title: Makefile dependency generation not checking headers
body: <p>I'm using a makefile intending to generate dependencies automatically. But with my file, I find that although changes to the header files cause the code to be recompiled, they don't cause the dependencies to be regenerated, as I think they ought. Can anyone see what I have missed out?</p>
  
  <pre><code>.SUFFIXES : .hpp .cpp .d .o
  SOURCES=main.cpp sub1.cpp sub2.cpp
  OBJECTS=${SOURCES:.cpp=.o}
  DEPENDENCIES=${SOURCES:.cpp=.d}
  
  .cpp.d:
      g++ -MM $&lt; &gt; $@
  .cpp.o:
      g++ $&lt; -c `pkg-config gtkmm-2.4 --cflags --libs` -g
  
  calculator: ${OBJECTS} ${DEPENDENCIES}
      g++ ${OBJECTS} -o calculator `pkg-config gtkmm-2.4 --cflags --libs` -g
  
  include ${DEPENDENCIES}
  </code></pre>