Fix crash related to multiple inheritance

In the <class>_PTR_CppToPython_<class> converter function (written by
CppGenerator::writeConverterFunctions()), the generated code
used typeid(*ptr).name() to retrieve the name to use for the
SbkObjectTypes. This construct returns the name of the outermost
class (for example, "QWidget" for a QWidget-type paint device returned
by QPainter::device()), as opposed to "QPaintDevice *" returned by
typeid(ptr).name(). This caused a crash with multiple inheritance
since QWidget inherits QObject and QPaintDevice and the "QWidget"
type was associated with the QPaintDevice pointer.

To fix this:
- Add API to libshiboken to obtain the SbkObjectType* by name
  and check for the presence of a special cast function (multiple
  inheritance).
- Generate the code of <class>_PTR_CppToPython_<class> as follows:
  Check whether the outermost type obtained by typeid(*ptr).name()
  has a special cast function. If that is the case, use the
  type name obtained by typeid(ptr).name() (base class) to create
  the wrapper.

Change-Id: I8ee6b4c084e9dafa434623433661809b83aedee5
Fixes: PYSIDE-868
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>

4 files changed, 80 insertions, 16 deletions

diff --git a/sources/shiboken2/generator/shiboken2/cppgenerator.cpp b/sources/shiboken2/generator/shiboken2/cppgenerator.cpp
index e46e0b968..9df0d61c5 100644
--- a/sources/shiboken2/generator/shiboken2/cppgenerator.cpp
+++ b/sources/shiboken2/generator/shiboken2/cppgenerator.cpp
@@ -50,6 +50,30 @@ QHash<QString, QString> CppGenerator::m_sqFuncs = QHash<QString, QString>();
 QHash<QString, QString> CppGenerator::m_mpFuncs = QHash<QString, QString>();
 QString CppGenerator::m_currentErrorCode(QLatin1String("0"));
 
+static const char typeNameFunc[] = R"CPP(
+template <class T>
+static const char *typeNameOf(const T &t)
+{
+    const char *typeName =  typeid(t).name();
+    auto size = std::strlen(typeName);
+#if defined(Q_CC_MSVC) // MSVC: "class QPaintDevice * __ptr64"
+    if (auto lastStar = strchr(typeName, '*')) {
+        // MSVC: "class QPaintDevice * __ptr64"
+        while (*--lastStar == ' ') {
+        }
+        size = lastStar - typeName + 1;
+    }
+#else // g++, Clang: "QPaintDevice *" -> "P12QPaintDevice"
+    if (size > 2 && typeName[0] == 'P' && std::isdigit(typeName[1]))
+        ++typeName;
+#endif
+    char *result = new char[size + 1];
+    result[size] = '\0';
+    strncpy(result, typeName, size);
+    return result;
+}
+)CPP";
+
 // utility functions
 inline AbstractMetaType* getTypeWithoutContainer(AbstractMetaType* arg)
 {
@@ -336,6 +360,8 @@ void CppGenerator::generateClass(QTextStream &s, GeneratorContext &classContext)
         s << inc.toString() << endl;
     s << endl;
 
+    s << "\n#include <cctype>\n#include <cstring>\n";
+
     if (metaClass->typeEntry()->typeFlags() & ComplexTypeEntry::Deprecated)
         s << "#Deprecated" << endl;
 
@@ -351,7 +377,7 @@ void CppGenerator::generateClass(QTextStream &s, GeneratorContext &classContext)
         }
     }
 
-    s << endl;
+    s << endl << endl << typeNameFunc << endl;
 
     // Create string literal for smart pointer getter method.
     if (classContext.forSmartPointer()) {
@@ -1226,9 +1252,19 @@ void CppGenerator::writeConverterFunctions(QTextStream &s, const AbstractMetaCla
             c << INDENT << "return pyOut;" << endl;
         }
         c << INDENT << '}' << endl;
-        c << INDENT << "const char* typeName = typeid(*((" << typeName << "*)cppIn)).name();" << endl;
-        c << INDENT << "return Shiboken::Object::newObject(" << cpythonType;
-        c << ", const_cast<void*>(cppIn), false, false, typeName);";
+        c << INDENT   << "bool changedTypeName = false;\n"
+            << INDENT << "auto tCppIn = reinterpret_cast<const " << typeName << " *>(cppIn);\n"
+            << INDENT << "const char *typeName = typeid(*tCppIn).name();\n"
+            << INDENT << "auto sbkType = Shiboken::ObjectType::typeForTypeName(typeName);\n"
+            << INDENT << "if (sbkType && Shiboken::ObjectType::hasSpecialCastFunction(sbkType)) {\n"
+            << INDENT << "    typeName = typeNameOf(tCppIn);\n"
+            << INDENT << "    changedTypeName = true;\n"
+            << INDENT << " }\n"
+            << INDENT << "PyObject *result = Shiboken::Object::newObject(" << cpythonType
+            <<           ", const_cast<void*>(cppIn), false, /* exactType */ changedTypeName, typeName);\n"
+            << INDENT << "if (changedTypeName)\n"
+            << INDENT << "    delete [] typeName;\n"
+            << INDENT << "return result;";
     }
     std::swap(targetTypeName, sourceTypeName);
     writeCppToPythonFunction(s, code, sourceTypeName, targetTypeName);
diff --git a/sources/shiboken2/libshiboken/basewrapper.cpp b/sources/shiboken2/libshiboken/basewrapper.cpp
index c9e3b9d1b..e820e749b 100644
--- a/sources/shiboken2/libshiboken/basewrapper.cpp
+++ b/sources/shiboken2/libshiboken/basewrapper.cpp
@@ -831,6 +831,23 @@ void setTypeUserData(SbkObjectType* type, void* userData, DeleteUserDataFunc d_f
     sotp->d_func = d_func;
 }
 
