c++ - configuration of QT to code in book "opencv2 computer vision application programming cookbook" -

i teaching self book "opencv2 computer vision application programming cookbook" using qt creator 3.2.1 / qt 5.3.2 (clang5.0 (apple)). when tried build 1 program had warnings follows:

undefined symbols architecture x86_64:   "cv::imread(std::string const&, int)", referenced from:       mainwindow::on_pushbutton_clicked() in mainwindow.o       colordetectcontroller::setinputimage(std::string) in mainwindow.o   "cv::imshow(std::string const&, cv::_inputarray const&)", referenced from:       mainwindow::on_pushbutton_clicked() in mainwindow.o       mainwindow::on_pushbutton_2_clicked() in mainwindow.o   "std::allocator<char>::allocator()", referenced from:       mainwindow::on_pushbutton_clicked() in mainwindow.o       mainwindow::on_pushbutton_2_clicked() in mainwindow.o   "std::allocator<char>::~allocator()", referenced from:       mainwindow::on_pushbutton_clicked() in mainwindow.o       mainwindow::on_pushbutton_2_clicked() in mainwindow.o   "std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, std::allocator<char> const&)", referenced from:       mainwindow::on_pushbutton_clicked() in mainwindow.o       mainwindow::on_pushbutton_2_clicked() in mainwindow.o   "std::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string()", referenced from:       mainwindow::on_pushbutton_clicked() in mainwindow.o       mainwindow::on_pushbutton_2_clicked() in mainwindow.o ld: symbol(s) not found architecture x86_64  **clang: error: linker command failed exit code 1** (use -v see invocation) make: *** [controller.app/contents/macos/controller] error 1 14:49:33: **the process "/usr/bin/make" exited code 2**. error while building/deploying project controller (kit: desktop qt 5.3 clang 64bit) when executing step "make" 

and here's .pro file:

qt       += core gui greaterthan(qt_major_version, 4): qt += widgets  target = controller template = app   sources += main.cpp\            mainwindow.cpp \            ../colordetection/colordetector.cpp \            colordetectcontroller.cpp  headers  += mainwindow.h \             ../colordetection/colordetector.h \             colordetectcontroller.h  forms    += mainwindow.ui  config += c++11 qmake_macosx_deployment_target = 10.10   includepath += "/usr/local/opt/opencv/include" \  libs += -l"/usr/local/opt/opencv/lib" \         -lopencv_core \         -lopencv_highgui \         -lopencv_imgproc 

i met similar warnings before, solved adding these 2 lines .pro file:

config += c++11  qmake_macosx_deployment_target = 10.10 

however, time doesn't work. can explain me how solve ? lot.

it aren't warnings, errors. linker errors. in particular, line

"std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, std::allocator<char> const&)", referenced from: 

means couldn't link standard std::string, weird.

it couldn't find libraries x64 architecture. doesn't see in config switch compile architecture, hence assumiing default behavior, in turn means according library (at least std::string) should have been shipped compiler.

it led me question (though gcc), problem in libstdc++ being old, , didn't contained definitions c++11 standard.

then looked @ the page description std::basic_string, , found since c++11 in members used std::allocator, see inside braces of undefined reference string.

hence problem c++ library being old. need update compiler. interesting thing noticed post: saying wrong version of clang. told clang-5.0, looked @ version in kubuntu, , 3.4. wondered: did long not updated system? decided peek at clang site, , found latest version (which written being «in progress») 3.7.

the last thing need mention 2 undefined references @ beginning — need add path library contains functions cv::imread, , cv::imshow.