Re: cast in gdb python results in virtual baseclass botch

[Andrà PÃnitz <andre dot poenitz at nokia dot com>]

On Wednesday 13 April 2011 19:08:17 ext Christoph Mathys wrote:
> On Wed, Apr 13, 2011 at 5:26 PM, Andrà PÃnitz <andre.poenitz@nokia.com> wrote:
> > I don't think you have to cast.
> >
> > inner = item.value["px"].dereference()   has already the correct type.
> 
> I expressed myself badly:
> 
> class XmlNodeInterface
> { };
> class XmlNode : public XmlNodeInterface
> {
>  xmlNode* m_pNode;
> };
> 
> I've got a reference to a "shared_ptr<IXmlNode>", and I want m_pNode.
> So after I extracted px, I think I have to downcast from IXmlNode to XmlNode

Then

 item.value["px"].dereference().cast(gdb.lookup_type("IXmlNode").pointer())["m_pNode"]

or something similar might do the trick.

Regards,
Andre'


PS: In similar cases I use a 'lookupType' function defined as follows:

typeInfoCache = {}

def lookupType(typestring):
    type = typeCache.get(typestring)
    if type is None:
        ts = typestring
        while True:
            if ts.startswith("class "):
                ts = ts[6:]
            elif ts.startswith("struct "):
                ts = ts[7:]
            elif ts.startswith("const "):
                ts = ts[6:]
            elif ts.startswith("volatile "):
                ts = ts[9:]
            elif ts.startswith("enum "):
                ts = ts[5:]
            elif ts.endswith("const"):
                ts = ts[-5:]
            elif ts.endswith("volatile"):
                ts = ts[-8:]
            else:
                break
        try:
            type = gdb.lookup_type(ts)
        except RuntimeError, error:
            # See http://sourceware.org/bugzilla/show_bug.cgi?id=11912
            exp = "(class '%s'*)0" % ts
            try:
                type = parseAndEvaluate(exp).type.target()
            except:
                # Can throw "RuntimeError: No type named class Foo."
                pass
        except:
            pass
        typeCache[typestring] = type
    if type is None and typestring.endswith('*'):
        type = lookupType(typestring[0:-1])
        if not type is None:
            type = type.pointer()
            typeCache[typestring] = type
    if type is None:
        # could be gdb.lookup_type("char[3]") generating
        # "RuntimeError: No type named char[3]"
        pass
    return type