[BUG] true/false always redefined if stdbool.h and Arduino.h are both included when using C.

[xxxajk]

Arduino.h always defines true and false, the trouble occurs when you use C, and include stdbool.h. Arduino.h should simply include stdbool.h instead of defining these for C code, and only define them if using C++.

Details: this seems to happen only for C code, not C++ or a sketch. I have situations where I write a library with mixed C and C++. This causes GCC to emit redefinition warnings.

[matthijskooijman]

Arduino.h always defines true and false, the trouble occurs when you use C, and include stdbool.h. Arduino.h should simply include stdbool.h instead of defining these for C code, and only define them if using C++.
You say to only define them if using C++, but AFAIU they are language keyword in C++, so there is no need to define them (if you do, you'll be using integers instead of the actual true and false keywords, which will also work, but is not so nice).

So I think that we should just replace the true and false definitions with an #include <stdbool.h> and be done with it. For C, that will make true, false and bool available, for C++ that will just use the C++ keywords (stdbool.h contains a check for C vs C++).

[cmaglie]

Fixed with #1877.