Avatar
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    Well, int main returns 0 if you don't return something. So there is no sense for void main to do the same. It should be a compile error with the option to be enabled, since there might be some use of it, like in an embedded system where the value of main won't be checked.

  15. #15
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    Quote Originally Posted by C_ntua View Post
    Well, int main returns 0 if you don't return something. So there is no sense for void main to do the same. It should be a compile error with the option to be enabled, since there might be some use of it, like in an embedded system where the value of main won't be checked.
    But on platforms where the return value of main() isn't used, why doesn't the compiler just allow you to use int main() but throw away the return value?
    "I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008

    "the internet is a scary place to be thats why i dont use it much." - billet, 03/17/2010

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