Qt5.1/Qt5.2 + Mac OS 10.9 (Mavericks) + XCode 5.0.2, Undefined symbols for architecture x86_64

Question

Environment : Mac OS 10.9 + Qt5.1/Qt5.2 + OpenCV2.4.7 + XCode(5.0.2)

I can compile the following program via terminal

g++ -L/usr/local/lib -lopencv_core -lopencv_highgui \
    -I/usr/local/include  main.cpp

The program a.out runs normally.

However, when using Qt 5.1/5.2 to run this OpenCV program, I got "Undefined symbols for architecture x86_64".

However, Qt5 works normally for a simple HelloWorld c++ program.

What is going on ?

Here is the code.

#include <iostream>
#include "opencv2/highgui/highgui.hpp"

using namespace std ;
using namespace cv ;

int main()
{
    Mat img ;

    img = imread("image.jpg") ;

    return 0;
}

And this is the project setting

INCLUDEPATH += /usr/local/include

LIBS += -L/usr/local/lib

LIBS += -lopencv_core -lopencv_highgui -v

cache()

TEMPLATE = app
CONFIG += console
CONFIG -= app_bundle
CONFIG -= qt

SOURCES += main.cpp

Here is the compile message

/Users/XXX/Qt5.2.0/5.2.0-beta1/clang_64/bin/qmake -spec macx-clang CONFIG+=debug -o Makefile /Users/XXX/Desktop/untitled/untitled.pro

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -headerpad_max_install_names -Wl,-syslibroot

/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk -mmacosx-version-min=10.6 -o untitled main.o   -L/usr/local/lib -lopencv_core -lopencv_highgui -v 

with -v to show invocation

Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)
Target: x86_64-apple-darwin13.0.0
Thread model: posix

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld" -demangle -dynamic -arch x86_64 -headerpad_max_install_names -macosx_version_min 10.6.0 -o untitled -lcrt1.10.6.o -L/usr/local/lib -syslibroot

/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk main.o -lopencv_core -lopencv_highgui -lstdc++ -lSystem

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/5.0/lib/darwin/libclang_rt.osx.a

And here is the error message

Undefined symbols for architecture x86_64:
"cv::imread(std::string const&, int)", referenced from:
      _main in main.o
.... and so on

I checked the problem has nothing to do with -lstdc++ or -std=c++11 or -stdlib=libstdc++. by using command line compile.

Any ideas or suggestion?

Answer 1

This issue is answered in this post

http://qt-project.org/forums/viewthread/35646/

and explained by sandy.martel

I quoted here

Qt binary distribution compile with -stdlib=libstdc++ to be compatible with 10.6, Xcode 5 on 10.9 will select -stdlib=libc++ by default (for OS X 10.7 and better only). So symbol using classes from the standard library (like std::string in this case) will not resolve correctly at link time. This is why you’re seeing this error (Undefined symbols for architecture x86_64) . Look with which standard library opencv is built: otool -L libopencv_XXX.dylib. You’ll have to rebuild it with the right one or change Qt’s mkspec to use the newer one.

I solve this by changing ../Qt5.2.0/5.2.0-rc1/clang_64/mkspecs/macx-clang/qmake.conf

from

QMAKE_MACOSX_DEPLOYMENT_TARGET = 10.6

to

QMAKE_MACOSX_DEPLOYMENT_TARGET = 10.9

And remember clean your project before rebuild.