LNK2005 object already defined error (Not a library conflict)

This is a discussion on LNK2005 object already defined error (Not a library conflict) within the C Programming forums, part of the General Programming Boards category; Greetings, I'm getting an error in my code where I include a header file in more than one location and ...

  1. #1
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    LNK2005 object already defined error (Not a library conflict)

    Greetings, I'm getting an error in my code where I include a header file in more than one location and I get the LNK2005 error during linking. I know that in C a code block is needed around the header file so that it is only included once but I forgot what that code block looks like (I'm used to C++ where this problem doesn't occur).

    Isn't it something like?
    Code:
    #ifndef HEADER
    #define HEADER
    //header code
    //more header code
    #ifdef HEADER
    #endif HEADER
    Am I close? It's been a while

  2. #2
    CSharpener vart's Avatar
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    Code:
    #ifndef HEADER_H
    #define HEADER_H
    //header code
    
    
    
    #endif //HEADER_H
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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    Hmm, I tried that and I'm still getting the errors. Is there anything else I need?

  4. #4
    ZuK
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    Header guards don't protect against linker errors.
    Guess you defined some variable or function in the header. Headers should only contain declarations.
    Kurt

  5. #5
    CSharpener vart's Avatar
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    post your header
    probably you define some variable or function in the header so linker has more than one instance of the same global object
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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    You're right, it is because I declare variables and functions inside the header file. Is there anyway around that linker error or do I have to remove the functions and variables?

    Yes I know it's bad coding practice to have functions in headers. I just want to know if it is possible.

  7. #7
    CSharpener vart's Avatar
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    you should move them to the c-file and leave only function declarations and externs for variables in the header
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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    Quote Originally Posted by vart
    you should move them to the c-file and leave only function declarations and externs for variables in the header
    Right, I know that's what I *should* do, I was wondering if I had any other options.

  9. #9
    Registered User whiteflags's Avatar
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    Not really.

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    Sigh, I hate C with a passion. Alright, thanks for the help.

  11. #11
    Just Lurking Dave_Sinkula's Avatar
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    Quote Originally Posted by maxhavoc
    Right, I know that's what I *should* do, I was wondering if I had any other options.
    I'm not trying to add insult to injury, but that's why folks should follow the shoulds from the get-go. Most often, the advice that we try to tuck away when we're new is exactly the stuff we should do immediately because we're new. Old timers merely try to prevent other folks from going through the same screwup cycle that we may have gone through.
    7. It is easier to write an incorrect program than understand a correct one.
    40. There are two ways to write error-free programs; only the third one works.*

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