[Interest] Bug in Qt 4.8's destruction of QWizard fields??
schumann at fnal.gov
Mon May 7 20:30:31 CEST 2012
I have an application that core dumps when a user goes back and forth
through its wizard such that some wizard fields that are initially
created are no longer needed. Qt does appear to detect a need to clean
up and calls the following routine in src/gui/dialogs/qwizard.cpp:
> void QWizardPrivate::_q_handleFieldObjectDestroyed(QObject *object)
This routine finds the field to be deleted and then executes the
following two lines:
> it = fields.erase(it);
where field is a reference to "*it" and "it" points to the field to be
destroyed. this->fieldIndexMap apparently is to contain a mapping from
a field name to to its index in this->fields. (I base this statement
on the source code for QWizard::field.) Therefore, these two lines
appear to leave this->fields and this->fieldIndexMap in an inconsistent
state. Specifically, because removing an entry from the map does not
also shift all the values in the map higher than the value removed down
So if we initially have the following mapping ...
"field0" -> 0,
"field1" -> 1, and
"field2" -> 2
with fields of size 3. After destruction of "field1" we have ...
"field0" -> 0, and
"field2" -> 2
with fields of size 2. Now attempts to look up "field2" using
QWizard::field will have an out of bounds error and core dump because an
attempt to access this->fields will be made. It should be accessing
this->fields, but does not because the mapping is no longer correct.
So that is my theory that there is in fact a bug in
QWizardPrivate::_q_handleFieldObjectDestroyed*. *Have I actually missed
something instead though? Other opinions and insights would be
appreciated please? Thanks in advance for any insights.
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