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Thread: "Undefined reference to" error

  1. #1

    Default "Undefined reference to" error

    Good morning to everyone.
    First of all, I work in Linux Ubuntu 8.04 with Eclipse and Qt integration.
    I'm making a qt gui project named "rezclient". In my project I have to use some c functions of a library (librezShared.a) and other c functions declared in "rezCltProtocol.h" and defined in "rezCltProtocol.c". I have no problem with the library, but I have the error "undefined reference to" the functions of the rezCltProtocol.h file.

    - This is the message of console:

    "make debug
    make -f Makefile.Debug
    make[1]: Entering directory `/home/francesco/Scrivania/SERVER/eclipseWorkspace/rezclient'
    g++ -Wl,-rpath,/usr/local/Trolltech/Qt-4.4.3/lib -o rezclient debug/main.o debug/rezclient.o debug/moc_rezclient.o -L/usr/local/Trolltech/Qt-4.4.3/lib -lrezShared -L/home/francesco/Scrivania/SERVER/sharedSrc/Debug -lQtGui -L/usr/local/Trolltech/Qt-4.4.3/lib -L/usr/X11R6/lib -lXext -lX11 -lQtCore -lz -lm -lrt -ldl -lpthread
    debug/rezclient.o: In function `rezclient:n_pushButton_clicked()':
    make[1]: Leaving directory `/home/francesco/Scrivania/SERVER/eclipseWorkspace/rezclient'
    /home/francesco/Scrivania/SERVER/eclipseWorkspace/rezclient/rezclient.cpp:34: undefined reference to `execCmdHeartbeat(int, unsigned int, double*)'
    /home/francesco/Scrivania/SERVER/eclipseWorkspace/rezclient/rezclient.cpp:35: undefined reference to `execCmdGetClients(int, unsigned int, tRezClientList*)'
    collect2: ld returned 1 exit status
    make[1]: *** [rezclient] Error 1
    make: *** [debug] Error 2"

    - This is my .pro file:

    TEMPLATE = app
    TARGET = rezclient
    QT += core \

    # Input
    HEADERS += rezclient.h
    SOURCES += main.cpp \
    FORMS += rezclient.ui
    INCLUDEPATH += /home/francesco/Scrivania/SERVER/sharedSrc; \
    LIBS += -lrezShared \

    And in my code I use this instructions to include the headers files:

    extern "C"{
    #include "../../sharedSrc/commondefs.h"
    #include "../../sharedSrc/rezProtocol.h"
    #include "../../sharedSrc/tcpsocket.h"
    #include "../../rezClient/src/rezCltProtocol.h"

    I really don't know how to solve this problem. I hope you'll help me.
    Good morning.

    Ps. Excuse me for my english.
    Last edited by f.tristano; 2nd February 2009 at 08:54.

  2. #2
    Join Date
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    Oslo, Norway
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    Default Re: "Undefined reference to" error

    Where are execCmdHeartbeat() and execCmdGetClients() implemented?
    J-P Nurmi

  3. #3
    Join Date
    Dec 2006
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    Default Re: "Undefined reference to" error

    two possible errors:

    * either those two functions are C (not C++!) functions: then the header was included in some C++ file without the extern "C"
    (You can see that those function-calls where compiled as C++ function calls because they have signature. C-calls are just a function name (no argument types).)

    * those really are C++ functions and you just do not link the lib or object file that contains them


  4. #4

    Default Re: "Undefined reference to" error

    Reply to jpn:
    The two functions are implemented in my rezclient.cpp file (I attached the file).

    Reply to caduel:
    the two functions are C functions and I included them with extern C
    Attached Files Attached Files

  5. #5

    Default Re: "Undefined reference to" error

    I solved.
    I just added in my .pro file the source file rezCltProtocol.c.
    However, thanks.

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