Linking Files

This is a discussion on Linking Files within the C++ Programming forums, part of the General Programming Boards category; Getting an error when linking files "one or more multiply defined symbols found" i am linking a cpp file and ...

  1. #1
    Registered User
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    Unhappy Linking Files

    Getting an error when linking files
    "one or more multiply defined symbols found"
    i am linking a cpp file and header file and inside my header file
    i have #ifndef
    #define
    ...code
    #endif

    Anyone have a solution???

  2. #2
    Mad OnionKnight's Avatar
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    Conflicting identifiers I guess. Check if you have any variables/function named the same as another.

  3. #3
    Devil's Advocate SlyMaelstrom's Avatar
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    Is it simply:
    Code:
    #ifndef
    #define
    
    /* Code here */
    
    #endif
    or do you have an identifier for what you're defining?
    Code:
    #ifndef MY_LIB_H
    #define MY_LIB_H
    
    #endif
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  4. #4
    Guest Sebastiani's Avatar
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    i have #ifndef
    #define
    ...code
    #endif
    I'm assuming by that you mean you have something like this:

    Code:
    #ifndef SOMECLASS_HEADER_H
    #define SOMECLASS_HEADER_H
    /* code */
    #endif
    Code:
    #include <cmath>
    #include <complex>
    bool euler_flip(bool value)
    {
        return std::pow
        (
            std::complex<float>(std::exp(1.0)), 
            std::complex<float>(0, 1) 
            * std::complex<float>(std::atan(1.0)
            *(1 << (value + 2)))
        ).real() < 0;
    }

  5. #5
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    yes i have #ifndef SOME_HEADER_H
    #define SOME HEADER_H

  6. #6
    Guest Sebastiani's Avatar
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    then are there multiple headers enclosed in the same identifier SOME_HEADER_H?
    Code:
    #include <cmath>
    #include <complex>
    bool euler_flip(bool value)
    {
        return std::pow
        (
            std::complex<float>(std::exp(1.0)), 
            std::complex<float>(0, 1) 
            * std::complex<float>(std::atan(1.0)
            *(1 << (value + 2)))
        ).real() < 0;
    }

  7. #7
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    Nope. I was reading around aparantly MSVS has this problem alot.
    "one or more multiply defined symbols found"...

  8. #8
    Guest Sebastiani's Avatar
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    odd. try it with another compiler and see if the results are the same...
    Code:
    #include <cmath>
    #include <complex>
    bool euler_flip(bool value)
    {
        return std::pow
        (
            std::complex<float>(std::exp(1.0)), 
            std::complex<float>(0, 1) 
            * std::complex<float>(std::atan(1.0)
            *(1 << (value + 2)))
        ).real() < 0;
    }

  9. #9
    Just Lurking Dave_Sinkula's Avatar
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    Quote Originally Posted by MT_Pockets
    i have #ifndef
    #define
    ...code
    #endif
    Hopefully by "...code" you don't mean code, but instead merely delcarations and such. Definitions of functions and data must done exactly once.
    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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