Thanks!


I am not familiar with valgrind, but I suppose I could learn, if

there is still interest in a test case that triggers it.

--paulr



________________________________
From: [email protected] [[email protected]] on behalf of Richard Smith 
[[email protected]]
Sent: Wednesday, July 18, 2012 4:54 PM
To: Robinson, Paul
Cc: [email protected]
Subject: Re: [cfe-commits] [PATCH] Fix random crasher

On Wed, Jul 18, 2012 at 4:51 PM, Richard Smith 
<[email protected]<mailto:[email protected]>> wrote:
On Wed, Jul 18, 2012 at 3:55 PM, Robinson, Paul 
<[email protected]<mailto:[email protected]>> wrote:
Guard use of a possibly uninitialized field.

This was causing very unpredictable compiler crashes. I have not
provided a test because even our most reliable reproducer still failed
less than 10% of the time.

I really really really don't like sometimes-uninitialized fields
guarded by flags. It is not a robust practice and took us a couple of
weeks of poking at it to find the root cause. But it is how the rest
of SemaOverload handles this field, so we fixed it using the
prevailing practice in the module.

Do you know where the uninitialized OverloadCandidate is coming from? The only 
place I can see one being created is in OverloadCandidateSet::addCandidate, 
which says:

      Candidates.push_back(OverloadCandidate());

This zero-initializes the OverloadCandidate object.

I've checked in a variant on your change in r160470: it seems correct and 
appropriate even if FailureKind is always initialized, since we were previously 
implicitly and accidentally relying on ovl_fail_bad_deduction being nonzero.
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