How about putting #if !defined(__AVR__) && !defined(__MSP430__) #warning "Fix this FIFO - ++/-- possibly not atomic!" #endif into the header of that thingy

How about putting #if !defined(__AVR__) && !defined(__MSP430__) #warning "Fix this FIFO - ++/-- possibly not atomic!" #endif into the header of that thingy then. Save work on small uCs, and be warned when moving it somewhere else.