[libcxx-commits] [libcxx] [libc++] Simplify the implementation of the unique_ptr -> shared_ptr converting constructor (PR #165619)

[Nikolas Klauser via libcxx-commits]

https://github.com/philnik777 updated https://github.com/llvm/llvm-project/pull/165619

>From e7c3b6b966a1deaebff2f1965db4c50b0b0aa8be Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Wed, 29 Oct 2025 21:11:59 +0100
Subject: [PATCH] [libc++] Simplify the implementation of the unique_ptr ->
 shared_ptr converting constructor

---
 libcxx/include/__memory/shared_ptr.h          | 41 +++----------------
 .../unique_ptr.pass.cpp                       |  4 +-
 2 files changed, 8 insertions(+), 37 deletions(-)

diff --git a/libcxx/include/__memory/shared_ptr.h b/libcxx/include/__memory/shared_ptr.h
index e90db587d2836..7f639e37fcf08 100644
--- a/libcxx/include/__memory/shared_ptr.h
+++ b/libcxx/include/__memory/shared_ptr.h
@@ -487,45 +487,16 @@ class _LIBCPP_SHARED_PTR_TRIVIAL_ABI shared_ptr {
 
   template <class _Yp,
             class _Dp,
-            __enable_if_t<!is_lvalue_reference<_Dp>::value && __compatible_with<_Yp, _Tp>::value &&
+            __enable_if_t<__compatible_with<_Yp, _Tp>::value &&
                               is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, element_type*>::value,
                           int> = 0>
   _LIBCPP_HIDE_FROM_ABI shared_ptr(unique_ptr<_Yp, _Dp>&& __r) : __ptr_(__r.get()) {
-#if _LIBCPP_STD_VER >= 14
-    if (__ptr_ == nullptr)
-      __cntrl_ = nullptr;
-    else
-#endif
-    {
-      typedef typename __shared_ptr_default_allocator<_Yp>::type _AllocT;
-      typedef __shared_ptr_pointer<typename unique_ptr<_Yp, _Dp>::pointer, _Dp, _AllocT> _CntrlBlk;
-      __cntrl_ = new _CntrlBlk(__r.get(), std::move(__r.get_deleter()), _AllocT());
-      __enable_weak_this(__r.get(), __r.get());
-    }
-    __r.release();
-  }
+    using _AllocT   = typename __shared_ptr_default_allocator<_Yp>::type;
+    using _Deleter  = _If<is_lvalue_reference<_Dp>::value, reference_wrapper<__libcpp_remove_reference_t<_Dp> >, _Dp>;
+    using _CntrlBlk = __shared_ptr_pointer<typename unique_ptr<_Yp, _Dp>::pointer, _Deleter, _AllocT>;
 
-  template <class _Yp,
-            class _Dp,
-            class              = void,
-            __enable_if_t<is_lvalue_reference<_Dp>::value && __compatible_with<_Yp, _Tp>::value &&
-                              is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, element_type*>::value,
-                          int> = 0>
-  _LIBCPP_HIDE_FROM_ABI shared_ptr(unique_ptr<_Yp, _Dp>&& __r) : __ptr_(__r.get()) {
-#if _LIBCPP_STD_VER >= 14
-    if (__ptr_ == nullptr)
-      __cntrl_ = nullptr;
-    else
-#endif
-    {
-      typedef typename __shared_ptr_default_allocator<_Yp>::type _AllocT;
-      typedef __shared_ptr_pointer<typename unique_ptr<_Yp, _Dp>::pointer,
-                                   reference_wrapper<__libcpp_remove_reference_t<_Dp> >,
-                                   _AllocT>
-          _CntrlBlk;
-      __cntrl_ = new _CntrlBlk(__r.get(), std::ref(__r.get_deleter()), _AllocT());
-      __enable_weak_this(__r.get(), __r.get());
-    }
+    __cntrl_ = __ptr_ ? new _CntrlBlk(__r.get(), std::forward<_Dp>(__r.get_deleter()), _AllocT()) : nullptr;
+    __enable_weak_this(__r.get(), __r.get());
     __r.release();
   }
 
diff --git a/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.const/unique_ptr.pass.cpp b/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.const/unique_ptr.pass.cpp
index 9308bb3858c65..f9562627fe122 100644
--- a/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.const/unique_ptr.pass.cpp
+++ b/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.const/unique_ptr.pass.cpp
@@ -12,6 +12,8 @@
 
 // template <class Y, class D> shared_ptr(unique_ptr<Y, D>&&r);
 
+// XFAIL: FROZEN-CXX03-HEADERS-FIXME
+
 #include <memory>
 #include <new>
 #include <cstdlib>
@@ -165,12 +167,10 @@ int main(int, char**)
     { // LWG 2399
         fn(std::unique_ptr<int>(new int));
     }
-#if TEST_STD_VER >= 14
     { // LWG 2415
         std::unique_ptr<int, void (*)(int*)> p(nullptr, assert_deleter<int>);
         std::shared_ptr<int> p2(std::move(p)); // should not call deleter when going out of scope
     }
-#endif
 
     {
     adl::D d;