This assumption is allowed, as n=0 results in infinite recursion (without side-effects) which is undefined behavior: https://en.cppreference.com/w/cpp/language

This assumption is allowed, as n=0 results in infinite recursion (without side-effects) which is undefined behavior: https://en.cppreference.com/w/cpp/language/memory_model https://en.cppreference.com/w/cpp/language/memory_model https://en.cppreference.com/w/cpp/language/ub#Infinite_loop_without_side-effects https://en.cppreference.com/w/cpp/language/ub#Infinite_loop_...