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

[Richard Trieu]

Committed the fix at r164951

On Fri, Sep 28, 2012 at 7:46 PM, Richard Trieu <rtrieu at google.com> wrote:

> I have started a new thread with a patch for the self-init checker that
> will work better with references and CC-ed everyone here.
>
>
> On Fri, Sep 28, 2012 at 3:53 PM, Richard Trieu <rtrieu at google.com> wrote:
>
>> 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****
>>>
>>> ** **
>>>
>>
>>
>
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