- add compiler hint for checking the arguments of printf.
- change the return value of printf. from std::expected to normal value. use C++ exception to indicate error.
* the error of printf usually caused by programmer. so it can be found when testing program.
* so i use std::logic_error to indicate this and programmer should fix this before releasing program.
- change the use of encoding convertion. for those cases that convertion must be safe, we unwrap it directly.
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