Use std::addressof for taking an address instead of operator& in moc

Moc shouldn't artificially introduce calls to possibly overloaded
operator&. It can cause odd side effects in a user code.

Change-Id: Iaa1b491fe6a1a5ebd4dfa1172359dc792cc7604f
Fixes: QTBUG-68191
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

3 files changed, 34 insertions, 5 deletions

diff --git a/src/tools/moc/generator.cpp b/src/tools/moc/generator.cpp
index 9fb980893f..c8882343f4 100644
--- a/src/tools/moc/generator.cpp
+++ b/src/tools/moc/generator.cpp
@@ -1549,16 +1549,16 @@ void Generator::generateSignal(FunctionDef *def,int index)
         fprintf(out, "nullptr");
     } else {
         if (def->returnTypeIsVolatile)
-             fprintf(out, "const_cast<void*>(reinterpret_cast<const volatile void*>(&_t0))");
+             fprintf(out, "const_cast<void*>(reinterpret_cast<const volatile void*>(std::addressof(_t0)))");
         else
-             fprintf(out, "const_cast<void*>(reinterpret_cast<const void*>(&_t0))");
+             fprintf(out, "const_cast<void*>(reinterpret_cast<const void*>(std::addressof(_t0)))");
     }
     int i;
     for (i = 1; i < offset; ++i)
         if (i <= def->arguments.count() && def->arguments.at(i - 1).type.isVolatile)
-            fprintf(out, ", const_cast<void*>(reinterpret_cast<const volatile void*>(&_t%d))", i);
+            fprintf(out, ", const_cast<void*>(reinterpret_cast<const volatile void*>(std::addressof(_t%d)))", i);
         else
-            fprintf(out, ", const_cast<void*>(reinterpret_cast<const void*>(&_t%d))", i);
+            fprintf(out, ", const_cast<void*>(reinterpret_cast<const void*>(std::addressof(_t%d)))", i);
     fprintf(out, " };\n");
     fprintf(out, "    QMetaObject::activate(%s, &staticMetaObject, %d, _a);\n", thisPtr.constData(), index);
     if (def->normalizedType != "void")
diff --git a/src/tools/moc/moc.cpp b/src/tools/moc/moc.cpp
index 61a5542c83..76816960ff 100644
--- a/src/tools/moc/moc.cpp
+++ b/src/tools/moc/moc.cpp
@@ -992,7 +992,7 @@ void Moc::generate(FILE *out)
     fprintf(out, "** WARNING! All changes made in this file will be lost!\n"
             "*****************************************************************************/\n\n");
 
-
+    fprintf(out, "#include <memory>\n");  // For std::addressof
     if (!noInclude) {
         if (includePath.size() && !includePath.endsWith('/'))
             includePath += '/';
diff --git a/tests/auto/tools/moc/tst_moc.cpp b/tests/auto/tools/moc/tst_moc.cpp
index 92a94055a4..f1888aebab 100644
--- a/tests/auto/tools/moc/tst_moc.cpp
+++ b/tests/auto/tools/moc/tst_moc.cpp
@@ -682,6 +682,7 @@ private slots:
     void finalClasses();
     void explicitOverrideControl_data();
     void explicitOverrideControl();
+    void overloadedAddressOperator();
     void autoPropertyMetaTypeRegistration();
     void autoMethodArgumentMetaTypeRegistration();
     void autoSignalSpyMetaTypeRegistration();
@@ -2939,6 +2940,34 @@ void tst_Moc::explicitOverrideControl()
 #endif
 }
 
+class OverloadedAddressOperator : public QObject
+{
+   Q_OBJECT
+public:
+   void* operator&() { return nullptr; }
+signals:
+   void self(OverloadedAddressOperator&);
+public slots:
+    void assertSelf(OverloadedAddressOperator &o)
+    {
+        QCOMPARE(std::addressof(o), this);
+        testResult = (std::addressof(o) == this);
+    }
+public:
+    bool testResult = false;
+};
+
+void tst_Moc::overloadedAddressOperator()
+{
+    OverloadedAddressOperator o;
+    OverloadedAddressOperator *p = std::addressof(o);
+    QCOMPARE(&o, nullptr);
+    QVERIFY(p);
+    QObject::connect(p, &OverloadedAddressOperator::self, p, &OverloadedAddressOperator::assertSelf);
+    emit o.self(o);
+    QVERIFY(o.testResult);
+}
+
 class CustomQObject : public QObject
 {
     Q_OBJECT