Re: Location of symbol definition

dfx schrieb:
> Hi,
> often in code written by 'gurus' I find expressions of the type
>   # if defined (__AVR_ATmega168__), but looking at the code I can not 
> find the definition anywhere.
> 
> The question is: where these symbols (with double underscore) are defined?

These are built-in defines, some of the AVR-specific ones are explained at

http://gcc.gnu.org/onlinedocs/gcc/AVR-Options.html

In order to find the location of a definition, add -g3 -save-temps to 
the compiler command options and inspect the respective .i (for C) or 
.ii (for C++) files.  It lists how a macro is defined and where a 
definition comes from, e.g. command line, built-in or some source #define.

Johann