Arduino platform compiler flag

Question

Is there's any compiler flag to indicate the platform? eg:

#ifdef ARDUINO_UNO
....//code for uno
#elif ARDUINO_NANO
...//code for nano
#else
error("unknown platform");
#endif

Answer 1

In Arduino.h file, you can find the following preprocessor checks:

#if defined(__AVR_ATtiny24__) || defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__) || defined(__AVR_ATtiny25__) || defined(__AVR_ATtiny45__) || defined(__AVR_ATtiny85__)
...
#else  
#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__) || defined(__AVR_ATmega1284__) || defined(__AVR_ATmega1284P__) || defined(__AVR_ATmega644__) || defined(__AVR_ATmega644A__) || defined(__AVR_ATmega644P__) || defined(__AVR_ATmega644PA__)
...
#endif

I never tried these, but do not I see why you will not be able to use them in your code as well.