[cfe-commits] [patch] Warn on self assignment for member variables

[Nico Weber]

New patch!

In this version:
* no longer uses FoldingSetNodeID, which hopefully addressed performance
concerns (this means "s->a_ = s->a_" is no longer caught, but that has
never happened to me anyway)
* ObjC support as requested by Jordan
* Fix to an existing ObjC test that triggered this warning (accidentally I
think)


On Mon, Jun 25, 2012 at 5:10 PM, Jordan Rose <jordan_rose at apple.com> wrote:

>
> On Jun 25, 2012, at 16:27 , Nico Weber <thakis at chromium.org> wrote:
>
> On Mon, Jun 25, 2012 at 3:49 PM, Jordan Rose <jordan_rose at apple.com>
> wrote:
>
>
> On Jun 25, 2012, at 14:43 , Nico Weber <thakis at chromium.org> wrote:
>
> Full build of the 'chrome' target with this warning on my MBP: real
> 31m41.500s
> Same clang binary at the same revision, without the warning: real
> 31m53.572s
>
> So the compile-time impact of the warning is below noise I'd say.
>
> Nico
>
>
> Did you remember to add a guard around the "work" part of
> CheckIdentityMemvarAssignment? Or were you still doing the work and just
> not emitting the warning?
>
>
> I uncommented the call to "CheckIdentityMemvarAssignment" (and clang
> warned me that the static function CheckIdentityMemvarAssignment
> wasn't used). With "same binary" I meant "built at the same revision"
>
>
> Okay, I see. I'm a little concerned along with Ted because copying over
> pieces of another struct does seem like something common enough to do, but
> I guess it's fine.
>
> This probably won't catch "this->_a = _a", but maybe that's okay. It is a
> typo you might make in a setter, though.
>
> BTW, this would be a good warning to have in Objective-C as well (
> ObjCIvarRefExpr). The equivalent example there would be "self->_a = _a".
>
> Thanks for working on this. I think over all it is a good warning to have.
>
> Jordan
>
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