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return value from main

Discussion in 'C' started by abhishek.biradar, Sep 1, 2010.

  1. abhishek.biradar

    abhishek.biradar New Member

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    check the following program
    /*a.c*/
    int main()
    {
    return 0;
    }
    returns 0 to the shell and echo $? gives 0
    /*b.c*/
    void main()
    {
    }
    echo $? in shell gives some different values for each execution what does it represents????
     
  2. shabbir

    shabbir Administrator Staff Member

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    Garbage values
     
  3. xpi0t0s

    xpi0t0s Mentor

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    It represents the fact that you haven't returned a value. The values are meaningless; you should not try to use them if the program doesn't return a value. But you should always return zero from main unless you have a good reason for returning some other specific value; zero indicates success, and for any script calling your program and relying on the return codes to check for errors a garbage return will cause undefined behaviour within the script.

    If you know for certain that your program will NEVER EVER be called by a script that checks return values, and that returning garbage will definitely have no negative effects, then go ahead and return garbage. Otherwise at least return 0; it's not a difficult line to add. Or return EXIT_SUCCESS; if you prefer.
     
  4. DaWei

    DaWei New Member

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    Always define main as returning an int, then return one. It's that simple.
     
  5. shabbir

    shabbir Administrator Staff Member

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    [comment]After long time and so welcome back.[/comment]
     
  6. LordN3mrod

    LordN3mrod New Member

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    The current C++ standard mandates that the main() function return int. However you don't have to ACTUALLY return a value. If the control flows out of main without reaching a return statement, it is equivalent to return 0;
    On the other hand,
    void main() is ill-formed
     
    shabbir likes this.

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