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Thread: Undefined reference to my signal

  1. #1
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    Unhappy Undefined reference to my signal

    Hi!
    This is my first post so I'd like to say hello everyone!
    I am trying to compile my simple project, but I get an error:
    Qt Code:
    1. release\fetchThread.o(.text+0x387):fetchThread.cpp: undefined reference to `FetchThread::log(QString)'
    2. release\fetchThread.o(.text+0x3ba):fetchThread.cpp: undefined reference to `FetchThread::connected()'
    3. collect2: ld returned 1 exit status
    4. mingw32-make[1]: *** [release\project.exe] Error 1
    To copy to clipboard, switch view to plain text mode 
    FetchThread::log(QString) and FetchThread::connected(void) are my own signals defined in the appropriate header file.
    Files:
    PROJECT DIRECTORY
    WRONG CPP
    WRONG H
    It complains about my signals emitted from the above CPP file.
    Please help
    Regards,
    Tomek

  2. #2
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    Default Re: Undefined reference to my signal

    It looks like make didn't run moc program on your fetchThread.h file. Run qmake (without any parameters) to generate new Makefiles and try compiling your project again.

  3. #3
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    Default Re: Undefined reference to my signal

    Add HEADERS+=fetchThread.h to your .pro file.

  4. #4
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    Thumbs up Re: Undefined reference to my signal

    Thank you! It works now.
    First I added the HEADERS directive and then generated new Makefiles.
    Happy New Year

  5. #5
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    Red face Re: Undefined reference to my signal

    I can't tell you how many times I have been banging my head on the desk asking myself "why isn't this compiling?!?" then realizing I need to run qmake again because I added another file to the project since last time I ran it.
    (of course this is AFTER I go through all of the source code, like, 5 times lol)

    Katrina

  6. #6
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    Default Re: Undefined reference to my signal

    AFAIK. If you add a file then make calls qmake first. Only when u add Q_OBJECT to the class do we need to call the qmake manually.
    We can't solve problems by using the same kind of thinking we used when we created them

  7. The following user says thank you to sunil.thaha for this useful post:

    PstdEr (23rd July 2013)

  8. #7
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    Default Re: Undefined reference to my signal

    btw, there is a strange symbol (single quote) after "HEADERS" in the project file

  9. #8
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    Wink Re: Undefined reference to my signal

    I found the apostrophe too, happily quickly
    I've been always executing `qmake && make` not to forget about the qmake.
    Thanks for your posts!

  10. #9
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    Smile Re: Undefined reference to my signal

    Quote Originally Posted by sunil.thaha
    Only when u add Q_OBJECT to the class do we need to call the qmake manually.
    This is good to know, I have been trying to run it after I add any new file regardless of of it Q_OBJECT-ed-ness. (although I tend to implement signals and slots heavily(maybe too much so!), so 80% of my new code is a Q_OBJECT...still good info!!! Thanks!)

    Katrina

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    Default Re: Undefined reference to my signal

    Missing Q_OBJECT in the class declaration also does lead to the same error: undefined reference to `MyThread::MySignal()'

  12. The following user says thank you to TheIndependentAquarius for this useful post:

    PstdEr (23rd July 2013)

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