On 3 Jan 2016, at 8:43 PM, Markus Mohrhard <markus.mohrh...@googlemail.com> wrote: > > Hey > > On Sun, Jan 3, 2016 at 9:20 AM, Chris Sherlock <chris.sherloc...@gmail.com> > wrote: > Hi all, > > I’ve been getting an OSL_ENSURE failure when I run LibreOffice on my Ubuntu > Linux VM. > > The error is: > > warn:legacy.osl:25546:1:sw/source/core/attr/format.cxx:227: > SwFormat::~SwFormat: Def dependents! > > This appears to be occuring because the OSL_ENSURE is calling on > DerivedFrom(), which actually returns the following: > > return const_cast<SwFormat*>(static_cast<const SwFormat*>(GetRegisteredIn())); > > GetRegisteredIn() is just an event source of type SwModify, the odd thing is > that it calls on GetRegistedIn() which is NOT a member of SwModify (or any > child classes). > >> In fact, I’m surprised that this even compiles, as I was under the >> impression that a static_cast was a compile time check... >> >> I can only help you with the C++ part but not explain why it makes sense to >> call that code. >> >> The code calls SwFormat::GetRegisteredIn which is actually >> SwClient::GetRegisteredIn (through the inheritance hierarchy >> SwFormat->SwModify->SwClient). SwClient::GetRegisteredIn returns a pointer >> to a SwModify where the code actually assumes that it always returns a >> SwFormat.
Ah - I appear to have misread the inheritance on that class. Thanks :-) > http://opengrok.libreoffice.org/xref/core/sw/inc/format.hxx#110 > > Anyway, what *exactly* is this attempting to do? The name looks like it’s > doing a debugging check to ensure that the SwFormat class was registered in a > derived class, but I can’t see how this would ever work! > > >> It looks a bit like it is using some generic writer code to store the >> inheritance of the styles. > > > In fact, wouldn’t a dynamic_cast be better, as this most specifically down or > upcasts a pointer, and returns NULL if it fails? > >> That depends on all the code around it. Here the code just assumes that all >> returned SwModify objects are actually SwFormat objects. I did some more reading of static_cast - my understanding is that static_cast will up-cast or down-cast the object without any runtime safety checks. What isn’t clear is what happens when you try to do a static_cast on two entirely unrelated classes. Would DerivedFrom() work by just doing a static_cast? Regardless, the OSL_ENSURE is expecting a true, but is getting a false so the original writers of the code think that something is going wrong - I suppose that ultimately it matters more whether there is an issue in the check, or literally something is going badly wrong in the code and the object is *not* derived correctly and there’s a bug there somewhere… Sorry, not experienced at all in this module, and casting in c++ with the different static, dynamic and reinterpret casts has always been a bit tricky for me (well, not so much now that I’ve had a good read). If these questions are a bit obvious, please let me know and I’ll code up some scenarios to get a better understanding of how casting objects in C++ works (in fact, I’ll probably do this anyway, I’m knee-deep in refactoring VCL code). Chris > > Any advise on this would be greatly appreciated, got me thoroughly tricked... > > Chris > > _______________________________________________ > LibreOffice mailing list > LibreOffice@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/libreoffice _______________________________________________ LibreOffice mailing list LibreOffice@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/libreoffice
