Thread: Forward declaration with g++

  1. 06-15-2009 #1
    blakaxe
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    Forward declaration with g++

    In class filter.h, I have the following forward declarations

    template<class T> //Forward declaration due to circular dependency
    class Agc;
    class FixPt;
    class QuantizerCmplx;
    template<class T>
    class Quantizer;

    I get the following errors while compiling with g++.

    ../source/filter.h: In member function âint FarrowFilter<T>::filter_quantize()â:
    ../source/filter.h:1837: error: invalid use of undefined type âstruct QuantizerCmplxâ
    ../source/filter.h:12: error: forward declaration of âstruct QuantizerCmplxâ

    How do I solve this problem? It compiles fine with VC++

    Thanks
  2. 06-15-2009 #2
    legit
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    Please use code tags. It makes your post so much easier to read.
    Last edited by legit; 06-15-2009 at 09:48 AM.
  3. 06-15-2009 #3
    Salem
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    Lemme guess, rather than insert [code][/code] tags, you decided to do the bone-headed thing and remove all the braces instead, just to stop the board complaining at you.

    Great, now what you posted it utterly meaningless.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  4. 06-15-2009 #4
    anon
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    It basically says that there is something on line 1837 that requires the full definition of QuantizerCmplx for which a forward declaration alone is not enough.
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).
  5. 06-17-2009 #5
    Angus
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    The last time I tried to forward declare a template class I failed. I'll bet it has something to do w/that.
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