Enable Q_OBJECT usage across DLL boundary on Symbian OS

Symbian loader does not allow DLL import relocations in the data
section. To workaround this, added an accessor function which can be
used to get the class static metadata from the base class even if it is
in another DLL.

Changing the implementation for all platforms would cause a binary
break, so it is only used for Symbian. The Q_NO_DATA_RELOCATION macro
is used to configure this feature instead of Q_OS_SYMBIAN, because
it is possible another platform may need the same fix and Symbian may
eventually fix their DLL loader to support this feature.

Task-number: 258893
Reviewed-by: Kent Hansen

4 files changed, 44 insertions, 7 deletions

diff --git a/src/corelib/global/qglobal.h b/src/corelib/global/qglobal.h
index 93cc30f..fbefe7a 100644
--- a/src/corelib/global/qglobal.h
+++ b/src/corelib/global/qglobal.h
@@ -2382,6 +2382,10 @@ QT3_SUPPORT Q_CORE_EXPORT const char *qInstallPathSysconf();
 #endif
 
 #if defined(Q_OS_SYMBIAN)
+
+//Symbian does not support data imports from a DLL
+#define Q_NO_DATA_RELOCATION
+
 QT_END_NAMESPACE
 // forward declare std::exception
 #ifdef __cplusplus
diff --git a/src/corelib/kernel/qmetaobject.cpp b/src/corelib/kernel/qmetaobject.cpp
index 3d26160..5771feb 100644
--- a/src/corelib/kernel/qmetaobject.cpp
+++ b/src/corelib/kernel/qmetaobject.cpp
@@ -613,16 +613,26 @@ static const QMetaObject *QMetaObject_findMetaObject(const QMetaObject *self, co
         if (strcmp(self->d.stringdata, name) == 0)
             return self;
         if (self->d.extradata) {
+#ifdef Q_NO_DATA_RELOCATION
+            const QMetaObjectAccessor *e;
+            Q_ASSERT(priv(self->d.data)->revision >= 2);
+#else
             const QMetaObject **e;
             if (priv(self->d.data)->revision < 2) {
                 e = (const QMetaObject**)(self->d.extradata);
-            } else {
+            } else
+#endif
+            {
                 const QMetaObjectExtraData *extra = (const QMetaObjectExtraData*)(self->d.extradata);
                 e = extra->objects;
             }
             if (e) {
                 while (*e) {
+#ifdef Q_NO_DATA_RELOCATION
+                    if (const QMetaObject *m =QMetaObject_findMetaObject(&((*e)()), name))
+#else
                     if (const QMetaObject *m =QMetaObject_findMetaObject((*e), name))
+#endif
                         return m;
                     ++e;
                 }
diff --git a/src/corelib/kernel/qobjectdefs.h b/src/corelib/kernel/qobjectdefs.h
index 421617a..3f990a3 100644
--- a/src/corelib/kernel/qobjectdefs.h
+++ b/src/corelib/kernel/qobjectdefs.h
@@ -150,6 +150,7 @@ inline void qYouForgotTheQ_OBJECT_Macro(T1, T2) {}
 public: \
     Q_OBJECT_CHECK \
     static const QMetaObject staticMetaObject; \
+    static const QMetaObject &getStaticMetaObject(); \
     virtual const QMetaObject *metaObject() const; \
     virtual void *qt_metacast(const char *); \
     QT_TR_FUNCTIONS \
@@ -161,6 +162,7 @@ private:
 #define Q_GADGET \
 public: \
     static const QMetaObject staticMetaObject; \
+    static const QMetaObject &getStaticMetaObject(); \
 private:
 #else // Q_MOC_RUN
 #define slots slots
@@ -444,9 +446,15 @@ struct Q_CORE_EXPORT QMetaObject
 
 };
 
+typedef const QMetaObject& (*QMetaObjectAccessor)();
+
 struct QMetaObjectExtraData
 {
+#ifdef Q_NO_DATA_RELOCATION
+    const QMetaObjectAccessor *objects;
+#else
     const QMetaObject **objects;
+#endif
     int (*static_metacall)(QMetaObject::Call, int, void **);
 };
 
diff --git a/src/tools/moc/generator.cpp b/src/tools/moc/generator.cpp
index cc6fa88..95e8386 100644
--- a/src/tools/moc/generator.cpp
+++ b/src/tools/moc/generator.cpp
@@ -302,13 +302,18 @@ void Generator::generateCode()
         }
     }
     if (!extraList.isEmpty()) {
+        fprintf(out, "#ifdef Q_NO_DATA_RELOCATION\n");
+        fprintf(out, "static const QMetaObjectAccessor qt_meta_extradata_%s[] = {\n    ", qualifiedClassNameIdentifier.constData());
+        for (int i = 0; i < extraList.count(); ++i) {
+            fprintf(out, "    %s::getStaticMetaObject,\n", extraList.at(i).constData());
+        }
+        fprintf(out, "#else\n");
         fprintf(out, "static const QMetaObject *qt_meta_extradata_%s[] = {\n    ", qualifiedClassNameIdentifier.constData());
         for (int i = 0; i < extraList.count(); ++i) {
-            if (i)
-                fprintf(out, ",\n    ");
-            fprintf(out, "    &%s::staticMetaObject", extraList.at(i).constData());
+            fprintf(out, "    &%s::staticMetaObject,\n", extraList.at(i).constData());
         }
-        fprintf(out, ",0\n};\n\n");
+        fprintf(out, "#endif //Q_NO_DATA_RELOCATION\n");
+        fprintf(out, "    0\n};\n\n");
     }
 
     if (isConstructible || !extraList.isEmpty()) {
@@ -328,7 +333,6 @@ void Generator::generateCode()
 //
 // Finally create and initialize the static meta object
 //
-
     if (isQt)
         fprintf(out, "const QMetaObject QObject::staticQtMetaObject = {\n");
     else
@@ -348,11 +352,22 @@ void Generator::generateCode()
         fprintf(out, "&qt_meta_extradata2_%s }\n", qualifiedClassNameIdentifier.constData());
     fprintf(out, "};\n");
 
-    if (isQt || !cdef->hasQObject)
+    if(isQt)
+        return;
+
+//
+// Generate static meta object accessor (needed for symbian, because DLLs do not support data imports.
+//
+    fprintf(out, "\n#ifdef Q_NO_DATA_RELOCATION\n");
+    fprintf(out, "const QMetaObject &%s::getStaticMetaObject() { return staticMetaObject; }\n", cdef->qualified.constData());
+    fprintf(out, "#endif //Q_NO_DATA_RELOCATION\n");
+
+    if (!cdef->hasQObject)
         return;
 
     fprintf(out, "\nconst QMetaObject *%s::metaObject() const\n{\n    return QObject::d_ptr->metaObject ? QObject::d_ptr->metaObject : &staticMetaObject;\n}\n",
             cdef->qualified.constData());
+
 //
 // Generate smart cast function
 //