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* [gcc r11-10133] libstdc++: Make ranges::size and ranges::empty check for unbounded arrays
@ 2022-07-07 23:33 Jonathan Wakely
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From: Jonathan Wakely @ 2022-07-07 23:33 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:c8f091982c748a8a180e9e2b24740f9a388f63da
commit r11-10133-gc8f091982c748a8a180e9e2b24740f9a388f63da
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Sun Dec 12 21:16:25 2021 +0000
libstdc++: Make ranges::size and ranges::empty check for unbounded arrays
Passing IncompleteType(&)[] to ranges::begin produces an error outside
the immediate context, which is fine for ranges::begin, but it means
that we fail to enforce the SFINAE-able constraints for ranges::size and
ranges::size. They should not be callable for any array of unknown
bound, whether the type is complete or not. Because we don't enforce
that in their constraints, we get a hard error when they try to use
ranges::begin.
This simply adds explicit checks for arrays of unknown bound to the
constraints for ranges::size and ranges::empty. We only need to check it
for the __sentinel_size and __eq_iter_empty concepts, because those are
the ones that are relevant to arrays, and which try to use
ranges::begin.
libstdc++-v3/ChangeLog:
* include/bits/ranges_base.h (ranges::size, ranges::empty): Add
explicit check for unbounded arrays before using ranges::begin.
* testsuite/std/ranges/access/empty.cc: Check handling of unbounded
arrays.
* testsuite/std/ranges/access/size.cc: Likewise.
(cherry picked from commit 55823c5a0ba50022d7fcc95e74ec293143810ef6)
Diff:
---
libstdc++-v3/include/bits/ranges_base.h | 4 ++++
libstdc++-v3/testsuite/std/ranges/access/empty.cc | 10 ++++++++++
libstdc++-v3/testsuite/std/ranges/access/size.cc | 10 ++++++++++
3 files changed, 24 insertions(+)
diff --git a/libstdc++-v3/include/bits/ranges_base.h b/libstdc++-v3/include/bits/ranges_base.h
index 6d2d5bf939d..2a525e421b9 100644
--- a/libstdc++-v3/include/bits/ranges_base.h
+++ b/libstdc++-v3/include/bits/ranges_base.h
@@ -379,6 +379,8 @@ namespace ranges
template<typename _Tp>
concept __sentinel_size = requires(_Tp& __t)
{
+ requires (!is_unbounded_array_v<remove_reference_t<_Tp>>);
+
{ _Begin{}(__t) } -> forward_iterator;
{ _End{}(__t) } -> sized_sentinel_for<decltype(_Begin{}(__t))>;
@@ -462,6 +464,8 @@ namespace ranges
template<typename _Tp>
concept __eq_iter_empty = requires(_Tp& __t)
{
+ requires (!is_unbounded_array_v<remove_reference_t<_Tp>>);
+
{ _Begin{}(__t) } -> forward_iterator;
bool(_Begin{}(__t) == _End{}(__t));
diff --git a/libstdc++-v3/testsuite/std/ranges/access/empty.cc b/libstdc++-v3/testsuite/std/ranges/access/empty.cc
index b2d8b105325..693355c6cf5 100644
--- a/libstdc++-v3/testsuite/std/ranges/access/empty.cc
+++ b/libstdc++-v3/testsuite/std/ranges/access/empty.cc
@@ -119,6 +119,16 @@ test04()
static_assert( ! noexcept(std::ranges::empty(E3{})) );
}
+template<typename T>
+ concept has_empty = requires (T& t) { std::ranges::empty(t); };
+
+// If T is an array of unknown bound, ranges::empty(E) is ill-formed.
+static_assert( ! has_empty<int[]> );
+static_assert( ! has_empty<int(&)[]> );
+static_assert( ! has_empty<int[][2]> );
+struct Incomplete;
+static_assert( ! has_empty<Incomplete[]> );
+
int
main()
{
diff --git a/libstdc++-v3/testsuite/std/ranges/access/size.cc b/libstdc++-v3/testsuite/std/ranges/access/size.cc
index f25a1cb9ddb..db843cddccb 100644
--- a/libstdc++-v3/testsuite/std/ranges/access/size.cc
+++ b/libstdc++-v3/testsuite/std/ranges/access/size.cc
@@ -120,6 +120,16 @@ test06()
static_assert( std::ranges::size(R{}) == 42 );
}
+template<typename T>
+ concept has_size = requires (T& t) { std::ranges::size(t); };
+
+// If T is an array of unknown bound, ranges::size(E) is ill-formed.
+static_assert( ! has_size<int[]> );
+static_assert( ! has_size<int(&)[]> );
+static_assert( ! has_size<int[][2]> );
+struct Incomplete;
+static_assert( ! has_size<Incomplete[]> );
+
int
main()
{
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