Unsetting all the formatting flags

Question

Is it legal to unset all the formatting flags using unsetf in C++?

Or is it at least legal to unset all the basefield or floatfield flags?

What's the defined behavior of e.g. std::cout for that?

Answer 1

The behaviour is indeed defined. I looked this up when writing an insertion operator for big integers. Tables providing format specifiers for specific flags like table 75 (which concerns basefield) or table 76 (floatfield) have a default in any case. See also cppreference/num_put.