Thread: Huh. int main() acts like char main(). Whoda thunk.

  1. #1
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    Huh. int main() acts like char main(). Whoda thunk.

    Hello:


    (Ubuntu 18.04 gcc version 7.5.0)


    Ok... here I thought; "int main()" returned an int. So I tried "return(256)" and bash ($?) reports '0'. "return(255)" reports '255'. Why does main() seem to be limiting to what looks like a CHAR?


    And, equally curious, if I try "char main()", the program compiles w/ warning. Using "return('G')" to bash ($?) reports '71', which is decimal for Capital-G.


    Recompiling back to int main(), and trying "return(512)" reports '0', and "return(513)" reports '1'. Looks like return(whatever_value % 256) is the behavior.


    For my x86_64, using #include <limits.h> reports:


    The minimum value of SHORT INT = -32768
    The maximum value of SHORT INT = 32767
    The minimum value of INT = -2147483648
    The maximum value of INT = 2147483647


    'Ya learn something every day.......
    Thx

  2. #2
    and the hat of int overfl Salem's Avatar
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    wait(2): wait for process to change state - Linux man page

    Scroll down to WEXITSTATUS

    Read what it says.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

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    Registered User rstanley's Avatar
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    main() does return an int, but Linux limits the value to the range, 0 - 255, as specified by GNU here.

    Other O/S's might allow a different range.

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    Quote Originally Posted by Salem View Post
    wait(2): wait for process to change state - Linux man page

    Scroll down to WEXITSTATUS

    Read what it says.
    Sorry, I have no idea what this means, or how it applies here. Thx.

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    Quote Originally Posted by rstanley View Post
    main() does return an int, but Linux limits the value to the range, 0 - 255, as specified by GNU here.

    Other O/S's might allow a different range.
    Well, that's clear enough. I am working on a 'C' tutorial series, and this cropped up unexpectedly. Thx.

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