Lots of warnings are produced when compiling for F407
e.g.
MakerLabMe\MakerLabMe\variants\F4Discovery/libstm_stm32f40x_8Mhz_gcc_rel.a(startup_stm32f4xx.o):(.isr_vector+0x108): warning: undefined reference to TIM5_IRQHandler' \variant.cpp.o: In functionUART4_IRQHandler':
\MakerLabMe\variants\F4Discovery/variant.cpp:314: warning: undefined reference to Serial1' \variant.cpp.o: In functionUSART2_IRQHandler':
MakerLabMe\variants\F4Discovery/variant.cpp:319: warning: undefined reference to `Serial2'
These errors are compiling an empty sketch in IDE 1.6.3