[cfe-commits] [Patch] Warn about self-init of refs using parenthesized initializers

[Richard Trieu]

After talking with Richard Smith, I will be working on some changes to the
SelfReferenceVisitor.  The HandleExpr was a bit of a hack when first
introduced and should be removed.  The call to the self reference checker
should be moved later into the function so that the initial Expr will be
processed first (this processing will get rid of the ParenListExpr).  This
should clean up the visitor a bit.  Stay tuned for a patch.

On Fri, Sep 28, 2012 at 1:34 PM, Pan, Wei <wei.pan at intel.com> wrote:

>  I discovered this starting from the following example****
>
> ** **
>
> extern int &foo();****
>
> int &m([&]() { m = foo(); return m; }());****
>
> ** **
>
> This should be also warned too.****
>
> ** **
>
> *From:* cfe-commits-bounces at cs.uiuc.edu [mailto:
> cfe-commits-bounces at cs.uiuc.edu] *On Behalf Of *Richard Smith
> *Sent:* Friday, September 28, 2012 4:15 PM
> *To:* Jordan Rose; Richard Trieu
> *Cc:* llvm cfe
> *Subject:* Re: [cfe-commits] [Patch] Warn about self-init of refs using
> parenthesized initializers****
>
> ** **
>
> I don't think the patch is right. My recollection of this class is (though
> perhaps Richard Trieu can correct me):****
>
> ** **
>
> HandleExpr is intended to be called for the expression which is the
> top-level initializer of the declaration.****
>
> HandleValue is intended to be called for an expression which is "used"
> (either directly in the initialization of the result, or as the operand of
> an lvalue-to-rvalue conversion).****
>
> Visit* are called for all evaluated subexpressions (including ones we
> don't consider to be "used").****
>
> ** **
>
> So... I think that we shouldn't be calling HandleExpr (nor HandleValue)
> from VisitParenListExpr, since it doesn't imply a use, in the required
> sense. I think the right way to deal with this is to add special cases for
> ParenListExpr and InitListExpr to HandleExpr. We also need to decide
> whether to warn in these cases:****
>
> ** **
>
> int n(n); // Warn here, or is this treated like int n = n;?****
>
> int n{n}; // Warn here, or is this treated like int n = n;?****
>
> ** **
>
> ** **
>
> FWIW, it looks like we're missing an IgnoreParenCasts call from
> HandleExpr, and the IgnoreParenImpCasts call in HandleValue should be
> IgnoreParenCasts. We don't currently warn on cases like these, for instance:
> ****
>
> ** **
>
> int &r = static_cast<int&>(r);****
>
> ** **
>
> ... nor ...****
>
> ** **
>
> struct S {} s = static_cast<S&>(s);****
>
> ** **
>
> On Fri, Sep 28, 2012 at 9:18 AM, Jordan Rose <jordan_rose at apple.com>
> wrote:****
>
> This still doesn't handle C++11 initialization, does it?
>
> void g() {
>         int &a{a};
> }
>
> Jordan****
>
>
>
> On Sep 28, 2012, at 4:05 , Hans Wennborg <hans at chromium.org> wrote:
>
> > Hi,
> >
> > As pointed out in Wei's email [1], Clang currently fails to warn about
> > self-initialized references when using parenthesized initializers:
> >
> >  void f() {
> >    int &a(a);
> >  }
> >
> > The attached patch fixes this. Please take a look.
> >
> > Thanks,
> > Hans
> >
> > [1].
> http://lists.cs.uiuc.edu/pipermail/cfe-dev/2012-September/024582.html****
>
> >
> <ref_self_init_parenthesized_initializers.patch>_______________________________________________
> > cfe-commits mailing list
> > cfe-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
>
> _______________________________________________
> cfe-commits mailing list
> cfe-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits****
>
> ** **
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20120928/a39085eb/attachment.html>