AK+Everywhere: Move custom deleter capability to OwnPtr

`OwnPtrWithCustomDeleter` was a decorator which provided the ability
to add a custom deleter to `OwnPtr` by wrapping and taking the deleter
as a run-time argument to the constructor. This solution means that no
additional space is needed for the `OwnPtr` because it doesn't need to
store a pointer to the deleter, but comes at the cost of having an
extra type that stores a pointer for every instance.

This logic is moved directly into `OwnPtr` by adding a template
argument that is defaulted to the default deleter for the type. This
means that the type itself stores the pointer to the deleter instead
of every instance and adds some type safety by encoding the deleter in
the type itself instead of taking a run-time argument.

AK/DefaultDelete.h

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2022, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+namespace AK {
+
+template<class T>
+struct DefaultDelete {
+    constexpr DefaultDelete() = default;
+
+    constexpr void operator()(T* t)
+    {
+        delete t;
+    }
+};
+
+template<class T>
+struct DefaultDelete<T[]> {
+    constexpr DefaultDelete() = default;
+
+    constexpr void operator()(T* t)
+    {
+        delete[] t;
+    }
+};
+
+}
+
+#ifdef USING_AK_GLOBALLY
+using AK::DefaultDelete;
+#endif

AK/Forward.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <AK/DefaultDelete.h>
 #include <AK/Types.h>
 
 namespace AK {
@@ -133,7 +134,7 @@ class LockRefPtr;
 template<typename T>
 class RefPtr;
 
-template<typename T>
+template<typename T, typename TDeleter = DefaultDelete<T>>
 class OwnPtr;
 
 template<typename T>

AK/NonnullRefPtr.h

@@ -16,8 +16,6 @@
 
 namespace AK {
 
-template<typename T>
-class OwnPtr;
 template<typename T>
 class RefPtr;
 

AK/OwnPtr.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <AK/Error.h>
+#include <AK/Forward.h>
 #include <AK/NonnullOwnPtr.h>
 #include <AK/RefCounted.h>
 
@@ -14,7 +15,7 @@
 
 namespace AK {
 
-template<typename T>
+template<typename T, typename TDeleter>
 class [[nodiscard]] OwnPtr {
 public:
     OwnPtr() = default;
@@ -105,7 +106,7 @@ public:
 
     void clear()
     {
-        delete m_ptr;
+        TDeleter {}(m_ptr);
         m_ptr = nullptr;
     }
 

AK/OwnPtrWithCustomDeleter.h

@@ -1,41 +0,0 @@
-/*
- * Copyright (c) 2022, Lucas Chollet <[email protected]>
- *
- * SPDX-License-Identifier: BSD-2-Clause
- */
-
-#pragma once
-
-#include <AK/Function.h>
-#include <AK/Noncopyable.h>
-#include <AK/StdLibExtras.h>
-
-template<typename T>
-struct OwnPtrWithCustomDeleter {
-    AK_MAKE_NONCOPYABLE(OwnPtrWithCustomDeleter);
-
-public:
-    OwnPtrWithCustomDeleter(T* ptr, Function<void(T*)> deleter)
-        : m_ptr(ptr)
-        , m_deleter(move(deleter))
-    {
-    }
-
-    OwnPtrWithCustomDeleter(OwnPtrWithCustomDeleter&& other)
-    {
-        swap(m_ptr, other.m_ptr);
-        swap(m_deleter, other.m_deleter);
-    };
-
-    ~OwnPtrWithCustomDeleter()
-    {
-        if (m_ptr) {
-            VERIFY(m_deleter);
-            m_deleter(m_ptr);
-        }
-    }
-
-private:
-    T* m_ptr { nullptr };
-    Function<void(T*)> m_deleter {};
-};

AK/RefPtr.h

@@ -12,6 +12,7 @@
 #include <AK/Atomic.h>
 #include <AK/Error.h>
 #include <AK/Format.h>
+#include <AK/Forward.h>
 #include <AK/NonnullRefPtr.h>
 #include <AK/StdLibExtras.h>
 #include <AK/Traits.h>
@@ -19,9 +20,6 @@
 
 namespace AK {
 
-template<typename T>
-class OwnPtr;
-
 template<typename T>
 class [[nodiscard]] RefPtr {
     template<typename U>

