[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 251552cb5577f859d22947d0f8d0f9b81ef22068 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          | 42 +++++--------------
 .../unique_ptr.pass.cpp                       |  2 -
 2 files changed, 11 insertions(+), 33 deletions(-)

diff --git a/libcxx/include/__memory/shared_ptr.h b/libcxx/include/__memory/shared_ptr.h
index e90db587d2836..a14ebd97a43ed 100644
--- a/libcxx/include/__memory/shared_ptr.h
+++ b/libcxx/include/__memory/shared_ptr.h
@@ -487,45 +487,25 @@ 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;
 
-  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;
+    else if _LIBCPP_CONSTEXPR (is_lvalue_reference<_Dp>::value) {
+      using _CntrlBlk =
+          __shared_ptr_pointer<typename unique_ptr<_Yp, _Dp>::pointer,
+                               reference_wrapper<__libcpp_remove_reference_t<_Dp> >,
+                               _AllocT>;
       __cntrl_ = new _CntrlBlk(__r.get(), std::ref(__r.get_deleter()), _AllocT());
-      __enable_weak_this(__r.get(), __r.get());
+    } else {
+      using _CntrlBlk = __shared_ptr_pointer<typename unique_ptr<_Yp, _Dp>::pointer, _Dp, _AllocT>;
+      __cntrl_        = new _CntrlBlk(__r.get(), std::move(__r.get_deleter()), _AllocT());
     }
+    __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..9211e468075d7 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
@@ -165,12 +165,10 @@ 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;