Usually I compile all my projects with the -Wall option of g++, as the warnings are often quite use full. Unfortunately Box2D itself produces so many warnings, that compiling with this option it is almost useless for debugging my own code.
Most of the warnings are of the form
./src/Box2D/Include/../Source/Dynamics/b2WorldCallbacks.h: In member function ‘virtual void b2ContactListener::Add(const b2ContactPoint*)’:
./src/Box2D/Include/../Source/Dynamics/b2WorldCallbacks.h:95: warning: statement has no effect
so it should be easy to fix them.
Would help a lot when working with Box2D!