Linker error when calling a method of an external library

  • Hello,

    I'm trying to include an API for a hdmi frame grabber device in my project. The SDK is open source and can be downloaded here: (5,6 MB).

    I've put the contents of the zip archive in my project folder:
    ➜ [frameGrabber] ls -al
    insgesamt 44K
    drwx------. 7 chris chris 4,0K 5. Jun 13:26 epiphan
    -rw-rw-r--. 1 chris chris 431 5. Jun 13:45 framegrabber.cpp
    -rw-rw-r--. 1 chris chris 467 5. Jun 13:44 framegrabber.h
    -rw-rw-r--. 1 chris chris 683 5. Jun 13:46
    -rw-rw-r--. 1 chris chris 18K 5. Jun 13:39
    -rw-rw-r--. 1 chris chris 1,8K 5. Jun 13:44 framegrabber.ui
    -rw-rw-r--. 1 chris chris 176 5. Jun 13:39 main.cpp

    Inside qtcreator, I used the option "add library" which added the following to my .pro-file:
    LIBS += -L$$PWD/epiphan/frmgrab/lib/linux/x86_64/ -lfrmgrab
    INCLUDEPATH += $$PWD/epiphan/frmgrab/include
    INCLUDEPATH += $$PWD/epiphan/include
    DEPENDPATH += $$PWD/epiphan/frmgrab/include
    PRE_TARGETDEPS += $$PWD/epiphan/frmgrab/lib/linux/x86_64/libfrmgrab.a

    When I'm compiling my project at this point, no error occurs. Now, a button in the UI shall initialize the API. According to the documentation this is done by calling FrmGrabber_Init():
    void frameGrabber::on_pushButton_clicked()
    /* init epiphan sdk*/

    Unfortunately, this method call leads to this linker error:
    13:58:48: Starte "/usr/bin/make"
    /usr/bin/qmake-qt4 -spec /usr/lib64/qt4/mkspecs/linux-g++ CONFIG+=debug CONFIG+=declarative_debug -o Makefile ../frameGrabber/
    g++ -c -pipe -g -Wall -W -D_REENTRANT -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -I/usr/lib64/qt4/mkspecs/linux-g++ -I../frameGrabber -I/usr/include/QtCore -I/usr/include/QtGui -I/usr/include -I../frameGrabber/epiphan/frmgrab/include -I../frameGrabber/epiphan/include -I. -I. -I../frameGrabber -I. -o framegrabber.o ../frameGrabber/framegrabber.cpp
    g++ -o frameGrabber main.o framegrabber.o moc_framegrabber.o -L/usr/lib64 -L/home/chris/frameGrabber/epiphan/frmgrab/lib/linux/x86_64/ -lfrmgrab -lQtGui -lQtCore -lpthread
    /home/chris/frameGrabber/epiphan/frmgrab/lib/linux/x86_64//libfrmgrab.a(frmgrab.o): In function FrmGrab_CommonInit': frmgrab.c:(.text+0x40): undefined reference toCS_Init'
    frmgrab.c:(.text+0x63): undefined reference to hashFreeValueProc' frmgrab.c:(.text+0x75): undefined reference toHASH_Init'
    frmgrab.c:(.text+0x94): undefined reference to CS_Destroy' /home/chris/frameGrabber/epiphan/frmgrab/lib/linux/x86_64//libfrmgrab.a(frmgrab.o): In functionFrmGrab_CommonDestroy':
    frmgrab.c:(.text+0xa9): undefined reference to CS_Destroy' [...] frmgrab.c:(.text+0xe34): undefined reference toMEM_Free'
    collect2: error: ld returned 1 exit status
    make: *** [frameGrabber] Error 1
    13:58:50: Der Prozess "/usr/bin/make" wurde mit dem Rückgabewert 2 beendet.
    Fehler beim Erstellen/Deployment des Projekts frameGrabber(Kit: Desktop)

    Even if I assume that only very few people here have ever used this SDK before, I wonder if anyone could help me. Did I choose the correct way of including an external library or did I make a mistake? Do you have any idea why this failes?


  • Hi,
    If you want to include the libraries static, both the library and your program needs to be compiled with the same compiler and version!
    Otherwise you need the QLibrary class to do a dynamic include.

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