r279135 - in /trunk/libstdc++-v3: ChangeLog inc...

[redi@gcc.gnu.org]

Author: redi
Date: Mon Dec  9 17:35:24 2019
New Revision: 279135

URL: https://gcc.gnu.org/viewcvs?rev=279135&root=gcc&view=rev
Log:
libstdc++: Implement ranges::safe_range for C++20 (P1870R1)

This change replaces the __forwarding_range implementation detail with
the ranges::safe_range concept and adds the ranges::enable_safe_range
variable template for opt-in in to the concept.

It also adjusts the begin/end/rbegin/rend customization point objects to
match the new rules for accessing rvalue ranges only when safe to do so.

	* include/bits/range_access.h (ranges::enable_safe_range): Define.
	(ranges::begin, ranges::end, ranges::rbegin, ranges::rend): Constrain
	to only accept types satisfying safe_range and treat argument as an
	lvalue when calling a member of performing ADL.
	(ranges::__detail::__range_impl, ranges::__detail::__forwarding_range):
	Remove.
	(ranges::range): Adjust definition.
	(ranges::safe_range): Define.
	(ranges::iterator_t, ranges::range_difference_t): Reorder definitions
	to match the synopsis in the working draft.
	(ranges::disable_sized_range): Remove duplicate definition.
	* include/experimental/string_view (ranges::enable_safe_range): Add
	partial specialization for std::experimental::basic_string_view.
	* include/std/ranges (ranges::viewable_range, ranges::subrange)
	(ranges::empty_view, ranges::iota_view): Use safe_range. Specialize
	enable_safe_range.
	(ranges::safe_iterator_t, ranges::safe_subrange_t): Define.
	* include/std/span (ranges::enable_safe_range): Add partial
	specialization for std::span.
	* include/std/string_view (ranges::enable_safe_range): Likewise for
	std::basic_string_view.
	* testsuite/std/ranges/access/begin.cc: Adjust expected results.
	* testsuite/std/ranges/access/cbegin.cc: Likewise.
	* testsuite/std/ranges/access/cdata.cc: Likewise.
	* testsuite/std/ranges/access/cend.cc: Likewise.
	* testsuite/std/ranges/access/crbegin.cc: Likewise.
	* testsuite/std/ranges/access/crend.cc: Likewise.
	* testsuite/std/ranges/access/data.cc: Likewise.
	* testsuite/std/ranges/access/end.cc: Likewise.
	* testsuite/std/ranges/access/rbegin.cc: Likewise.
	* testsuite/std/ranges/access/rend.cc: Likewise.
	* testsuite/std/ranges/empty_view.cc: Test ranges::begin and
	ranges::end instead of unqualified calls to begin and end.
	* testsuite/std/ranges/safe_range.cc: New test.
	* testsuite/std/ranges/safe_range_types.cc: New test.
	* testsuite/util/testsuite_iterators.h: Add comment about safe_range.

Added:
    trunk/libstdc++-v3/testsuite/std/ranges/safe_range.cc
      - copied, changed from r279111, trunk/libstdc++-v3/testsuite/std/ranges/empty_view.cc
    trunk/libstdc++-v3/testsuite/std/ranges/safe_range_types.cc
Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/bits/range_access.h
    trunk/libstdc++-v3/include/experimental/string_view
    trunk/libstdc++-v3/include/std/ranges
    trunk/libstdc++-v3/include/std/span
    trunk/libstdc++-v3/include/std/string_view
    trunk/libstdc++-v3/testsuite/std/ranges/access/begin.cc
    trunk/libstdc++-v3/testsuite/std/ranges/access/cbegin.cc
    trunk/libstdc++-v3/testsuite/std/ranges/access/cdata.cc
    trunk/libstdc++-v3/testsuite/std/ranges/access/cend.cc
    trunk/libstdc++-v3/testsuite/std/ranges/access/crbegin.cc
    trunk/libstdc++-v3/testsuite/std/ranges/access/crend.cc
    trunk/libstdc++-v3/testsuite/std/ranges/access/data.cc
    trunk/libstdc++-v3/testsuite/std/ranges/access/end.cc
    trunk/libstdc++-v3/testsuite/std/ranges/access/rbegin.cc
    trunk/libstdc++-v3/testsuite/std/ranges/access/rend.cc
    trunk/libstdc++-v3/testsuite/std/ranges/empty_view.cc
    trunk/libstdc++-v3/testsuite/util/testsuite_iterators.h