[PATCH] Fix generating TypeSourceInfo for invalid array type

[Richard Smith]

Thanks for the further investigation and testing! Could you recursively
create a trivial TypeSourceInfo for the TypeOfTypeLoc case?
On 6 Aug 2014 12:47, "Olivier Goffart" <ogoffart at woboq.com> wrote:

> On Wednesday 06 August 2014 09:10:35 Olivier Goffart wrote:
> > On Tuesday 05 August 2014 19:48:00 Richard Smith wrote:
> > > On Tue, Aug 5, 2014 at 3:16 PM, Olivier Goffart <ogoffart at woboq.com>
> wrote:
> > > > Hi,
> > > >
> > > > This fixes a crash in the RecursiveASTVisitor on such code:
> > > >  __typeof__(struct F*) var[invalid];
> > > >
> > > > The main problem is that when the type is invalid, we don't even
> > > > try to generate TypeSourceInfo for it, which lead to a crash when we
> try
> > > > to visit them in the tools.
> > > > This is solved in SemaType.cpp by actually generating the
> TypeSourceInfo
> > > > even for invalid types.
> > >
> > > I'm surprised by this: the code used to call getTrivialTypeSourceInfo
> in
> > > this case, which does create a TypeSourceInfo object. How do we end up
> > > with
> > > the TSI being null?
> >
> > the TSI is not null. It is somehow corrupted.
> > Valgrind trace show that the RecursiveASTVisitor tries to access
> > uninitialized memory on this line:
> > TRY_TO(TraverseTypeLoc(TL.getUnderlyingTInfo()->getTypeLoc()))
> >
> > And actually I realize now that the problem is something else:
> > ASTContext::getTrivialTypeSourceInfo  calls
> TypeOfTypeloc::initializeLocal
> > but there is no initializeLocal in TypeOfTypeLoc,  only in the base class
> > TypeofLikeTypeLoc,  which does not intitialize
> > TypeOfTypeLocInfo::UnderlyingTInfo,  hence the access to uninitialized
> > memory in the ASTVisitor and then the crash.
> > So this probably should be fixed as well for the other uses of
> > getTrivialTypeSourceInfo.
> >
> > But getTrivialTypeSourceInfo still looses all the source locations of all
> > the sub types, and I feel they should be kept even for invalid types in
> > order to be highlighted properly in IDEs
> >
> > > > The second problem is that if there is an error parsing the size of
> the
> > > > array, we bail out without actually registering that it should have
> been
> > > > an
> > > > array. Fix that Parser::ParseBracketDeclarator.
> > > > Move the check for invalid type a bit up in
> Sema::ActOnUninitializedDecl
> > > > in order to avoid unnecessary diagnostic
> > >
> > > This part looks fine. Is it possible to add a testcase for the improved
> > > recovery here, without the rest of the patch?
>
>
> Hi,
>
> I tested my patch on a larger codebase and had some different crashes on
> invalid code. So the original patch is not good.
>
> I also tried to initialize getLocalData()->UnderlyingTInfo to nullptr in a
> new
> TypeOfTypeLoc::initializeLocal function.  But this is not enough to slove
> the
> problem as the code in RecursiveASTVisitor assume it is not null (so i
> guess
> some other places might assume it not null?)
>
> I attached a safest patch which do not try to generate the typeloc for the
> invalid type, but at least fixes the crash in that case.
> But I noticed that other type might have the same problem
>
>
> --
> Olivier
>
>
>
>
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