Similar to the this question. Needed throw a exception with a message using printf-like style instead of string cocatenation or iostreams. Using the C++ 20 Formatting Library:
throw std::runtime_error {
std::format("Critical error! Code {}: {}", errno, strerror(errno))
};
But it not feels ergonomic calling format in all exceptions with formatting, can it get better?
Yes it can!
#include <format>
#include <stdexcept>
class runtime_exc : public std::runtime_error
{
public:
template <class... Args>
runtime_exc(std::format_string<Args...> what_arg_fmt, Args&&... args)
: runtime_error { std::format(what_arg_fmt, args...) }
{
}
};
Usage:
throw runtime_exc { "Critical error!" };
throw runtime_exc {
"Critical error! Code {}: {}", errno, strerror(errno)
};
If you assemble the message with format in runtime you can use std::vformat. If needed locale you can add another constructor with it as first parameter. Note that std::format can throw.
EDIT: Barry comment, no need to move the format string and forward the arguments.