[cfe-commits] [PATCH] PR13824 warn if reinterpret_cast used for up/downcast

[Jordan Rose]

On Jan 22, 2013, at 16:08 , John McCall <rjmccall at apple.com> wrote:

> On Jan 22, 2013, at 2:58 PM, Alexander Zinenko <ftynse at gmail.com> wrote:
>> The attached patch addresses http://llvm.org/bugs/show_bug.cgi?id=13824. It emits a warning if reinterpret_cast is actually used to perform an upcast or a downcast which might lead to segfault in some cases.
> 
> In most cases, this is actually safe, and I don't feel comfortable saying it's unreasonable for code to rely on that.  This warning should only fire when the base subobject is in a virtual base or at a nonzero static offset.
> 
> You can use a CXXBasePaths object with Sema::IsDerivedFrom in order to determine the subobject access path.

I think I would still have a warning, since reinterpret_cast is harder to check statically and therefore is less future-proof. But I could see that warning being controlled by a separate flag.

Jordan

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