Undefined reference, altough references in library exists

kkettinger

Hello,

i have some strange reoccouring linker error which i can't track down. The last time i had this error it somehow disappeared after deleting the *.pro.user file, but this time, it just keeps reappearing.

My subdirs pro file:

TEMPLATE = subdirs

common.subdir = src/common
common.target = sub-src-common

atctrl.subdir = src/atctrl
atctrl.target = sub-src-atctrl
atctrl.depends = common

app.subdir = src/app
app.target = sub-src-app
app.depends = common atctrl

SUBDIRS = common atctrl app

The pro file for the app project:

QT += quick

CONFIG += c++17 static

DEFINES += QT_DEPRECATED_WARNINGS
DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000
DEFINES += QT_MESSAGELOGCONTEXT

QT += serialport

INCLUDEPATH += $$PWD/src

SOURCES += \
        src/main.cpp

#HEADERS += 

TARGET = app

# common
win32:CONFIG(release, debug|release): LIBS += -L$$OUT_PWD/../common/release/ -lcommon
else:win32:CONFIG(debug, debug|release): LIBS += -L$$OUT_PWD/../common/debug/ -lcommon
else:unix:!macx: LIBS += -L$$OUT_PWD/../common/ -lcommon

INCLUDEPATH += $$PWD/../common
DEPENDPATH += $$PWD/../common

win32-g++:CONFIG(release, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../common/release/libcommon.a
else:win32-g++:CONFIG(debug, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../common/debug/libcommon.a
else:win32:!win32-g++:CONFIG(release, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../common/release/common.lib
else:win32:!win32-g++:CONFIG(debug, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../common/debug/common.lib
else:unix:!macx: PRE_TARGETDEPS += $$OUT_PWD/../common/libcommon.a

# atctrl
win32:CONFIG(release, debug|release): LIBS += -L$$OUT_PWD/../atctrl/release/ -latctrl
else:win32:CONFIG(debug, debug|release): LIBS += -L$$OUT_PWD/../atctrl/debug/ -latctrl
else:unix:!macx: LIBS += -L$$OUT_PWD/../atctrl/ -latctrl
INCLUDEPATH += $$PWD/../atctrl
DEPENDPATH += $$PWD/../atctrl
win32-g++:CONFIG(release, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../atctrl/release/libatctrl.a
else:win32-g++:CONFIG(debug, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../atctrl/debug/libatctrl.a
else:win32:!win32-g++:CONFIG(release, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../atctrl/release/atctrl.lib
else:win32:!win32-g++:CONFIG(debug, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../atctrl/debug/atctrl.lib
else:unix:!macx: PRE_TARGETDEPS += $$OUT_PWD/../atctrl/libatctrl.a

The pro file for the atctrl library:

QT -= gui

TEMPLATE = lib
CONFIG += c++17 staticlib

DEFINES += QT_DEPRECATED_WARNINGS
DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000
DEFINES += QT_MESSAGELOGCONTEXT

SOURCES += \
    atctrl/atctrl.cpp

HEADERS += \
    atctrl/atctrl.h
    
QT += serialport

# common
win32:CONFIG(release, debug|release): LIBS += -L$$OUT_PWD/../common/release/ -lcommon
else:win32:CONFIG(debug, debug|release): LIBS += -L$$OUT_PWD/../common/debug/ -lcommon
else:unix:!macx: LIBS += -L$$OUT_PWD/../common/ -lcommon

INCLUDEPATH += $$PWD/../common
DEPENDPATH += $$PWD/../common

win32-g++:CONFIG(release, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../common/release/libcommon.a
else:win32-g++:CONFIG(debug, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../common/debug/libcommon.a
else:win32:!win32-g++:CONFIG(release, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../common/release/common.lib
else:win32:!win32-g++:CONFIG(debug, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../common/debug/common.lib
else:unix:!macx: PRE_TARGETDEPS += $$OUT_PWD/../common/libcommon.a

The pro file for the common library:

QT -= gui

TEMPLATE = lib
CONFIG += c++17 staticlib

DEFINES += QT_DEPRECATED_WARNINGS
DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000
DEFINES += QT_MESSAGELOGCONTEXT

SOURCES += \
    common/serial_base/serial_base.cpp

HEADERS += \
    common/serial_base/serial_base.h 

QT += serialport

!isEmpty(target.path): INSTALLS += target

In the atctrl library there is the class ATCtrl::cATCtrl which derives from SerialBase::cSerialBase from the common library.

In the app project i'm using the ATCtrl::cATCtrl class. So the dependency goes like app (project) -> atrctrl (staticlib) -> common (staticlib).

