Debugger: Replace 'first base' guessing logic

Use the fact that the order of the first three vtable entries of a QObject is fixed and the size of their implementations is roughly known. Change-Id: I3d13f594cb1c1f162a520da18b2bc2aaba852092 Reviewed-by: Christian Stenger <christian.stenger@qt.io>
2016-11-02 13:04:21 +01:00
parent 63bed77178
commit 3be260ecc5
2 changed files with 42 additions and 26 deletions
@@ -1444,12 +1444,19 @@ class DumperBase:
        else:
            return p > 100000 and (p & 0x7 == 0) and (p < 0x7fffffffffff)

+    def canBeVTableEntry(self, p):
+        if self.ptrSize() == 4:
+            return p > 100000 and (p & 0x1 == 0)
+        else:
+            return p > 100000 and (p & 0x1 == 0) and (p < 0x7fffffffffff)
+
    def couldBeQObject(self, objectPtr):
        try:
            (vtablePtr, dd) = self.split('pp', objectPtr)
        except:
            self.bump('nostruct-1')
            return False
+
        if not self.canBePointer(vtablePtr):
            self.bump('vtable')
            return False
@@ -1457,6 +1464,33 @@ class DumperBase:
            self.bump('d_d_ptr')
            return False

+        try:
+            metaObjectFunc, metaCastFunc, metaCallFunc = self.split('ppp', vtablePtr)
+        except:
+            return False
+
+        # The first three entries are in a fairly rigid relationship defined
+        # by the Q_OBJECT macro.
+        if not self.canBeVTableEntry(metaObjectFunc):
+            return False
+        if not self.canBeVTableEntry(metaCastFunc):
+            return False
+        if not self.canBeVTableEntry(metaCallFunc):
+            return False
+        if metaCastFunc < metaObjectFunc or metaCastFunc > metaObjectFunc + 200:
+            # The metaObject implementation is just that:
+            # QObject::d_ptr->metaObject ? QObject::d_ptr->dynamicMetaObject()
+            #                            : &staticMetaObject;
+            # That should not exceed 200 bytes. Observed on x86_64 debug 72.
+            return False
+        if metaCallFunc < metaCastFunc or metaCallFunc > metaCastFunc + 200:
+            # if (!_clname) return nullptr;
+            # if (!strcmp(_clname, qt_meta_stringdata_Bar__TestObject.stringdata0))
+            #     return static_cast<void*>(const_cast< TestObject*>(this));
+            # return QWidget::qt_metacast(_clname);
+            # That should not exceed 200 bytes. Observed on x86_64 debug 80.
+            return False
+
        try:
            (dvtablePtr, qptr, parentPtr, childrenDPtr, flags) \
                = self.split('ppppI', dd)
@@ -1529,14 +1563,9 @@ class DumperBase:
            typeName = someTypeObj.name
            isQObjectProper = typeName == self.qtNamespace() + 'QObject'

-            if not isQObjectProper:
-                #if someTypeObj.firstBase() is None:
-                #    warn("FIRST BASE IS NONE")
-                #    return 0
-
-                # No templates for now.
-                if typeName.find('<') >= 0:
-                    return 0
+            # No templates for now.
+            if typeName.find('<') >= 0:
+                return 0

            result = self.findStaticMetaObject(typeName)

@@ -1568,10 +1597,10 @@ class DumperBase:
            #except:
            #    warn('METAOBJECT EXTRACTION FAILED FOR UNKNOWN REASON')

-            if not result:
-                base = someTypeObj.firstBase()
-                if base is not None and base != someTypeObj: # sanity check
-                    result = extractStaticMetaObjectPtrFromType(base)
+            #if not result:
+            #    base = someTypeObj.firstBase()
+            #    if base is not None and base != someTypeObj: # sanity check
+            #        result = extractStaticMetaObjectPtrFromType(base)

            self.knownStaticMetaObjects[someTypeName] = result
            return result
@@ -1999,7 +2028,7 @@ class DumperBase:
                self.putItemCount(0)
            else:
                connections = connections.dereference()
-                connections = connections.cast(connections.type.firstBase())
+                #connections = connections.cast(connections.type.firstBase())
                self.putSpecialValue('minimumitemcount', 0)
                self.putNumChild(1)
            if self.isExpanded():
@@ -3085,7 +3114,6 @@ class DumperBase:
            self.lalignment = None # Function returning alignment of this struct
            self.lbitsize = None
            self.lbitpos = None
-            self.lfirstBase = None
            self.ltarget = None # Inner type for arrays
            self.templateArguments = []
            self.code = None
@@ -3100,7 +3128,6 @@ class DumperBase:
            tdata.lalignment = self.lalignment
            tdata.lbitsize = self.lbitsize
            tdata.lbitpos = self.lbitpos
-            tdata.lfirstBase = self.lfirstBase
            tdata.ltarget = self.ltarget
            tdata.templateArguments = self.templateArguments
            tdata.code = self.code
@@ -3294,13 +3321,6 @@ class DumperBase:
                return tdata.lfields(value)
            return []

-        def firstBase(self):
-            #lfields = self.fields()
-            #if len(lfields) > 0 and lfields[0].isBaseClass:
-            #    return lfields[0].ltype
-            #return None
-            return self.typeData().lfirstBase
-
        def field(self, value, name, bitoffset = 0):
            #warn('GETTING FIELD %s FOR: %s' % (name, self.name))
            for f in self.fields(value):
@@ -420,10 +420,6 @@ class Dumper(DumperBase):
                tdata.code = TypeCodeComplex
            elif code in (lldb.eTypeClassClass, lldb.eTypeClassStruct, lldb.eTypeClassUnion):
                tdata.code = TypeCodeStruct
-                #if nativeType.GetNumberOfDirectBaseClasses() > 0:
-                #    firstBase = nativeType.GetDirectBaseClassAtIndex(0).GetType()
-                #    if firstBase.GetByteSize() >= 2 * self.ptrSize():
-                #        tdata.lfirstBase = self.fromNativeType(firstBase)
                tdata.lalignment = lambda : \
                    self.nativeStructAlignment(nativeType)
                tdata.lfields = lambda value : \