what is macro

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  1. #1
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    what is macro

    What are macro in c and how they are defined

  2. #2
    Devil's Advocate SlyMaelstrom's Avatar
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    Macros are a preprocessor directive that replaces the macro name with the code in the definition before compilation.
    Code:
    #include <stdio>
    
    #define myMacro printf("Hello World")
    
    int main() {
       myMacro;
    
       return 0;
    }
    There's about a dozen and a half reasons not to use macros, but that's how they are defined if you wished to use them. Consider using inline functions instead.
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    Quote Originally Posted by SlyMaelstrom
    Consider using inline functions instead.
    Hellow !!! this is a c forum not c++.

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    Supermassive black hole cboard_member's Avatar
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    You can inline functions in C, genius.




    (Right?)
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    Devil's Advocate SlyMaelstrom's Avatar
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    Yes, that's correct, my bad. Either way, avoid macros.

    Quote Originally Posted by ahluka
    You can inline functions in C, genius.
    (Right?)
    No, I don't believe it's standard. Some compilers will take it, but I think it just ignores the keyword when you compile a C source.

    EDIT: Off of a little research it seems inlining was fully accepted into the C99 standard, so it may actually be applied in C code. I'm not positive, though.
    Last edited by SlyMaelstrom; 05-02-2006 at 08:05 AM.
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    Supermassive black hole cboard_member's Avatar
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    Ok I didn't know that.

    EDIT: You must be able to. I swear I've done it before. Unless I tricked myself into thinking I was using C. Hmm.

    EDIT2: You have to stop editing at the same time as me.
    Good class architecture is not like a Swiss Army Knife; it should be more like a well balanced throwing knife.

    - Mike McShaffry

  7. #7
    erstwhile
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    c99 does support function inlining. Unfortunately, many people use microsoft compilers which do not handle c99.

    Gcc does, though - just compile with -std=c99.
    Last edited by Ken Fitlike; 05-02-2006 at 08:30 AM. Reason: typo
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    Mad OnionKnight's Avatar
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    Code:
    #include <stdio.h>
    
    #define SIX  1+5
    #define NINE 8+1
    
    int main ()
    {
        printf("%d times %d equals %d", SIX, NINE, SIX*NINE);
        return 0;
    }

  9. #9
    and the hat of wrongness Salem's Avatar
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    > printf("%d times %d equals %d", SIX, NINE, SIX*NINE);
    I wonder what this will print.
    A demonstration of the precedence traps which can happen with macros no doubt
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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