[llvm-dev] [GSoC 2016] Capture Tracking - False Positives

[Scott Egerton via llvm-dev]

Anna,

Thank you for this, I've been giving this a look over and will continue
to do so.

Many thanks,
Scott

On Thu, 2016-06-09 at 19:32 +0000, Anna Thomas wrote:
> Scott,
> 
> I think trying to get the list of *all* possible false positives in
> the capture tracking analysis will be a hard problem. Perhaps start
> with a couple and go through the implementation process.
> 
> You could start with trying to see which optimizations use the
> capture tracking calls PointerMayBeCaptured and
> PointerMayBeCapturedBefore (the flow insensitive version is used more
> often). 
> 
> Then instrument the PointerMayBeCaptured code for the cases they
> return true. Run small/large code through these optimizations which
> call capture tracking and see if what’s returned as captured is
> actually captured. 
> This would give you some ideas on what’s being marked as captured,
> and a more concrete meaning for captured. 
> 
> You can also query through phabricator to get a sense of existing
> false positives in capture tracking that have already been found and
> fixed. Example:
> http://reviews.llvm.org/rL89421
> 
> 
> Hope this helps.
> Anna 
> 
> > On Jun 9, 2016, at 1:11 PM, Scott Egerton <scott.egerton1 at gmail.com
> > > wrote:
> > 
> > Hello Anna,
> > 
> > I've been looking into compiling a list of all of the false
> > positives
> > in the current Capture Tracking Analysis, but I'm having a bit of
> > trouble getting my head around it all. I feel like I understand it
> > at a
> > theoretical level but jumping into the implementation is quite
> > daunting.
> > 
> > I would appreciate any advice you could give to point me in the
> > right
> > direction.
> > 
> > Many thanks,
> > Scott
>