inaccessible base class in PWTimer

In PWTimer the Register class is used as a base class twice. Getting a compiler warning, but maybe only in env:asm-listing.

The full compiler warning is:

include/timers.h:88:8: warning: direct base 'Register' inaccessible in 'PWMTimer<(TimerBlockIndex)1, (TimerIndex)1>' due to ambiguity [enabled by default]
 struct PWMTimer : Timer<timerBlockIndex, timerIndex>, Register {

Solution may be:


// #pragma warning(suppress: 4250) // inherits via dominance
#pragma GCC diagnostic ignored "-Winaccessible-base"
struct PWTimer

The intention of subclassing PWMTimer from Timer is to interpret the GPTMTBILR and GPTMTBPR as a single 24-bit value. Although Register is inherited in Timer, if it's left out of the PWMTimer declaration, the compiler then complains with error:

include/timers.h:92:5: error: 'RegisterSpan' does not name a type
     RegisterSpan<R.GPTMTBILR, 16, R.GPTMTBPR, 8> pwmInterval;

So there are two puzzles here:

why does Register need to be re-inherited in the derived class
why does the double inheritance throw a warning. IIRC there was some talk that the warning is just for puristes who want to have such potential double inheritance flagged. It is just warning. The other purists would rather have a way to suppress such warnings, like "I know what I'm doing here".

fweiss / tm4c-led-pwm

inaccessible base class in PWTimer #3