Undefined behaviour isn't a set of checks the compiler goes through before deciding to call invoke_nasal_demons() which you can then just replace with yell_loud

Undefined behaviour isn't a set of checks the compiler goes through before deciding to call invoke_nasal_demons() which you can then just replace with yell_loudly_about_UB(). Undefined behaviour is a set of conditions that the standard says they can pretend do not occur, ever, so certain results are easier to obtain because the UB is never checked for and assumed to have not occurred. UB is fundamentally not a well defined condition because it is the absence of knowledge about the state of a program, and many UB conditions are very very hard to detect if not actually impossible (cf Turing) which is why the standard says the compiler doesn't have to care to begin with. Its very nature means detecting UB in anything approaching a reliable way is impossible, the C standard is not remotely compatable with such an idea.