[PATCH] D12301: [PATCH] New checker for UB in handler of a function-try-block

[Richard Smith via cfe-commits]

On Mon, Aug 24, 2015 at 3:36 PM, Aaron Ballman <aaron.ballman at gmail.com>
wrote:

> On Mon, Aug 24, 2015 at 6:29 PM, Richard Smith <richard at metafoo.co.uk>
> wrote:
> > On Mon, Aug 24, 2015 at 3:23 PM, Aaron Ballman <aaron.ballman at gmail.com>
> > wrote:
> >>
> >> aaron.ballman created this revision.
> >> aaron.ballman added reviewers: alexfh, rsmith.
> >> aaron.ballman added a subscriber: cfe-commits.
> >>
> >> Per [except.handle]p10, the handler for a constructor or destructor
> >> function-try-block cannot refer to a non-static member of the object
> under
> >> construction. This patch adds a new clang-tidy check that warns the user
> >> when they've hit this undefined behavior.
> >>
> >> Due to how infrequent function-try-blocks appear on constructors and
> >> destructors in the wild compared to how often member expressions are
> >> encountered, I felt this was more appropriate as a clang-tidy check
> than as
> >> a semantic warning. I was concerned with efficiency of checking whether
> an
> >> arbitrary member expression was referring to the object under
> >> construction/destruction within the function-try-block catch handler
> scope.
> >
> >
> > Seems like this would be very cheap to check in the case where the object
> > expression is an implicit or explicit CXXThisExpr. It'd be good to have a
> > frontend warning for that case.
>
> Are you thinking the check would likely in BuildMemberReferenceExpr()
> and I would just have to look at the current scope to determine
> whether it's a function-try-block catch handler?


Yes, somewhere around there. You might need to wire a Scope* though a
couple of layers though.


> When I looked into
> doing a frontend warning for this, I seemed to struggle with figuring
> out specifically that I was in the catch handler of a
> function-try-block of a constructor or destructor.


Looks like there's no better method than walking up the Scope stack until
you hit a scope with the FnTryCatchScope flag (or leave the function),
currently.
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