[Bug libstdc++/116529] Construction of unique_ptr with reference type is rejected because of auto_ptr constructor

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116529

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-08-29
           Keywords|                            |rejects-valid
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
And this fixes it:

diff --git a/libstdc++-v3/include/backward/auto_ptr.h
b/libstdc++-v3/include/backward/auto_ptr.h
index 271a64d1de0..9e1318a9d9d 100644
--- a/libstdc++-v3/include/backward/auto_ptr.h
+++ b/libstdc++-v3/include/backward/auto_ptr.h
@@ -329,7 +329,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 #endif // HOSTED

   template<typename _Tp, typename _Dp>
-  template<typename _Up, typename>
+  template<typename _Up, typename, typename>
     inline
     unique_ptr<_Tp, _Dp>::unique_ptr(auto_ptr<_Up>&& __u) noexcept
     : _M_t(__u.release(), deleter_type()) { }
diff --git a/libstdc++-v3/include/bits/unique_ptr.h
b/libstdc++-v3/include/bits/unique_ptr.h
index 0f600db32f9..167136fe890 100644
--- a/libstdc++-v3/include/bits/unique_ptr.h
+++ b/libstdc++-v3/include/bits/unique_ptr.h
@@ -379,8 +379,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
       /// Converting constructor from @c auto_ptr
-      template<typename _Up, typename = _Require<
-              is_convertible<_Up*, _Tp*>, is_same<_Dp, default_delete<_Tp>>>>
+      template<typename _Up, typename _Tpp = typename add_pointer<_Tp>::type,
+              typename = _Require<is_convertible<_Up*, _Tpp>,
+                                  is_same<_Dp, default_delete<_Tp>>>>
        unique_ptr(auto_ptr<_Up>&& __u) noexcept;
 #pragma GCC diagnostic pop
 #endif