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mcci-catena / Catena-Arduino-Platform

Arduino platform library for MCCI Catena IoT Systems
MIT License
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Refactor STM32 classes to be more like Samd21 #103

Closed terrillmoore closed 5 years ago

terrillmoore commented 5 years ago

Samd21 classes use an elaborate technique to avoid conditional compiles, based on the C compiler's ability to optimize out globals that aren't used.

  1. The table of platforms contains all the known platforms.
  2. The actual class Catena4450, etc., has a getPlatformTable() method that returns the platforms supported by the device.
  3. Startup code calls that as needed.
  4. Other platforms in the vector aren't referenced, so they're discarded.

STM32 classes instead have a table that's constructed with #if. This is much more fragile.

Please refactor the Stm32 classes to use the Samd21 technique.

chwon64 commented 5 years ago

Do you also want to remove #if when declare table instances as below?

https://github.com/mcci-catena/Catena-Arduino-Platform/blob/4ccdeff9d6481a8cbb6efd9eabc3cf814b8d7c50/src/lib/stm32/CatenaStm32_gk_PlatformHierarchy.cpp#L71-L87

If we remove this #if, these table instances are constructed and actual code size will be increased.

terrillmoore commented 5 years ago

The linker is supposed to remove the unused CATENA_PLATFORM instances, because there will be no reference to them (this is the --gc-sections option). You can compare size after you take out the #ifs; size shouldn't change. That's why I used this sort of strange format rather than a vector.

chwon64 commented 5 years ago

I checked the linker doesn't remove the unused CATENA_PLATORM instances. I also checked --gc-sections option applied when build STM32.

chwon64 commented 5 years ago

All changes are merged.