title: qmake platform scopes
body: <p>A standard c++ qmake-based library is developed for Win32, Mac, and Linux. In the qmake project file, the platform-dependent sources are included like this:</p>
  
  <pre><code>win32 {
       SOURCES += WinSystem.cpp
       HEADERS += WinSystem.h
   }
  
  macx {
       SOURCES += MacSystem.cpp
       HEADERS += MacSystem.h
  }
  
  unix {
       SOURCES += LinuxSystem.cpp
       HEADERS += LinuxSystem.h
  }
  </code></pre>
  
  <p>Now on OS X both <code>unix</code> and <code>macx</code> are defined, so the Linux files are also included and cause error! What is the solution to this?</p>