#include <iostream>
#include <array>
#include <algorithm>
#include <cstring>
 
using namespace std;
 
const unsigned int long_enough = 512;
class my_exception : public exception {
	std::array<char, long_enough> err;
	std::array<char, long_enough>::iterator insertion_point;
public:
	template <typename Iter>
	void append(Iter first, Iter last) noexcept {
		//Remember null terminator!
		auto space_left = std::distance(insertion_point, err.end());
		if (std::distance(first, last)>=space_left){
			last = first + (space_left - 1);
		}
		insertion_point = copy(first, last, insertion_point); //TODO: bounds, start
	}
	void append(const char msg[]) noexcept {
		append(msg, msg+strlen(msg));
	}
	my_exception(const char msg[]) noexcept {
		insertion_point = err.begin();
		append(msg, msg+strlen(msg));
	}
	virtual const char* what() const noexcept override{
		return err.data();
	}
};
 
void i_will_throw() {
	throw my_exception("i_will_throw: demonstrating exception propagation mechanism");
}
 
void i_will_rethrow() {
	try {
		i_will_throw();
	} catch (my_exception& e) {
		e.append("\n<<--via: i_will_rethrow");
		throw;
	}
}
 
void recurse_and_throw(char how_deep) {
	std::string name_with_depth = "\n<<--via: recurse_and_throw(";
	name_with_depth += how_deep; name_with_depth += ")";
	try {
		if (how_deep!='A') {
			recurse_and_throw(how_deep - 1);
		} else {
			i_will_throw();
			return;
		}
	} catch (my_exception& e) {
		e.append(name_with_depth.begin(), name_with_depth.end());
		throw;
	}
}
 
int main() {
	cout << "-------Simple--------" << endl;
	try {
		i_will_throw();
	} catch (exception& e) {
		cout << e.what()<<endl;
	}
	cout << "--------Rethrown-------" << endl;
	try {
		i_will_rethrow();
	} catch (exception& e) {
		cout << e.what()<<endl;
	}
	cout << "--------Recursive-------" << endl;
	try {
		recurse_and_throw('F');
	} catch (exception& e) {
		cout << e.what()<<endl;
	}
	cout << "--------Recursive long-------" << endl;
	try {
		recurse_and_throw('U');
	} catch (exception& e) {
		cout << e.what() <<endl;
	}
	return 0;
}

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