Kernel/Library/LockRefPtr.h

@@ -23,9 +23,6 @@
 
 namespace AK {
 
-template<typename T>
-class OwnPtr;
-
 template<typename T>
 struct LockRefPtrTraits {
     ALWAYS_INLINE static T* as_ptr(FlatPtr bits)

Kernel/Library/NonnullLockRefPtr.h

@@ -21,8 +21,6 @@
 
 namespace AK {
 
-template<typename T>
-class OwnPtr;
 template<typename T, typename PtrTraits>
 class LockRefPtr;
 

Tests/AK/CMakeLists.txt

@@ -52,6 +52,7 @@ set(AK_TEST_SOURCES
     TestNonnullRefPtr.cpp
     TestNumberFormat.cpp
     TestOptional.cpp
+    TestOwnPtr.cpp
     TestPrint.cpp
     TestQueue.cpp
     TestQuickSort.cpp

Tests/AK/TestOwnPtr.cpp

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2022, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibTest/TestCase.h>
+
+#include <AK/OwnPtr.h>
+
+static u64 deleter_call_count = 0;
+
+TEST_CASE(should_call_custom_deleter)
+{
+    auto deleter = [](auto* p) { if (p) ++deleter_call_count; };
+    auto ptr = OwnPtr<u64, decltype(deleter)> {};
+    ptr.clear();
+    EXPECT_EQ(0u, deleter_call_count);
+    ptr = adopt_own_if_nonnull(&deleter_call_count);
+    EXPECT_EQ(0u, deleter_call_count);
+    ptr.clear();
+    EXPECT_EQ(1u, deleter_call_count);
+}

Userland/Libraries/LibCore/System.cpp

@@ -1334,11 +1334,7 @@ ErrorOr<AddressInfoVector> getaddrinfo(char const* nodename, char const* servnam
     for (auto* result = results; result != nullptr; result = result->ai_next)
         TRY(addresses.try_append(*result));
 
-    return AddressInfoVector { move(addresses), results,
-        [](struct addrinfo* ptr) {
-            if (ptr)
-                ::freeaddrinfo(ptr);
-        } };
+    return AddressInfoVector { move(addresses), results };
 }
 
 ErrorOr<void> getsockopt(int sockfd, int level, int option, void* value, socklen_t* value_size)

Userland/Libraries/LibCore/System.h

@@ -10,7 +10,7 @@
 
 #include <AK/Error.h>
 #include <AK/Noncopyable.h>
-#include <AK/OwnPtrWithCustomDeleter.h>
+#include <AK/OwnPtr.h>
 #include <AK/StringView.h>
 #include <AK/Vector.h>
 #include <dirent.h>
@@ -226,14 +226,18 @@ public:
 private:
     friend ErrorOr<AddressInfoVector> getaddrinfo(char const* nodename, char const* servname, struct addrinfo const& hints);
 
-    AddressInfoVector(Vector<struct addrinfo>&& addresses, struct addrinfo* ptr, AK::Function<void(struct addrinfo*)> deleter)
+    AddressInfoVector(Vector<struct addrinfo>&& addresses, struct addrinfo* ptr)
         : m_addresses(move(addresses))
-        , m_ptr(ptr, move(deleter))
+        , m_ptr(adopt_own_if_nonnull(ptr))
     {
     }
 
+    struct AddrInfoDeleter {
+        void operator()(struct addrinfo* ptr) { ::freeaddrinfo(ptr); }
+    };
+
     Vector<struct addrinfo> m_addresses {};
-    OwnPtrWithCustomDeleter<struct addrinfo> m_ptr;
+    OwnPtr<struct addrinfo, AddrInfoDeleter> m_ptr {};
 };
 
 ErrorOr<AddressInfoVector> getaddrinfo(char const* nodename, char const* servname, struct addrinfo const& hints);