From 7a758c0e1c4fe1d47e8f7bc2c3a1261ffca24bdb Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Thu, 23 Jul 2026 01:50:51 +0200
Subject: kstd: add test for aliasing shared_ptr ctor

---
 libs/kstd/kstd/bits/shared_ptr.hpp       |  1 -
 libs/kstd/kstd/bits/shared_ptr.tests.cpp | 61 ++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 1 deletion(-)
 create mode 100644 libs/kstd/kstd/bits/shared_ptr.tests.cpp

(limited to 'libs/kstd')

diff --git a/libs/kstd/kstd/bits/shared_ptr.hpp b/libs/kstd/kstd/bits/shared_ptr.hpp
index 1171d7fe..34332ace 100644
--- a/libs/kstd/kstd/bits/shared_ptr.hpp
+++ b/libs/kstd/kstd/bits/shared_ptr.hpp
@@ -392,7 +392,6 @@ namespace kstd
     //! @param other The shared_ptr to share ownership with.
     //! @param pointer The pointer this shared_ptr should own.
     template<typename Y>
-      requires bits::is_shared_pointer_ctor_compatible<T *, Y *>::value
     shared_ptr(shared_ptr<Y> const & other, T * pointer) noexcept
         : m_storage{pointer}
         , m_control_block{other.m_control_block}
diff --git a/libs/kstd/kstd/bits/shared_ptr.tests.cpp b/libs/kstd/kstd/bits/shared_ptr.tests.cpp
new file mode 100644
index 00000000..cf63e0aa
--- /dev/null
+++ b/libs/kstd/kstd/bits/shared_ptr.tests.cpp
@@ -0,0 +1,61 @@
+#include <kstd/bits/shared_ptr.hpp>
+
+#include <catch2/catch_test_macros.hpp>
+
+namespace
+{
+
+  struct base  // NOLINT(cppcoreguidelines-virtual-class-destructor)
+  {
+    [[nodiscard]] virtual auto id() const noexcept -> int
+    {
+      return 1;
+    }
+  };
+
+  struct derived final : base
+  {
+    [[nodiscard]] auto id() const noexcept -> int override
+    {
+      return 2;
+    }
+  };
+
+}  // namespace
+
+SCENARIO("Shared pointer casts", "[kstd][shared_ptr]")
+{
+  GIVEN("a shared_ptr<derived>")
+  {
+    auto derived_ptr = kstd::make_shared<derived>();
+
+    WHEN("casting it to a shared_ptr<base> via static_pointer_cast")
+    {
+      auto base_ptr = kstd::static_pointer_cast<base>(derived_ptr);
+
+      THEN("both pointer observer the same, still-derived object")
+      {
+        REQUIRE(base_ptr.get() == static_cast<base *>(derived_ptr.get()));
+        REQUIRE(base_ptr->id() == 2);
+      }
+
+      THEN("ownership is shared")
+      {
+        REQUIRE(derived_ptr.use_count() == 2);
+        REQUIRE(base_ptr.use_count() == 2);
+      }
+
+      AND_WHEN("the original shared pointer is reset")
+      {
+        derived_ptr.reset();
+
+        THEN("the object is kept alive by the aliased base shared pointer")
+        {
+          REQUIRE(base_ptr);
+          REQUIRE(base_ptr->id() == 2);
+          REQUIRE(base_ptr.use_count() == 1);
+        }
+      }
+    }
+  }
+}
-- 
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