weird problem with .h files

This is a discussion on weird problem with .h files within the C++ Programming forums, part of the General Programming Boards category; I just noticed that when you have a header file that declares variables, if you include it in another header ...

  1. #1
    Unregistered Leeman_s's Avatar
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    weird problem with .h files

    I just noticed that when you have a header file that declares variables, if you include it in another header file, it tries to declare the variables twice which gives redefinition errors. I discovered this trying to get my project to work. It compiles, but here are the errors:

    Code:
    Compiling...
    main.cpp
    Ship.cpp
    Linking...
    Ship.obj : error LNK2005: "struct HBITMAP__ * shipmask" (?shipmask@@3PAUHBITMAP__@@A) already defined in main.obj
    Ship.obj : error LNK2005: "struct HBITMAP__ * shipvar" (?shipvar@@3PAUHBITMAP__@@A) already defined in main.obj
    Ship.obj : error LNK2005: "struct SHIP player" (?player@@3USHIP@@A) already defined in main.obj
    Debug/Windows Tutorial.exe : fatal error LNK1169: one or more multiply defined symbols found
    Error executing link.exe.
    
    Windows Tutorial.exe - 4 error(s), 0 warning(s)
    Attached Files Attached Files

  2. #2
    moi
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    its not like this has been posted ONE FRICKING MILLION TIMES BEFORE, but do this with each of your header files:

    Code:
    ==========foobar.h=============
    #ifndef FOOBAR_HEADER_FILE
    #define FOOBAR_HEADER_FILE
    
    // put everything else here
    
    #endif
    next time try a search, eh?
    hello, internet!

  3. #3
    Unregistered Leeman_s's Avatar
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    Thank you vVv. I got it to work, however still don't understand why I need to do this. Would you be able to explain this or redirect me to somewhere else that can?
    Last edited by Leeman_s; 12-22-2002 at 05:14 PM.

  4. #4
    Unregistered Leeman_s's Avatar
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    Wow, very nice! This has just opened up a whole new level of program organization! Now I don't need any functions declared in main.cpp except the windows ones. Thanks again vVv.

  5. #5
    S Sang-drax's Avatar
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    Hehe, wouldn't it be convenient to learn basic C++ programming before learning game development?
    Last edited by Sang-drax : Tomorrow at 02:21 AM. Reason: Time travelling

  6. #6
    Unregistered Leeman_s's Avatar
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    Well, it's sorta hard to learn the regular way when you don't take any c++ classes and just learn on your own.

    lol, this is how it went for me. I bought MSVC++, only knew how to program in BASIC. Talk about a huge change in compiler level of difficulty, if you will. All I had to learn was the compiler, my book, and the internet.

  7. #7
    S Sang-drax's Avatar
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    Originally posted by Leeman_s
    Well, it's sorta hard to learn the regular way when you don't take any c++ classes and just learn on your own.
    I have acquired like 1% of my skill in C++ though classes, the rest I've studied on my own.
    I borrow books and read them - IMO a very good way to learn programming.
    Last edited by Sang-drax : Tomorrow at 02:21 AM. Reason: Time travelling

  8. #8
    Unregistered Leeman_s's Avatar
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    sang is that website yours? in your sig.

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