How about circumstances such as opting in to a semantically new version of C? #ifndef __CC_VOLATILE_FUNCTIONS /\* No volatile function support, remove code

How about circumstances such as opting in to a semantically new version of C? #ifndef __CC_VOLATILE_FUNCTIONS /\* No volatile function support, remove code */ #define VOLFUNC #else /* This compiler supports volatile functions. Only volatile functions may cause external side effects without likely bugs. */ #define VOLFUNC volatile #endif https://www.postgresql.org/docs/current/xfunc-volatility.html https://www.postgresql.org/docs/current/xfunc-volatility.htm... Similarly stable functions could have results cached. You might also note that PostgreSQL assumes any undeclared function is volatile.