From c0e865f73ddee2e7247a23a7d57ad80261861d35 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Wed, 19 Feb 2025 14:46:32 +0000
Subject: [PATCH] libstdc++: Workaround Clang bug with __array_rank built-in
 [PR118559]

We started using the __array_rank built-in with r15-1252-g6f0dfa6f1acdf7
but that built-in is buggy in versions of Clang up to and including 19.

libstdc++-v3/ChangeLog:

	PR libstdc++/118559
	* include/std/type_traits (rank, rank_v): Do not use
	__array_rank for Clang 19 and older.
---
 libstdc++-v3/include/std/type_traits | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 33892818257..676cdf2d7e6 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -1484,7 +1484,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     };
 
   /// rank
-#if _GLIBCXX_USE_BUILTIN_TRAIT(__array_rank)
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__array_rank) \
+  && (!defined(__clang__) || __clang_major__ >= 20) // PR118559
   template<typename _Tp>
     struct rank
     : public integral_constant<std::size_t, __array_rank(_Tp)> { };
@@ -3656,7 +3657,8 @@ template <typename _Tp>
 template <typename _Tp>
   inline constexpr size_t alignment_of_v = alignment_of<_Tp>::value;
 
-#if _GLIBCXX_USE_BUILTIN_TRAIT(__array_rank)
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__array_rank) \
+  && (!defined(__clang__) || __clang_major__ >= 20) // PR118559
 template <typename _Tp>
   inline constexpr size_t rank_v = __array_rank(_Tp);
 #else