[libcxx-commits] [libcxx] c40a686 - [libc++] Strip cv-refs in __desugars_to specialization for integral types (#208950)

[via libcxx-commits]

Author: Michael G. Kazakov
Date: 2026-07-21T07:40:22-04:00
New Revision: c40a68644c550dcfa3c3d0b560e3aeea1d159d79

URL: https://github.com/llvm/llvm-project/commit/c40a68644c550dcfa3c3d0b560e3aeea1d159d79
DIFF: https://github.com/llvm/llvm-project/commit/c40a68644c550dcfa3c3d0b560e3aeea1d159d79.diff

LOG: [libc++] Strip cv-refs in __desugars_to specialization for integral types (#208950)

This PR passes the argument type through `__remove_cvref_t` before
passing to `is_integral`.

Fixes #208236

Added: 
    

Modified: 
    libcxx/include/__algorithm/comp.h
    libcxx/test/libcxx/type_traits/desugars_to.compile.pass.cpp

Removed: 
    


################################################################################
diff  --git a/libcxx/include/__algorithm/comp.h b/libcxx/include/__algorithm/comp.h
index 38e2fb9f5e744..a83b6a8938998 100644
--- a/libcxx/include/__algorithm/comp.h
+++ b/libcxx/include/__algorithm/comp.h
@@ -13,6 +13,7 @@
 #include <__type_traits/desugars_to.h>
 #include <__type_traits/is_generic_transparent_comparator.h>
 #include <__type_traits/is_integral.h>
+#include <__type_traits/remove_cvref.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -47,7 +48,8 @@ template <class _Tp>
 inline const bool __desugars_to_v<__less_tag, __less<>, _Tp, _Tp> = true;
 
 template <class _Tp>
-inline const bool __desugars_to_v<__totally_ordered_less_tag, __less<>, _Tp, _Tp> = is_integral<_Tp>::value;
+inline const bool __desugars_to_v<__totally_ordered_less_tag, __less<>, _Tp, _Tp> =
+    is_integral<__remove_cvref_t<_Tp> >::value;
 
 template <>
 inline const bool __is_generic_transparent_comparator_v<__less<> > = true;

diff  --git a/libcxx/test/libcxx/type_traits/desugars_to.compile.pass.cpp b/libcxx/test/libcxx/type_traits/desugars_to.compile.pass.cpp
index 9134ac027d1ed..e28dbd8fa9ff2 100644
--- a/libcxx/test/libcxx/type_traits/desugars_to.compile.pass.cpp
+++ b/libcxx/test/libcxx/type_traits/desugars_to.compile.pass.cpp
@@ -10,6 +10,7 @@
 // UNSUPPORTED: gcc && c++11
 
 #include <__type_traits/desugars_to.h>
+#include <__algorithm/comp.h>
 
 struct Tag {};
 struct Operation {};
@@ -37,4 +38,22 @@ void tests() {
     static_assert(std::__desugars_to_v<Tag, Operation&&>, "");
     static_assert(std::__desugars_to_v<Tag, Operation const&&>, "");
   }
+
+  // Make sure that __less<> desugars to __totally_ordered_less_tag for integral types regardless of their cv-ref
+  {
+    static_assert(std::__desugars_to_v<std::__totally_ordered_less_tag, std::__less<>, int, int>, "");
+    static_assert(std::__desugars_to_v<std::__totally_ordered_less_tag, std::__less<>, int&, int&>, "");
+    static_assert(std::__desugars_to_v<std::__totally_ordered_less_tag, std::__less<>, const int, const int>, "");
+    static_assert(std::__desugars_to_v<std::__totally_ordered_less_tag, std::__less<>, const int&, const int&>, "");
+    static_assert(
+        std::__desugars_to_v<std::__totally_ordered_less_tag, std::__less<>, volatile int&, volatile int&>, "");
+    static_assert(
+        std::__desugars_to_v<std::__totally_ordered_less_tag, std::__less<>, volatile const int&, volatile const int&>,
+        "");
+    static_assert(!std::__desugars_to_v<std::__totally_ordered_less_tag,
+                                        std::__less<>,
+                                        volatile const float&,
+                                        volatile const float&>,
+                  "");
+  }
 }