Qt Creator 3.2.2 / Mac OSX 10.9.3 Undefined symbol in Qt Creator, OK in command line

Question

I'm having this issue where the linker fails due to an undefined symbol while it works great in command line. Hope you guys can help me to figure this out.

costesmanager_gui.pro

#-------------------------------------------------
#
# Project created by QtCreator 2014-10-22T14:45:23
#
#-------------------------------------------------

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = costesmanager_gui
TEMPLATE = app

SOURCES += main.cpp\
        mainwindow.cpp

HEADERS  += mainwindow.h

FORMS    += mainwindow.ui

INCLUDEPATH += /Users/noe/boost_1_56_0

LIBS += -L/Users/noe/costesmanager/gui/costesmanager_gui/lib -lyaml-cpp

INCLUDEPATH += /Users/noe/costesmanager/gui/costesmanager_gui/yaml-cpp/include

Output of command tree :

$ tree
.
├── costesmanager_gui.pro
├── costesmanager_gui.pro.user
├── lib
│   └── libyaml-cpp.a
├── main.cpp
├── mainwindow.cpp
├── mainwindow.h
├── mainwindow.ui
├── test.cpp
└── yaml-cpp
 ...
    ├── include
    │   └── yaml-cpp
...
    │       └── yaml.h
...

Compiler output :

Undefined symbols for architecture x86_64:
  "YAML::LoadFile(std::string const&)", referenced from:
      _main in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [costesmanager_gui.app/Contents/MacOS/costesmanager_gui] Error 1
15:50:30: Le processus "/usr/bin/make" s'est terminé avec le code 2.
Erreur lors de la compilation/déploiement du projet costesmanager_gui (kit : Desktop Qt 5.3 clang 64bit)
When executing step "Make"

My main.cpp file consists of a basic YAML::LoadFile("foo.bar") and trying to display it.

I have tried to create a test.cpp calling YAML::LoadFile(), then compile it with the two following commands (Qt produces the same + all its including stuff, I can paste it as well) :

$ clang++ -c -I/Users/noe/costesmanager/gui/costesmanager_gui/yaml-cpp/include -I /Users/noe/boost_1_56_0 -o test.o test.cpp
$ clang++ test.o -o test -L/Users/noe/costesmanager/gui/costesmanager_gui/lib/ -lyaml-cpp

... and it works.

I don't know what I am missing. Thank you a lot !

EDIT : if you have any suggestions to clean this tree, I would be thrilled. Don't know the standard way to organise all this.

Answer 1

Okay so the solution was easy but really tricky to spot (crazy hunt).

Since there is two C++ standard libraries in OSX (see here), I had to specifically tell the compiler to use libc++.

Therefore I added

QMAKE_CXXFLAGS = -stdlib=libc++
LIBS += -stdlib=libc++

to my .pro file and everything works correctly now !

Still don't know why on command line I don't have to do this but... If someone has a clue ?

Have a good day everyone.