libstdc++: Fix helper concept for ranges::data [PR 100824]

We need to decay the result of t.data() before checking if it's a
pointer.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:

	PR libstdc++/100824
	* include/bits/ranges_base.h (__member_data): Use __decay_copy.
	* testsuite/std/ranges/access/data.cc: Add testcase from PR.

(cherry picked from commit 3e5f2425f80aedd00f28235022a2755eb46f310d)

diff --git a/libstdc++-v3/include/bits/ranges_base.h b/libstdc++-v3/include/bits/ranges_base.h
index 17a421a492799c1397fd14236dbafdbb458a694a..61d91eb8389a8f3e5da68990d0043b80fe973d3a 100644 (file)
--- a/libstdc++-v3/include/bits/ranges_base.h
+++ b/libstdc++-v3/include/bits/ranges_base.h
@@ -495,8 +495,10 @@ namespace ranges
                                    && is_object_v<remove_pointer_t<_Tp>>;
 
     template<typename _Tp>
-      concept __member_data
-       = requires(_Tp& __t) { { __t.data() } -> __pointer_to_object; };
+      concept __member_data = requires(_Tp& __t)
+       {
+         { __cust_access::__decay_copy(__t.data()) } -> __pointer_to_object;
+       };
 
     template<typename _Tp>
       concept __begin_data = requires(_Tp& __t)

diff --git a/libstdc++-v3/testsuite/std/ranges/access/data.cc b/libstdc++-v3/testsuite/std/ranges/access/data.cc
index 237bbcc76c57d5c2652d39c7bda0d4336254fd72..4f16f447f9fc24763f419305afa41c5412b3e2ec 100644 (file)
--- a/libstdc++-v3/testsuite/std/ranges/access/data.cc
+++ b/libstdc++-v3/testsuite/std/ranges/access/data.cc
@@ -92,8 +92,12 @@ test03()
   // ranges::data should treat the subexpression as an lvalue
   VERIFY( std::ranges::data(std::move(r)) == &R3::i );
   VERIFY( std::ranges::data(std::move(c)) == &R3::l );
-}
 
+  // PR libstdc++/100824 comment 3
+  // Check for member data() should use decay-copy
+  struct A { int*&& data(); };
+  static_assert( has_data<A&> );
+}
 
 int
 main()