The bit declarations regularly fools people to think they work on single bits when extrapolating and using the same thing within expressions.

If Kiel can't accept 'const' on every location an ISO-compilant C compiler should, then the Keil compiler is most definitely in error.

And any compiler who adds own keywords without leading underscores are in violation, by playing in the namespace owned by the standard. Many compilers - for example gcc - did add own keywords in old releases, but later added a compiler switch to specify if the extensions should be allowed or not. Together with the switch, they then added a second set of keywords on the appropriate form.

With the keyword "__code", a developer could always take the decision to do #define code __code, or better #define CODE __code. But with the keyword "code", life would be very interesting if a future C standard would introduce the "code" keyword.

All better language standards has dedicated mechanisms for allowing compiler extensions.