[PATCH] Implement P0084R2, Emplace return type, for C++17

[Jonathan Wakely <jwakely at redhat dot com>]

In C++17 the emplace_front and emplace_back members return a
reference. There isn't a very neat way to implement this, so it's just
lots of conditional compilation.

This isn't an ABI break, because these member functions are templates
and so the return type is part of the mangled name. We can't apply it
retroactively to older standards though, because it breaks code that
is valid in C++14, such as:

 void f(std::vector<int>& v) { return v.emplace_back(1); }


	* doc/xml/manual/status_cxx2017.xml: Update status.
	* doc/html/*: Regenerate.
	* include/bits/deque.tcc (deque::emplace_front, deque::emplace_back):
	Return a reference in C++17 mode.
	* include/bits/forward_list.h (forward_list::emplace_front): Likewise.
	* include/bits/stl_bvector.h (vector<bool>::emplace_back): Likewise.
	* include/bits/stl_deque.h (deque::emplace_front, deque::emplace_back):
	Likewise.
	* include/bits/stl_list.h (list::emplace_front, list::emplace_back):
	Likewise.
	* include/bits/stl_queue.h (queue::emplace): Likewise.
	* include/bits/stl_stack.h (stack::emplace): Likewise.
	* include/bits/stl_vector.h (vector::emplace_back): Likewise.
	* include/bits/vector.tcc (vector::emplace_back): Likewise.
	* include/debug/deque (__gnu_debug::deque::emplace_front)
	(__gnu_debug::deque::emplace_back): Likewise.
	* include/debug/vector (__gnu_debug::vector::emplace_back): Likewise.
	* testsuite/23_containers/deque/modifiers/emplace/cxx17_return.cc:
	New.
	* testsuite/23_containers/forward_list/modifiers/
	emplace_cxx17_return.cc: New.
	* testsuite/23_containers/list/modifiers/emplace/cxx17_return.cc: New.
	* testsuite/23_containers/queue/members/emplace_cxx17_return.cc: New.
	* testsuite/23_containers/stack/members/emplace_cxx17_return.cc: New.
	* testsuite/23_containers/vector/bool/emplace_cxx17_return.cc: New.
	* testsuite/23_containers/vector/modifiers/emplace/cxx17_return.cc:
	New.

Tested powerpc64le-linux, committed to trunk.

Attachment: patch.txt
Description: Text document