r175425 - Disable dead stores checker for template instantations. Fixes <rdar://problem/13213575>.

[Ted Kremenek]

On Feb 17, 2013, at 11:25 PM, David Blaikie <dblaikie at gmail.com> wrote:

> On Sun, Feb 17, 2013 at 11:18 PM, Ted Kremenek <kremenek at apple.com> wrote:
> Author: kremenek
> Date: Mon Feb 18 01:18:28 2013
> New Revision: 175425
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=175425&view=rev
> Log:
> Disable dead stores checker for template instantations.  Fixes <rdar://problem/13213575>.
> 
> Modified:
>     cfe/trunk/lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp
>     cfe/trunk/test/Analysis/dead-stores.cpp
> 
> Modified: cfe/trunk/lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp?rev=175425&r1=175424&r2=175425&view=diff
> ==============================================================================
> --- cfe/trunk/lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp (original)
> +++ cfe/trunk/lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp Mon Feb 18 01:18:28 2013
> @@ -419,6 +419,15 @@ class DeadStoresChecker : public Checker
>  public:
>    void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
>                          BugReporter &BR) const {
> +
> +    // Don't do anything for template instantiations.
> +    // Proving that code in a template instantiation is "dead"
> +    // means proving that it is dead in all instantiations.
> +    // This same problem exists with -Wunreachable-code.
> 
> I believe last time we spoke about this we agreed that correctness can be attained by examining template patterns not specializations for unreachable code. Your concern was one of performance that I never did get around to providing numbers for (your concern was that examining all template patterns might be too expensive) - I'm not sure if you have the same concern for the Static Analyzer in this regard, or an easier way to verify the perf impact to thins you care about here.
> 
> (or perhaps the Static Analyzer already gets this right by examining template patterns elsewhere?)
>  

Hi David,

You are correct.  While it is true the analyzer has more "CPU time to burn" than a compiler warning, here was my thinking:

(1) This warning should possibly be made one day into a compiler warning, where the same performance requirements for -Wunreachable-code apply.  Thus until we feel comfortable with the solution we devised for -Wunreachable-code, it seems reasonable to wait on applying the same solution here.

(2) This was designed to be an expedient solution, addressing a clear case of reducing false positives.  This code has not been tested at all on analyzing template patterns, which was beyond the time I had to work on this right now.

I still agree with you, however, that looking at template patterns may be the best long-term solution, but there are many details left to be figured out there.

Cheers,
Ted

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20130217/bf12aed4/attachment.html>