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libstdc++: Avoid accidental ADL when calling make_reverse_iterator

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std::ranges::reverse_view uses make_reverse_iterator in its
implementation as described in [range.reverse.view]. This accidentally
allows ADL as an unqualified name is used in the call. According to
[contents], however, this should be treated as a qualified lookup into
the std namespace.

This leads to errors due to ambiguous name lookups when another
make_reverse_iterator function is found via ADL.

libstdc++-v3/Changelog:

	* include/std/ranges (reverse_view::begin, reverse_view::end):
	Qualify make_reverse_iterator calls to avoid ADL.
	* testsuite/std/ranges/adaptors/reverse.cc: Test that
	views::reverse works when make_reverse_iterator is defined
	in an associated namespace.
This commit is contained in:
Moritz Sichert 2021-03-23 15:47:37 +00:00 committed by Jonathan Wakely
parent 6b1f841ce0
commit 09f08fef71
2 changed files with 24 additions and 6 deletions
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12
libstdc++-v3/include/std/ranges
View File

@ -2958,29 +2958,29 @@ namespace views
{
if constexpr (_S_needs_cached_begin)
if (_M_cached_begin._M_has_value())
return make_reverse_iterator(_M_cached_begin._M_get(_M_base));
return std::make_reverse_iterator(_M_cached_begin._M_get(_M_base));
auto __it = ranges::next(ranges::begin(_M_base), ranges::end(_M_base));
if constexpr (_S_needs_cached_begin)
_M_cached_begin._M_set(_M_base, __it);
return make_reverse_iterator(std::move(__it));
return std::make_reverse_iterator(std::move(__it));
}
constexpr auto
begin() requires common_range<_Vp>
{ return make_reverse_iterator(ranges::end(_M_base)); }
{ return std::make_reverse_iterator(ranges::end(_M_base)); }
constexpr auto
begin() const requires common_range<const _Vp>
{ return make_reverse_iterator(ranges::end(_M_base)); }
{ return std::make_reverse_iterator(ranges::end(_M_base)); }
constexpr reverse_iterator<iterator_t<_Vp>>
end()
{ return make_reverse_iterator(ranges::begin(_M_base)); }
{ return std::make_reverse_iterator(ranges::begin(_M_base)); }
constexpr auto
end() const requires common_range<const _Vp>
{ return make_reverse_iterator(ranges::begin(_M_base)); }
{ return std::make_reverse_iterator(ranges::begin(_M_base)); }
constexpr auto
size() requires sized_range<_Vp>

18
libstdc++-v3/testsuite/std/ranges/adaptors/reverse.cc
View File

@ -131,6 +131,23 @@ test05()
VERIFY( test_wrapper<int>::increment_count == 5 );
}
namespace test_ns
{
struct A {};
template <typename T>
void make_reverse_iterator(T&&) {}
} // namespace test_ns
void test06()
{
// Check that views::reverse works and does not use ADL which could lead
// to accidentally finding test_ns::make_reverse_iterator(const A&).
test_ns::A as[] = {{}, {}};
auto v = as | std::views::reverse;
static_assert(std::ranges::view<decltype(v)>);
static_assert(std::ranges::view<decltype(v)>);
}
int
main()
{
@ -139,4 +156,5 @@ main()
test03();
test04();
test05();
test06();
}