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From: =?utf-8?q?Andr=C3=A9_P=C3=B6nitz?= <andre.poenitz@nokia.com>
To: gdb@sourceware.org
Subject: Re: cast in gdb python results in virtual baseclass botch
Date: Wed, 13 Apr 2011 17:29:00 -0000
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On Wednesday 13 April 2011 19:08:17 ext Christoph Mathys wrote:
> On Wed, Apr 13, 2011 at 5:26 PM, Andr=C3=A9 P=C3=B6nitz <andre.poenitz@no=
kia.com> wrote:
> > I don't think you have to cast.
> >
> > inner =3D item.value["px"].dereference()   has already the correct type.
>=20
> I expressed myself badly:
>=20
> class XmlNodeInterface
> { };
> class XmlNode : public XmlNodeInterface
> {
>  xmlNode* m_pNode;
> };
>=20
> 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 XmlN=
ode

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 =3D {}

def lookupType(typestring):
    type =3D typeCache.get(typestring)
    if type is None:
        ts =3D typestring
        while True:
            if ts.startswith("class "):
                ts =3D ts[6:]
            elif ts.startswith("struct "):
                ts =3D ts[7:]
            elif ts.startswith("const "):
                ts =3D ts[6:]
            elif ts.startswith("volatile "):
                ts =3D ts[9:]
            elif ts.startswith("enum "):
                ts =3D ts[5:]
            elif ts.endswith("const"):
                ts =3D ts[-5:]
            elif ts.endswith("volatile"):
                ts =3D ts[-8:]
            else:
                break
        try:
            type =3D gdb.lookup_type(ts)
        except RuntimeError, error:
            # See http://sourceware.org/bugzilla/show_bug.cgi?id=3D11912
            exp =3D "(class '%s'*)0" % ts
            try:
                type =3D parseAndEvaluate(exp).type.target()
            except:
                # Can throw "RuntimeError: No type named class Foo."
                pass
        except:
            pass
        typeCache[typestring] =3D type
    if type is None and typestring.endswith('*'):
        type =3D lookupType(typestring[0:-1])
        if not type is None:
            type =3D type.pointer()
            typeCache[typestring] =3D type
    if type is None:
        # could be gdb.lookup_type("char[3]") generating
        # "RuntimeError: No type named char[3]"
        pass
    return type