When i'm building the app project, i get this linker error:

The complete error log:

<build_debug>/src/atctrl/debug/libatctrl.a(atctrl.o): In function `ATCtrl::cATCtrl::~cATCtrl()':
<build_debug>\src\atctrl/../../../keyboard/src/atctrl/atctrl/atctrl.h:42: undefined reference to `SerialBase::cSerialBase::~cSerialBase()'
<build_debug>/src/atctrl/debug/libatctrl.a(atctrl.o): In function `ATCtrl::cATCtrl::cATCtrl(QObject*)':
<build_debug>\src\atctrl/../../../keyboard/src/atctrl/atctrl/atctrl.cpp:48: undefined reference to `SerialBase::cSerialBase::cSerialBase(QObject*)'
<build_debug>\src\atctrl/../../../keyboard/src/atctrl/atctrl/atctrl.cpp:48: undefined reference to `SerialBase::cSerialBase::~cSerialBase()'
<build_debug>/src/atctrl/debug/libatctrl.a(atctrl.o): In function `ATCtrl::cATCtrl::init(QString)':
<build_debug>\src\atctrl/../../../keyboard/src/atctrl/atctrl/atctrl.cpp:64: undefined reference to `SerialBase::cSerialBase::open(QString)'
<build_debug>/src/atctrl/debug/libatctrl.a(atctrl.o): In function `ATCtrl::cATCtrl::disableLocalEcho()':
<build_debug>\src\atctrl/../../../keyboard/src/atctrl/atctrl/atctrl.cpp:132: undefined reference to `SerialBase::cSerialBase::handleRequest(QString const&, QString const&, QStringList&)'
<build_debug>/src/atctrl/debug/libatctrl.a(atctrl.o): In function `ATCtrl::cATCtrl::AT()':
<build_debug>\src\atctrl/../../../keyboard/src/atctrl/atctrl/atctrl.cpp:148: undefined reference to `SerialBase::cSerialBase::handleRequest(QString const&, QString const&, QStringList&)'
<build_debug>/src/atctrl/debug/libatctrl.a(atctrl.o): In function `ATCtrl::cATCtrl::enableGPS(bool)':
<build_debug>\src\atctrl/../../../keyboard/src/atctrl/atctrl/atctrl.cpp:164: undefined reference to `SerialBase::cSerialBase::handleRequest(QString const&, QString const&, QStringList&)'
<build_debug>/src/atctrl/debug/libatctrl.a(atctrl.o): In function `ATCtrl::cATCtrl::resetGPS(int)':
<build_debug>\src\atctrl/../../../keyboard/src/atctrl/atctrl/atctrl.cpp:182: undefined reference to `SerialBase::cSerialBase::handleRequest(QString const&, QString const&, QStringList&)'
<build_debug>/src/atctrl/debug/libatctrl.a(atctrl.o): In function `ATCtrl::cATCtrl::getGPSStatus(int)':
<build_debug>\src\atctrl/../../../keyboard/src/atctrl/atctrl/atctrl.cpp:199: undefined reference to `SerialBase::cSerialBase::handleRequest(QString const&, QString const&, QStringList&)'
<build_debug>/src/atctrl/debug/libatctrl.a(atctrl.o):<build_debug>\src\atctrl/../../../keyboard/src/atctrl/atctrl/atctrl.cpp:217: more undefined references to `SerialBase::cSerialBase::handleRequest(QString const&, QString const&, QStringList&)' follow
<build_debug>/src/atctrl/debug/libatctrl.a(moc_atctrl.o): In function `ATCtrl::cATCtrl::qt_metacast(char const*)':
<build_debug>\src\atctrl/debug/moc_atctrl.cpp:221: undefined reference to `SerialBase::cSerialBase::qt_metacast(char const*)'
<build_debug>/src/atctrl/debug/libatctrl.a(moc_atctrl.o): In function `ATCtrl::cATCtrl::qt_metacall(QMetaObject::Call, int, void**)':
<build_debug>\src\atctrl/debug/moc_atctrl.cpp:226: undefined reference to `SerialBase::cSerialBase::qt_metacall(QMetaObject::Call, int, void**)'
<build_debug>/src/atctrl/debug/libatctrl.a(moc_atctrl.o):moc_atctrl.cpp:(.rdata+0x620): undefined reference to `SerialBase::cSerialBase::staticMetaObject'

The linker command which fails is the following (i replaced the build dir with <build_debug>):

g++ -Wl,-subsystem,windows -mthreads -o debug/app.exe debug/main.o debug/backend.o debug/moc_backend.o  -L"<build_debug>/src/common/debug" -lcommon -L"<build_debug>/src/atctrl/debug" -latctrl D:/Qt/5.14.2/mingw73_64/lib/libQt5Quick.a D:/Qt/5.14.2/mingw73_64/lib/libQt5Gui.a D:/Qt/5.14.2/mingw73_64/lib/libQt5QmlModels.a D:/Qt/5.14.2/mingw73_64/lib/libQt5Qml.a D:/Qt/5.14.2/mingw73_64/lib/libQt5Network.a D:/Qt/5.14.2/mingw73_64/lib/libQt5SerialPort.a D:/Qt/5.14.2/mingw73_64/lib/libQt5Core.a  -lmingw32 D:/Qt/5.14.2/mingw73_64/lib/libqtmain.a -LC:/openssl/lib -LC:/Utils/my_sql/mysql-5.7.25-winx64/lib -LC:/Utils/postgresql/pgsql/lib -lshell32

The two static libraries are included (-lcommon -latctrl) in the linker command.

