GCC 9 throws function cast warnings about fastdelegate

[mikepurvis]

I see this building our firmwares using gcc-arm-none-eabi=15:9-2019-q4-0ubuntu1, the version currently in Ubuntu Focal:

/usr/arm-none-eabi/include/stm32plus-040006/event/fd/FastDelegate.h:318:22: error: cast between incompatible pointer to member types from 'void (adc_helpers::AdcDmaDriver<stm32plus::Dma2Channel2Stream0<stm32plus::AdcDmaFeature<stm32plus::PeripheralTraits<stm32plus::PERIPHERAL_ADC3>, true, 131072, 0>, stm32plus::DmaInterruptFeature<2, 0> >, 0>::*)(stm32plus::DmaEventType)' to 'void (fastdelegate::detail::GenericClass::*)()' [-Werror=cast-function-type]
cc1plus: all warnings being treated as errors

Looks like that file is vendored in from an upstream that no longer exists; I can't find any newer versions of it that have been patched for this, and I'm not sure what the proper fix would look like.

[mikepurvis]

Note that with cppcheck turned out there are also a ton of new warnings, especially about uninitialized members and absense of the override keyword.

[mikepurvis]

For now we're simply passing -Wno-cast-function-type in order to move forward with our migration. I attempted to cast through void* and the compiler was still getting hung up on this, so I'm not sure what the proper resolution would be.