Calls to printf() are particularly common in signal handlers I've seen in commercial code. malloc() too occasionally. Sometimes calls to logging functions Thes

Calls to printf() are particularly common in signal handlers I've seen in commercial code. malloc() too occasionally. Sometimes calls to logging functions These are undefined behaviour, for real (and for good reasons), not just theoretically. They are a cause of reported occasional random crashes, but people don't realise, and it's tricky to demonstrate or warn at compile time.