Now when i'm looking into libcommon.a with nm (nm -A -C libcommon.a), i can find all the references which the linker says it is not finding it:

<...>
libcommon.a:serial_base.o:000000000000014c T SerialBase::cSerialBase::open(QString)
libcommon.a:serial_base.o:0000000000000f16 T SerialBase::cSerialBase::close()
<...>
libcommon.a:serial_base.o:0000000000000088 T SerialBase::cSerialBase::cSerialBase(QObject*)
libcommon.a:serial_base.o:0000000000000088 T SerialBase::cSerialBase::cSerialBase(QObject*)
libcommon.a:serial_base.o:000000000000005e T SerialBase::cSerialBase::~cSerialBase()
libcommon.a:serial_base.o:0000000000000000 T SerialBase::cSerialBase::~cSerialBase()
libcommon.a:serial_base.o:0000000000000000 T SerialBase::cSerialBase::~cSerialBase()

What am i missing?

Qt Creator Version 4.12.0
Qt 5.14.2 (mingw730_64)

I appreciate any help here, thanks.

Best regards,
Kevin

Christian Ehrlicher

The link order is wrong, -lactrl must come first,s ee also e.g. here

jsulm

@kkettinger said in Undefined reference, altough references in library exists:

g++ -Wl,-subsystem,windows -mthreads -o debug/app.exe debug/main.o debug/backend.o debug/moc_backend.o -L"<build_debug>/src/common/debug" -lcommon -L"<build_debug>/src/atctrl/debug" -latctrl D:/Qt/5.14.2/mingw73_64/lib/libQt5Quick.a D:/Qt/5.14.2/mingw73_64/lib/libQt5Gui.a D:/Qt/5.14.2/mingw73_64/lib/libQt5QmlModels.a D:/Qt/5.14.2/mingw73_64/lib/libQt5Qml.a D:/Qt/5.14.2/mingw73_64/lib/libQt5Network.a D:/Qt/5.14.2/mingw73_64/lib/libQt5SerialPort.a D:/Qt/5.14.2/mingw73_64/lib/libQt5Core.a -lmingw32 D:/Qt/5.14.2/mingw73_64/lib/libqtmain.a -LC:/openssl/lib -LC:/Utils/my_sql/mysql-5.7.25-winx64/lib -LC:/Utils/postgresql/pgsql/lib -lshell32

The paths look strange: -L"<build_debug>/src/common/debug" -lcommon -L"<build_debug>/src/atctrl/debug"
What is <build_debug>?
Also, if common is a static lib when your pro file is wrong as you are linking dynamically.

kkettinger

I have replaced the build-dir with <build_debug>, the original path is:

D:/Dev/project01/src/build-subdirs-Desktop_Qt_5_14_2_MinGW_64_bit-Debug/

@jsulm said in Undefined reference, altough references in library exists:

Also, if common is a static lib when your pro file is wrong as you are linking dynamically.

Why? I added "CONFIG += static" in the project pro-file, isn't that correct?

kkettinger

This is getting strange.. when i'm using SerialBase::cSerialBase (from common lib) directly in the app project (instantiating in main.cpp), suddenly the linker finds everything.

It seems like the linker doesn't find the dependency to SerialBase::cSerialBase (common lib) when only using ATCtrl::cATCtrl (atctrl lib).

Just for clarification, here the headers for the libraries:

common.pro:

class cSerialBase: public QObject
{
    Q_OBJECT
}

atctrl.pro:

class cATCtrl: public SerialBase::cSerialBase
{
    Q_OBJECT
}

Usage in app.pro (main.cpp) which doesn't work (linker doesn't find SerialBase::cSerialBase):

#include <atctrl/atctrl.h>

int main(int argc, char *argv[])
{
    ATCtrl::cATCtrl atctrl;
    return 0;
}

Usage in app.pro (main.cpp) which strangly does work:

#include <atctrl/atctrl.h>

int main(int argc, char *argv[])
{
    ATCtrl::cATCtrl atctrl;
    SerialBase::cSerialBase serialBase;
    return 0;
}

Christian Ehrlicher

The link order is wrong, -lactrl must come first,s ee also e.g. here

kkettinger

I switched the order in the app.pro file for the common and atctrl lib and now it works. Thank you very much.

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Solved Undefined reference, altough references in library exists