Qt and dlib in ubuntu linking problem

Jimmy32

Hi Guys,
I have installed dlib in my pc with the following command:

wget http://dlib.net/files/dlib-19.10.tar.bz2
tar xvf dlib-19.10.tar.bz2
cd dlib-19.10/
mkdir build
cd build
cmake ..
cmake --build . --config Release
sudo make install
sudo ldconfig
cd ..

and then in my Qt project in the Qmake.pro i have link to the library with pkg-config with this line:

PKGCONFIG += dlib-1

but after build the project i got some errors but i am lost...

Here are some of the errors:

/usr/local/include/dlib/test_for_odr_violations.h:24: error: undefined reference to `USER_ERROR__inconsistent_build_configuration__see_dlib_faq_1_'

/usr/local/include/dlib/test_for_odr_violations.h:51: error: undefined reference to `DLIB_VERSION_MISMATCH_CHECK__EXPECTED_VERSION_19_10_0'

Hope guys can help me.
Thank you

SGaist

Hi,

From the FAQ pointed to by the error message, I understand it as you are mixing debug and release builds. You should build dlib for both and then linked to the correct version based on which mode you build your application with.

Jimmy32

@SGaist Thank you for your answer.
Indeed in Qtcreator i changed the debug mode to release mode and the errors are gone but if i understand well your answer,
should i reinstall dlib but this time with debug mode? something like that

cd dlib-19.10/
mkdir build
cd build
cmake ..
cmake --build . --config Debug
sudo make install
sudo ldconfig
cd ..

Do the created libraries will be different?

Thanks a lot

SGaist

Yes, a debug build contains all the debug symbols, has usually less optimisations, might assert if certains conditions are not met, might log what happens etc.

Jimmy32

@SGaist Thank you for your help but after build the Qt project as release to fit my dlib build i got another problem.
If there is no dlib deep learning network defined in my code, i can build but once i add a dlib network, i got a building error

 /home/jimmy/Desktop/Connected_Robotics_Watson/workco/work/mainWindow.cpp:-1: error: undefined reference to `dlib::cpu::pooling::pooling()'

i am lost... because in a normal cpp code compile with cmake, everything worked well.

Thanks,

jsulm

@Jimmy32 You're not linking dlib.
Try with LIBS/INCLUDEPATH in pro file instead of PKGCONFIG. See http://doc.qt.io/qt-5/qmake-variable-reference.html

Jimmy32

@jsulm Thank you
i have tried this before, i added the lib in the LIBS -ldlib but i got another error

:-1: error: /usr/local/lib/libdlib.a(cpu_dlib.cpp.o): undefined reference to symbol 'cblas_sscal'

...

jsulm

@Jimmy32 Can you show your pro file?
Does the dlib depend on other libraries (you can check with ldd)?

Jimmy32

@jsulm my .pro file:

QT += network
QT += widgets
TEMPLATE = app
TARGET = Connected


INCLUDEPATH += /usr/local/include
LIBS += -L /usr/local/lib -lopencv_core -lopencv_imgproc -lopencv_highgui -lopencv_videoio -lopencv_imgcodecs -ldlib
QMAKE_CXXFLAGS += -std=c++11
# PKGCONFIG = dlib-1


# Input
HEADERS += mainWindow.hpp
SOURCES += main.cpp mainWindow.cpp

and for ldd i dont have the executable as it cant build...

jsulm

@Jimmy32 Remove space between -L and /usr/local/lib
You don't need the executable. What I meant is:

ldd /usr/local/lib/dlib.so

Jimmy32

@jsulm my library is static and i typed

ldd /usr/local/lib/libdlib.a

but it gave me " not a dynamic executable "

jsulm

@Jimmy32 Did you remove the space? Don't forget to run qmake afterwards.

Jimmy32

@jsulm yes i did remove but still the same

jsulm

@Jimmy32 My guess is that dlib depends on some other libs you're currently not linking

Jimmy32

@jsulm after some search, dlib depends on pthread and x11

Eyyup

dlib installation and Qt - dlib linking
https://www.youtube.com/watch?v=YkTHq65FPa4