title: qt add path for 3rd party header and libraries
body: <p>I am using qt and developing a desktop app that will run under win xp/vista.</p>
  
  <p>I have a 3rd party library UserAgentLib (static, and shared). But I am not sure how to link in qt creator. </p>
  
  <p>I have opened the *.pro file and added my library and header path.
  The library is called UserAgentLib and the header file is called UserAgentLib.h</p>
  
  <pre><code>TARGET = Dialer
  TEMPLATE = app
  
  LIBS += D:\Projects\qtDialer\tools\lib\UserAgentLib
  INCLUDEPATH += D:\Projects\qtDialer\tools\inc
  
  SOURCES += main.cpp\
          catdialer.cpp
  
  HEADERS  += catdialer.h
  
  FORMS    += catdialer.ui
  </code></pre>
  
  <p>I think it does find the header file, as I get about 100 errors for declarations in the UserAgentLib.h file. However, I don't think it is linking with the library.</p>
  
  <p>Many thanks for any suggestions,</p>
  
  <p>======================</p>
  
  <p>I have create a very simple library in VS C++ 2008. Here is the code for the header and source file.
  Header:</p>
  
  <pre><code>// mathslibrary.hpp
  int add_numbers(const int a, const int b);
  </code></pre>
  
  <p>Source:</p>
  
  <pre><code>// mathslibrary.cpp
  #include "mathslibrary.hpp"
  int add_numbers(const int a, const int b)
  {
  return a + b;
  }
  </code></pre>
  
  <p>I have compiled this into a library. And tested by linking with a WIN32 console application in VS 2008. The library worked as expected.</p>
  
  <p>Now when I try and link with qt.</p>
  
  <pre><code>#include &lt;QtCore/QCoreApplication&gt;
  #include &lt;iostream&gt;
  #include "mathslibrary.hpp"
  int main(int argc, char *argv[])
  {
      QCoreApplication a(argc, argv);
      std::cout &lt;&lt; "add numbers 40 + 60 = " &lt;&lt; add_numbers(40, 60) &lt;&lt; std::endl;
      return a.exec();
  }
  </code></pre>
  
  <p>This is my qmake file:</p>
  
  <pre><code>QT       -= gui
  TARGET = testlibrary
  CONFIG   += console
  CONFIG   -= app_bundle
  TEMPLATE = app
  LIBS = D:\Projects\TestLibrary\mathsLibrary\Debug\mathsLibrary.lib
  INCLUDEPATH = D:\Projects\TestLibrary\mathsLibrary\
  SOURCES += main.cpp
  </code></pre>
  
  <p>These are the errors I get when I try and build:</p>
  
  <p>c:/Qt/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../libmingw32.a(main.o):main.c::-1: error: undefined reference to `WinMain@16'</p>
  
  <p>:-1: error: collect2: ld returned 1 exit status</p>
  
  <p>And these are the compile issues:</p>
  
  <p>Running build steps for project testlibrary...</p>
  
  <p>Creating gdb macros library...</p>
  
  <p>Configuration unchanged, skipping QMake step.</p>
  
  <p>Starting: C:/Qt/mingw/bin/mingw32-make.exe debug -w </p>
  
  <p>mingw32-make: Entering directory `D:/Projects/TestQTLibrary/testlibrary'</p>
  
  <p>C:/Qt/mingw/bin/mingw32-make -f Makefile.Debug
  mingw32-make[1]: Entering directory `D:/Projects/TestQTLibrary/testlibrary'</p>
  
  <p>g++ -enable-stdcall-fixup -Wl,-enable-auto-import -Wl,-enable-runtime-pseudo-reloc -Wl,-subsystem,console -mthreads -Wl -o debug\testlibrary.exe   -L"c:\Qt\qt\lib" </p>
  
  <p>D:\Projects\TestLibrary\mathsLibrary\Debug\mathsLibrary.lib -lQtCored4
  mingw32-make[1]: Leaving directory `D:/Projects/TestQTLibrary/testlibrary'</p>
  
  <p>mingw32-make: Leaving directory `D:/Projects/TestQTLibrary/testlibrary'</p>
  
  <p>c:/Qt/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../libmingw32.a(main.o):main.c:</p>
  
  <p>(.text+0x104): undefined reference to `WinMain@16'
  collect2: ld returned 1 exit status
  mingw32-make[1]: <strong>* [debug\testlibrary.exe] Error 1
  mingw32-make: *</strong> [debug] Error 2
  Exited with code 2.
  Error while building project testlibrary
  When executing build step 'Make'</p>
  
  <p>Many thanks for any advice,</p>