+// Try to find the exact type of cptr.
+SbkObjectType *typeForTypeName(const char *typeName)
+{
+    SbkObjectType *result{};
+    if (typeName) {
+        if (PyTypeObject *pyType = Shiboken::Conversions::getPythonTypeObject(typeName))
+            result = reinterpret_cast<SbkObjectType*>(pyType);
+    }
+    return result;
+}
+
+bool hasSpecialCastFunction(SbkObjectType *sbkType)
+{
+    const SbkObjectTypePrivate *d = PepType_SOTP(sbkType);
+    return d != nullptr && d->mi_specialcast != nullptr;
+}
+
 } // namespace ObjectType
 
 
@@ -1191,7 +1208,6 @@ SbkObject *findColocatedChild(SbkObject *wrapper,
     return 0;
 }
 
-
 PyObject *newObject(SbkObjectType* instanceType,
                     void* cptr,
                     bool hasOwnership,
@@ -1200,13 +1216,9 @@ PyObject *newObject(SbkObjectType* instanceType,
 {
     // Try to find the exact type of cptr.
     if (!isExactType) {
-        PyTypeObject* exactType = 0;
-        if (typeName) {
-            exactType = Shiboken::Conversions::getPythonTypeObject(typeName);
-            if (exactType)
-                instanceType = reinterpret_cast<SbkObjectType*>(exactType);
-        }
-        if (!exactType)
+        if (SbkObjectType *exactType = ObjectType::typeForTypeName(typeName))
+            instanceType = exactType;
+        else
             instanceType = BindingManager::instance().resolveType(&cptr, instanceType);
     }
 
diff --git a/sources/shiboken2/libshiboken/basewrapper.h b/sources/shiboken2/libshiboken/basewrapper.h
index 65849d783..15682c600 100644
--- a/sources/shiboken2/libshiboken/basewrapper.h
+++ b/sources/shiboken2/libshiboken/basewrapper.h
@@ -238,6 +238,20 @@ LIBSHIBOKEN_API void        setSubTypeInitHook(SbkObjectType* self, SubTypeInitH
 LIBSHIBOKEN_API void*       getTypeUserData(SbkObjectType* self);
 LIBSHIBOKEN_API void        setTypeUserData(SbkObjectType* self, void* userData, DeleteUserDataFunc d_func);
 
+/**
+ * Return an instance of SbkObjectType for a C++ type name as determined by
+ * typeinfo().name().
+ * \param typeName Type name
+ * \since 5.12
+ */
+LIBSHIBOKEN_API SbkObjectType *typeForTypeName(const char *typeName);
+
+/**
+ *  Returns whether SbkObjectType has a special cast function (multiple inheritance)
+ * \param sbkType Sbk type
+ * \since 5.12
+ */
+LIBSHIBOKEN_API bool hasSpecialCastFunction(SbkObjectType *sbkType);
 }
 
 namespace Object {
diff --git a/sources/shiboken2/tests/otherbinding/typediscovery_test.py b/sources/shiboken2/tests/otherbinding/typediscovery_test.py
index 6816b158a..a9eb88d80 100644
--- a/sources/shiboken2/tests/otherbinding/typediscovery_test.py
+++ b/sources/shiboken2/tests/otherbinding/typediscovery_test.py
@@ -51,14 +51,16 @@ class TypeDiscoveryTest(unittest.TestCase):
     def testMultipleInheritance(self):
         obj = OtherMultipleDerived.createObject("Base1");
         self.assertEqual(type(obj), Base1)
+        # PYSIDE-868: In case of multiple inheritance, a factory
+        # function will return the base class wrapper.
         obj = OtherMultipleDerived.createObject("MDerived1");
-        self.assertEqual(type(obj), MDerived1)
+        self.assertEqual(type(obj), Base1)
         obj = OtherMultipleDerived.createObject("SonOfMDerived1");
-        self.assertEqual(type(obj), SonOfMDerived1)
+        self.assertEqual(type(obj), Base1)
         obj = OtherMultipleDerived.createObject("MDerived3");
-        self.assertEqual(type(obj), MDerived3)
+        self.assertEqual(type(obj), Base1)
         obj = OtherMultipleDerived.createObject("OtherMultipleDerived");
-        self.assertEqual(type(obj), OtherMultipleDerived)
+        self.assertEqual(type(obj), Base1)
 
 if __name__ == '__main__':
     unittest.main()