Strange Linking Error

mcosta

I cannot see anymore your original post, what was the error??

DRoscoe

I am getting what looks like a typical "unresolved external" error that defies my attempts at resolving. Unlike several others I have already fixed, this one has a bit of information that is not normal:

aop_interface.lib(FmcIntentWaypoint.obj):-1: error: LNK2001: unresolved external symbol "public: static class dna::Repository * __cdecl ACE_Unmanaged_Singleton<class dna::Repository,class ACE_Recursive_Thread_Mutex>::instance(void)" (?instance@?$ACE_Unmanaged_Singleton@VRepository@dna@@VACE_Recursive_Thread_Mutex@@@@SAPAVRepository@dna@@XZ)

The above looks normal, but after this error, there is an additional line:

File not found: aop_interface.lib(FmcIntentWaypoint.obj)

I believe this is a clue as to why I can't resolve this problem. I looked in the DEBUG folder for the project and I do see the file in question.

Any idea what's going on?

mcosta

Where aop_interface.lib is defined and built? and where is linked?

DRoscoe

The main SUBDIRS project builds the library:

CONFIG += c++11 ordered
TEMPLATE = subdirs

SUBDIRS +=
aop_logger
aop_xml
aop_serial
aop_util
aop_measure
MathUtilities
DataCollection
DebugLogger
MoreMath
AvionicsBus
AircraftDataModel
WindModel
TableLookups
configuration
dna
aop_data
aop_comm
tap_data
AtosUtils
tap_messaging
BufferedSharedMemory
RouteContainer
aop_interface
tap_new_display_app

It is linked in the main application subproject:

include(../top_srcdir.pri) # defines top-level source trees
include(../ace_lib.pri) # defines ACE library
include(../tap_data.pri) # defines tap_data library
include(../tap_messaging.pri) # defines tap_messaging library

QT += qml quick widgets
INCLUDEPATH = $$aop_util_includes
$$aop_logger_includes
$$tap_data_includes
$$aop_serial_includes
$$tap_messaging_includes
$$aop_data_includes
$$aop_measure_includes
$$aop_interface_includes
$$aop_xml_includes
include(../ace_path.pri)
include(../dna.pri)
include(../aop_logger.pri)
include(../aop_interface.pri)
include(../aop_util.pri)
include(../aop_xml.pri)
include(../aop_serial.pri)
include(../aop_measure.pri)
include(../AvionicsBus.pri)
SOURCES += $$files(.cpp)
HEADERS += $$files(.hpp)

RESOURCES += qml.qrc

QML_IMPORT_PATH =

include(deployment.pri)

mcosta

Is it possible to show the LIBS contents while building??

Could be also a dependency problem, are your libraries static or dynamic?

DRoscoe

I will instrument the files to get the output you request. The libraries are all static.

mcosta

@DRoscoe said:

The libraries are all static.

IIRC Static libraries need to be linked in the right order. This means that if the library libA uses objects of library libB you have to link in sequence -lB -lA.

DRoscoe

What is the best way to ensure proper linking order? Should it be handled on a per library basis? For example, MY_APP relies on library MY_LIB. MY_LIB relies on LIBa, LIBb and LIBc in that order. Should I enforce linking at MY_LIB so that MY_APP only needs to link MY_LIB, or should MY_APP link LIBa, LIBb, LIBc and then MY_LIB?

DRoscoe

OK, I went through each project and cleaned up the dependencies and now the project builds and runs. It crashes, but that's a problem with my functional code.

I would still like to know what the best way to handle library dependencies is WRT static libraries because a lack of understanding will just lead to repeat problems later, if I change the project around. I don't have this problem when I build my project outside of Qt Creator/qmake. On the Windows side, I use cmake to create the project files and I am intimately familiar with how to work with it. I am new to Qt Creator/qmake, so I am making a lot of mistakes. I need to learn this, though, since I also need to build for MacOS and iOS and I am using qmake to generate the xCode project files.

Thank you for your help!

mcosta

@DRoscoe said:

Should I enforce linking at MY_LIB so that MY_APP only needs to link MY_LIB

Honestly I don't know if all platforms/compilers support it.