Boost C++ Libraries: Ticket #9211: fstream types don't have move semantics

type changed

viboes — Tue, 08 Oct 2013 17:24:08 GMT

type Bugs → Feature Requests

How is this a bug?

anonymous — Wed, 09 Oct 2013 07:55:09 GMT

Replying to viboes:

How is this a bug?

I understand the filesystem::fstream classes as drop-in replacements for the std ones to support filesystem::path. When a feature that prevents intended operation is missing, I think of it as a bug rather than a feature request, but it's probably a matter of definition.

anonymous — Mon, 24 Mar 2014 09:36:46 GMT

Here is a use case:

template <typename Stream, typename... Args>
Stream StreamOpen(Args&&... args) {
	Stream stream;
	stream.exceptions(ios::failbit | ios::badbit);
	stream.open(forward<Args>(args)...);
	return stream;
}

auto f1 = StreamOpen<std::ifstream>("filename", std::ios::binary); // succeeds
auto f2 = StreamOpen<boost::filesystem::ifstream>("filename", std::ios::binary); // fails

cc set

mail@… — Sun, 04 May 2014 11:33:23 GMT

cc mail@… added

summary changed

anonymous — Tue, 27 May 2014 11:37:01 GMT

summary fstream types don't have move semantics → fstream types don't have move semantics or swap method

boost::filesystem::*fstream are missing the swap methods from std::*fstream as well. Since the boost classes don't have any data, would just adding stubs that call the std ones be enough?

summary changed

anonymous — Tue, 27 May 2014 12:07:03 GMT

summary fstream types don't have move semantics or swap method → fstream types don't have move semantics

Actually the boost classes don't need swap methods of their own, they can just use the ones inherited from std:

class myifstream : public boost::filesystem::ifstream {
	myifstream() { }
	myifstream(myifstream&& other) {
		swap(other);
	}
	myifstream& operator=(myifstream&& other) {
		swap(other);
		return *this;
	}
};

auto f3 = StreamOpen<myifstream>("filename", std::ios::binary); // succeeds