setting CoreDebug->DEMCR

[reimerp]

Hi, first thank you for the enlightening book and resources.
While implemeting I found a little type in the examples given on pages 79 and 118:
CoreDebug->DEMCR = CoreDebug_DEMCR_TRCENA_Msk;
should be replaced with
CoreDebug->DEMCR =| CoreDebug_DEMCR_TRCENA_Msk;

else tracing will fail if running in debugger which already sets DEMCR to != 0

[reimerp]

There is another one in int semihosting() (in the examples)
if this function is declared "naked", the compiler omits the epilogue. Its working in debug only, since the function does not return when free running.
just add

#if defined __ARM_ARCH && __ARM_ARCH == 7
  }
  __asm__ ("bx   lr \n");
#endif