title: Qt Creator 3.2.2 / Mac OSX 10.9.3 Undefined symbol in Qt Creator, OK in command line
body: <p>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.</p>
  
  <p>costesmanager_gui.pro</p>
  
  <pre><code>#-------------------------------------------------
  #
  # 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
  </code></pre>
  
  <p>Output of command tree :</p>
  
  <pre><code>$ 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
  ...
  </code></pre>
  
  <p>Compiler output :</p>
  
  <pre><code>Undefined symbols for architecture x86_64:
    "YAML::LoadFile(std::string const&amp;)", 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"
  </code></pre>
  
  <p>My main.cpp file consists of a basic YAML::LoadFile("foo.bar") and trying to display it.</p>
  
  <p>I have tried to create a test.cpp calling <code>YAML::LoadFile()</code>, then compile it with the two following commands (Qt produces the same + all its including stuff, I can paste it as well) :</p>
  
  <pre><code>$ 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
  </code></pre>
  
  <p>... and it works.</p>
  
  <p>I don't know what I am missing.
  Thank you a lot !</p>
  
  <p>EDIT : if you have any suggestions to clean this tree, I would be thrilled. Don't know the standard way to organise all this.</p>