FSL has many MCU to support. I found many conditional compilation in source code, such as USB stack and bootloaders.
Conditional compilation macros are useful in simple build time customization.
However it becomes more and more confusion as more and more custom code are added, because of MCU families, peripherals, application customization, compilers. The developers will find these conditions are mess up and hard to read.
I would like to suggest FSL team to use seperate folder to replace conditional compilation macros.