I am developing libraries for compatibility across a number of Arduino/compatible boards. I know that Arduino boards can be identified by the test "#if defined (AVR_ATmega328P)" and compatibles as well, for example: #if defined(TM4C123GH6PM). There are a few lists of these IDs on the web but they are all outdated. I have searched various hardware\core folders and various library code and do not see where these #defines are actually defined.
Where and in what format are board signatures stored? Is there c++ code that can find the board signature? Does anyone know of a site where these signatures are stored and updated by the Arduino community?