Detect incompatibilities in repeated type registration

QMetaType used to register a typeName and factory functions for
creation/destruction of objects. While it would be possible for a single
type name to be registered matching different actual types and memory
layouts, there was little that could be done about it.

Now that QMetaType is tracking type information with a direct impact on
data layout and ABI (size and type flags) it is important that we check
and detect binary incompatibilities as early as possible.

[Such incompatibilities could arise from type name re-use (technically,
ODR violations) or, more commonly, as version mismatch between different
shared libraries or plugins.]

Only type size and flags are checked as function pointers to inline and
template or otherwise non-exported functions could trivially differ
across translation units and shared libraries.

When registering typedef types, a check is made to ensure the same name
doesn't get registered as different types.

Change-Id: I8211c3de75d4854ce8fafdb620d3a931c206e0c3
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@nokia.com>
Reviewed-by: Kent Hansen <kent.hansen@nokia.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp b/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp
index ca2964d3e2..f90e7f463f 100644
--- a/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp
+++ b/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp
@@ -85,6 +85,7 @@ private slots:
     void constructCopy_data();
     void constructCopy();
     void typedefs();
+    void registerType();
     void isRegistered_data();
     void isRegistered();
     void registerStreamBuiltin();
@@ -828,6 +829,44 @@ void tst_QMetaType::typedefs()
     QCOMPARE(QMetaType::type("WhityDouble"), ::qMetaTypeId<WhityDouble>());
 }
 
+void tst_QMetaType::registerType()
+{
+    // Built-in
+    QCOMPARE(qRegisterMetaType<QString>("QString"), int(QMetaType::QString));
+    QCOMPARE(qRegisterMetaType<QString>("QString"), int(QMetaType::QString));
+
+    // Custom
+    int fooId = qRegisterMetaType<TestSpace::Foo>("TestSpace::Foo");
+    QVERIFY(fooId >= int(QMetaType::User));
+    QCOMPARE(qRegisterMetaType<TestSpace::Foo>("TestSpace::Foo"), fooId);
+
+    int movableId = qRegisterMetaType<CustomMovable>("CustomMovable");
+    QVERIFY(movableId >= int(QMetaType::User));
+    QCOMPARE(qRegisterMetaType<CustomMovable>("CustomMovable"), movableId);
+
+    // Alias to built-in
+    typedef QString MyString;
+
+    QCOMPARE(qRegisterMetaType<MyString>("MyString"), int(QMetaType::QString));
+    QCOMPARE(qRegisterMetaType<MyString>("MyString"), int(QMetaType::QString));
+
+    QCOMPARE(QMetaType::type("MyString"), int(QMetaType::QString));
+
+    // Alias to custom type
+    typedef CustomMovable MyMovable;
+    typedef TestSpace::Foo MyFoo;
+
+    QCOMPARE(qRegisterMetaType<MyMovable>("MyMovable"), movableId);
+    QCOMPARE(qRegisterMetaType<MyMovable>("MyMovable"), movableId);
+
+    QCOMPARE(QMetaType::type("MyMovable"), movableId);
+
+    QCOMPARE(qRegisterMetaType<MyFoo>("MyFoo"), fooId);
+    QCOMPARE(qRegisterMetaType<MyFoo>("MyFoo"), fooId);
+
+    QCOMPARE(QMetaType::type("MyFoo"), fooId);
+}
+
 class IsRegisteredDummyType { };
 
 void tst_QMetaType::isRegistered_data()