From 99d401220c3b200e76f00cb7457a5a3935379572 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B8ger=20Hanseg=C3=A5rd?= <joger.hansegard@qt.io>
Date: Thu, 2 Jan 2025 15:31:43 +0100
Subject: [PATCH] Compare QUniqueHandles using comparesEqual and
 compareThreeWay

This fixes an issue where comparing pointers to object is only defined
if both pointers point into the same array.

Task-number: QTBUG-132507
Pick-to: 6.8
Change-Id: Ib7ccb30001add38ad25b62c848a01cd53566d8bf
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 5dcdeeebbc08be8845cdb5a0e586b7a864b7f16f)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/corelib/tools/quniquehandle_p.h           | 34 +++++----------
 .../tools/quniquehandle/tst_quniquehandle.cpp | 42 +++++++++++++++++++
 2 files changed, 53 insertions(+), 23 deletions(-)

diff --git a/src/corelib/tools/quniquehandle_p.h b/src/corelib/tools/quniquehandle_p.h
index c746e51fe72..3ba557e838d 100644
--- a/src/corelib/tools/quniquehandle_p.h
+++ b/src/corelib/tools/quniquehandle_p.h
@@ -17,6 +17,7 @@
 
 #include <QtCore/qtconfigmacros.h>
 #include <QtCore/qassert.h>
+#include <QtCore/qcompare.h>
 #include <QtCore/qswap.h>
 #include <QtCore/qtclasshelpermacros.h>
 
@@ -198,37 +199,24 @@ public:
         m_handle = HandleTraits::invalidValue();
     }
 
-    [[nodiscard]] friend bool operator==(const QUniqueHandle &lhs, const QUniqueHandle &rhs) noexcept
+private:
+    friend bool comparesEqual(const QUniqueHandle& lhs, const QUniqueHandle& rhs) noexcept
     {
         return lhs.get() == rhs.get();
     }
 
-    [[nodiscard]] friend bool operator!=(const QUniqueHandle &lhs, const QUniqueHandle &rhs) noexcept
+    friend Qt::strong_ordering compareThreeWay(const QUniqueHandle& lhs,
+                                               const QUniqueHandle& rhs) noexcept
     {
-        return lhs.get() != rhs.get();
+        if constexpr (std::is_pointer_v<Type>)
+            return qCompareThreeWay(Qt::totally_ordered_wrapper{ lhs.get() },
+                                    Qt::totally_ordered_wrapper{ rhs.get() });
+        else
+            return qCompareThreeWay(lhs.get(), rhs.get());
     }
 
-    [[nodiscard]] friend bool operator<(const QUniqueHandle &lhs, const QUniqueHandle &rhs) noexcept
-    {
-        return lhs.get() < rhs.get();
-    }
+    Q_DECLARE_STRONGLY_ORDERED(QUniqueHandle)
 
-    [[nodiscard]] friend bool operator<=(const QUniqueHandle &lhs, const QUniqueHandle &rhs) noexcept
-    {
-        return lhs.get() <= rhs.get();
-    }
-
-    [[nodiscard]] friend bool operator>(const QUniqueHandle &lhs, const QUniqueHandle &rhs) noexcept
-    {
-        return lhs.get() > rhs.get();
-    }
-
-    [[nodiscard]] friend bool operator>=(const QUniqueHandle &lhs, const QUniqueHandle &rhs) noexcept
-    {
-        return lhs.get() >= rhs.get();
-    }
-
-private:
     Type m_handle{ HandleTraits::invalidValue() };
 };
 
diff --git a/tests/auto/corelib/tools/quniquehandle/tst_quniquehandle.cpp b/tests/auto/corelib/tools/quniquehandle/tst_quniquehandle.cpp
index 448ea0964fb..a23b2132d66 100644
--- a/tests/auto/corelib/tools/quniquehandle/tst_quniquehandle.cpp
+++ b/tests/auto/corelib/tools/quniquehandle/tst_quniquehandle.cpp
@@ -348,6 +348,48 @@ private slots:
         QCOMPARE_EQ(Handle{ }, Handle{ });
     }
 
+    void comparison_behavesAsPointer_whenHandleTypeIsPointer_data() const
+    {
+        QTest::addColumn<int*>("lhs");
+        QTest::addColumn<int*>("rhs");
+
+        QTest::addRow("lhs == rhs") << reinterpret_cast<int*>(2) << reinterpret_cast<int*>(2);
+        QTest::addRow("lhs < rhs") << reinterpret_cast<int*>(1) << reinterpret_cast<int*>(2);
+        QTest::addRow("lhs > rhs") << reinterpret_cast<int*>(2) << reinterpret_cast<int*>(1);
+    }
+
+    void comparison_behavesAsPointer_whenHandleTypeIsPointer() const
+    {
+        struct IntPtrTraits
+        {
+            using Type = int*;
+
+            static bool close(Type)
+            {
+                return true;
+            }
+
+            static Type invalidValue() noexcept
+            {
+                return nullptr;
+            }
+        };
+
+        using Handle = QUniqueHandle<IntPtrTraits>;
+
+        QFETCH(int*, lhs);
+        QFETCH(int*, rhs);
+
+        QCOMPARE_EQ(Handle{ lhs } == Handle{ rhs }, lhs == rhs);
+        QCOMPARE_EQ(Handle{ lhs } != Handle{ rhs }, lhs != rhs);
+        QCOMPARE_EQ(Handle{ lhs } < Handle{ rhs }, lhs < rhs);
+        QCOMPARE_EQ(Handle{ lhs } <= Handle{ rhs }, lhs <= rhs);
+        QCOMPARE_EQ(Handle{ lhs } > Handle{ rhs }, lhs > rhs);
+        QCOMPARE_EQ(Handle{ lhs } >= Handle{ rhs },  lhs >= rhs);
+
+        QCOMPARE_EQ(Handle{ }, Handle{ });
+    }
+
     void sort_sortsHandles() const
     {
         const auto resource0 = GlobalResource::open();