[Qt-interest] Replace Qt Allocator

[Eric Clark]

Yes and no. I am good with templates, but not as good as many of the guys at trolltech/nokia. I have much confidence in myself most of the time when it comes to C++, but unfortunately I would not know where to begin here. However, I do know that if I add a global new and delete to the qglobal header file and make new call qMalloc() and delete call qFree(), and then replace the calls in qFree() and qMalloc() to call nedfree() and nedmalloc() respectively, everything works just fine.

Eric

> -----Original Message-----
> From: qt-interest-bounces at trolltech.com [mailto:qt-interest-
> bounces at trolltech.com] On Behalf Of Scott Aron Bloom
> Sent: Wednesday, September 16, 2009 3:47 PM
> To: qt-interest at trolltech.com
> Subject: Re: [Qt-interest] Replace Qt Allocator
> 
> Have you considered patching QList yourself?
> 
> 
> 
> -----Original Message-----
> From: qt-interest-bounces at trolltech.com
> [mailto:qt-interest-bounces at trolltech.com] On Behalf Of Eric Clark
> Sent: Wednesday, September 16, 2009 1:43 PM
> To: Qt Interest (qt-interest at trolltech.com)
> Subject: Re: [Qt-interest] Replace Qt Allocator
> 
> 
> 
> > -----Original Message-----
> > From: qt-interest-bounces at trolltech.com [mailto:qt-interest-
> > bounces at trolltech.com] On Behalf Of RZ
> > Sent: Wednesday, September 16, 2009 1:55 PM
> > To: qt-interest at trolltech.com
> > Subject: Re: [Qt-interest] Replace Qt Allocator
> >
> > Hi,
> >
> > don't know if that helps - but we use TLSF (which is not so much
> faster
> > AFAIK but maybe we have slightly different use cases).
> >
> > We also had problems with "strange" crashes - until a colleague found
> > out that we had to use a compiler switch (for thread enabling within
> > TLSF).
> >
> > hmm, maybe there's something like this....
> 
> 
> Actually, there is, but we have already done that. We know with 100%
> assurance that the problem is in Qt with the constructor and destructor
> of the QList.
> 
> Thank You though!
> 
> >
> > RZ
> >
> > > Hello All,
> > >
> > >
> > >
> > > Our program uses a system allocator called nedmalloc. We override
> the
> > > new and delete operators to use this system allocator. However,
> after
> > > porting to Qt 4 we have ran into some issues with the QList class
> and
> > > it's destructor. When the list is destructed, it attempts to free
> the
> > > memory created by the list, but nedfree() crashes because the
> memory
> > was
> > > instantiated using the system allocator, malloc(). Here is the
> > problem:
> > >
> > >
> > >
> > > The problem is indeed a violation of the ODR requirement in the ISO
> > C++
> > > spec. For example in this line:
> > >
> > >
> > >
> > >    QModelIndexList indexes = list->selectionModel()-
> >selectedRows();
> > >
> > >
> > >
> > > QModelIndexList exists in the local binary due to being a templated
> > type
> > > based on QList, therefore its destructor is called from the local
> > binary
> > > where ::operator delete has been defined to invoke nedmalloc.
> > > Unfortunately the initial constructor of the list (selectedRows())
> > > exists in one of the Qt DLL binaries where ::operator new is
> defined
> > to
> > > invoke the system allocator.. Therefore the list is being
> constructed
> > > with the system allocator and destructed with nedmalloc - this
> > obviously
> > > enough provokes a segfault as ODR is violated.
> > >
> > >
> > >
> > > I was told by some guys on this interest board that I should build
> > > nedmalloc into Qt. However, after doing so, I still get the same
> > error.
> > > What I did to build nedmalloc into Qt, was I modified the body of
> > > qFree(), qMalloc(), and qRealloc() to use nedfree(), nedmalloc(),
> and
> > > nedRealloc() respectively. This apparently was not enough to fix
> the
> > > problem. Could anyone tell me what else needs to be done? Do I need
> > to
> > > override the new and delete operators in Qt as well? Are there any
> > > direct calls to malloc() in the code that I am unaware of?
> > >
> > >
> > >
> > > Any help with this would be greatly appreciated!
> > >
> > >
> > >
> > > Eric
> > >
> > >
> > >
> > _______________________________________________
> > Qt-interest mailing list
> > Qt-interest at trolltech.com
> > http://lists.trolltech.com/mailman/listinfo/qt-interest
> 
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