[cfe-commits] [PATCH] Fix uninitialized variable tracking for compound assignments

[Ted Kremenek]

On Jul 16, 2012, at 1:06 PM, Richard Smith <richard at metafoo.co.uk> wrote:

> On Mon, Jul 16, 2012 at 12:55 PM, Ted Kremenek <kremenek at apple.com> wrote:
> 
> On Jul 15, 2012, at 10:14 PM, Richard Smith <richard at metafoo.co.uk> wrote:
> 
>> The patch replaces the 'track the last DeclRefExpr we saw' technique with a separate pass to classify the DeclRefExprs as use or initialization. Fixing this exposed some "false" positives on some benchmarking code which looks like:
>> 
>> void f() {
>>   volatile int n;
>>   for (int i = 0; i < N; ++i)
>>     n += f();
>> }
>> 
>> ... so the patch classifies compound-assignments as neither initialization nor use (it leaves the variable uninitialized if it was before, and leaves it initialized if it was before).
>> 
> 
> Hi Richard,
> 
> One comment on this last point.  We tend to like avoiding the uninitialized value taint propagating after the first use to avoid a cascade of warnings.  Your last comment here implies that were we to flag a warning at "n += f()" we might also flag another warning later if 'n' is used again.  Is that true?
> 
> -Wuninitialized only produces one warning per variable. That's handled in the Sema layer; the Analysis layer reports all uninitialized uses. My patch doesn't change that side of things.

Right, makes sense.  Overall, this patch looks good to me, and is a nice cleanup.
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