`ec` is an error code. What happens is a conversion to bool, see `operátor bool()` https://en.cppreference.com/w/cpp/utility/to_chars_result https://en.cpprefer

`ec` is an error code. What happens is a conversion to bool, see `operátor bool()` https://en.cppreference.com/w/cpp/utility/to_chars_result https://en.cppreference.com/w/cpp/utility/to_chars_result And no, don't ask mé why somebody might think that a bool is a suitable type to check for success or error.