[umbrello-devel] [umbrello] [Bug 351103] Umbrello crashes when changing type for an operation for a class

[Oliver Kellogg]

https://bugs.kde.org/show_bug.cgi?id=351103

Oliver Kellogg <okellogg at users.sourceforge.net> changed:

           What    |Removed                     |Added
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                 CC|                            |okellogg at users.sourceforge.
                   |                            |net

--- Comment #7 from Oliver Kellogg <okellogg at users.sourceforge.net> ---
(In reply to Challistobugs from comment #2)
> [...]
> I was changing the return type of an operation in a class.

Hmm let's see...

CodeMethodBlock inherits from OwnedCodeBlock,
    class CodeMethodBlock : public OwnedCodeBlock, [...]
and declares
    public slots:
        virtual void syncToParent();
However, the actual "connect" of this syncToParent() is not done in
CodeMethodBlock but rather in the parent class OwnedCodeBlock,
    void OwnedCodeBlock::initFields(UMLObject * parent)
    {
        [...]
        connect(m_parentObject, SIGNAL(modified()), this,
SLOT(syncToParent()));
    }
The problem is that OwnedCodeBlock::initFields() is called from within the
OwnedCodeBlock constructor,
    OwnedCodeBlock::OwnedCodeBlock (UMLObject * parent)
        : QObject (parent)
    {
        setObjectName(QLatin1String("anOwnedCodeBlock"));
        initFields(parent);
    }
which itself is called by the CodeMethodBlock constructor,
    CodeMethodBlock::CodeMethodBlock(ClassifierCodeDocument * doc, UMLObject *
parentObj,
                                            const QString & body, const QString
& comment)
      : OwnedCodeBlock (parentObj), [...]
which means that the connect() is done on a CodeMethodBlock object which itself
is not yet fully constructed: vtbl_ptr not yet initialized, dynamic method
dispatch to child class not possible.
By the way, the new code generators had this design error all over the place.
Years ago, I tried to fix the many occurrences of this pattern but gave up at
some point.

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