[cfe-commits] [Patch] Mark pass-by-reference as uninitialized variable use on initialization

[Richard Trieu]

On Mon, Aug 6, 2012 at 4:09 PM, Richard Smith <richard at metafoo.co.uk> wrote:

> On Mon, Aug 6, 2012 at 3:29 PM, Richard Trieu <rtrieu at google.com> wrote:
>
>> Modify the self-reference visitor to mark pass-by-reference to function
>> calls as uninitialized use.  This will warn on code such as:
>>
>> const string Foo = "prefix" + Foo + "suffix";
>>
>
> Can we put this under a more specific -W flag? -Wuninitialized is intended
> to be essentially free of false positives.
>
Would this be more suited for a different uninitialized group or a new flag
altogether?

>
> I'm a little concerned that this uninitialized-variables warning is
> deviating from the behavior of the CFG-based warning, which explicitly
> excludes variables passed by reference to functions from its list of uses,
> so if this is effective at finding bugs, perhaps we should add this check
> there too.
>
At least for classes, this seems to be a reasonable check.  I'm not sure if
it would be useful for other cases.

>
> --- lib/Sema/SemaDecl.cpp (revision 161345)
> +++ lib/Sema/SemaDecl.cpp (working copy)
> @@ -6223,7 +6223,7 @@
>
>      void VisitImplicitCastExpr(ImplicitCastExpr *E) {
>        if ((!isRecordType && E->getCastKind() == CK_LValueToRValue) ||
> -          (isRecordType && E->getCastKind() == CK_NoOp))
> +          (E->getCastKind() == CK_NoOp))
>
> Drop these parens... But I'm not really clear on what this is checking
> for. Presumably qualification conversions, but why are those a good place
> to look for self-initialization?
>
T -> const T conversion when passed by reference.
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