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

[Alexander Zinenko]

Hello!

If this patch is good enough, could someone commit it, please?


On 24 January 2013 21:55, Alexander Zinenko <ftynse at gmail.com> wrote:

> On 24 January 2013 04:33, Jordan Rose <jordan_rose at apple.com> wrote:
>
>>
>> On Jan 23, 2013, at 14:53 , Dmitri Gribenko <gribozavr at gmail.com> wrote:
>>
>> > On Thu, Jan 24, 2013 at 12:40 AM, Alexander Zinenko <ftynse at gmail.com>
>> wrote:
>> >> On 23 January 2013 23:52, Dmitri Gribenko <gribozavr at gmail.com> wrote:
>> >>> I think it is sensible to leave the warning on by default.  The
>> >>> purpose of a separate flag is to turn off the (possibly) noisy case
>> >>> separately.
>> >>
>> >> Having it on by default, clang fails to pass these tests:
>> >>    Clang :: Analysis/inlining/dyn-dispatch-bifurcate.cpp
>> >>    Clang :: SemaCXX/address-space-conversion.cpp
>> >> That's why the noisy version was disabled by default even in the first
>> >> version.
>> >
>> > Well, compiler tests do weird things, so this is not representative.
>>
>> dyn-dispatch-bifurcate is actually what encouraged me to file that PR in
>> the first place. You can go ahead and add it as an expected warning there.
>
>
>> For address-space-conversion, you could disable the warning in the RUN
>> line.
>>
>
> Thanks, I was not sure changing anyone else's test is OK.  Updated patch
> modifies these tests.
>
> On Jan 23, 2013, at 14:53 , Dmitri Gribenko <gribozavr at gmail.com> wrote:
>
>> > I think the only reasonable false positive source for zero adjustment
>> > case is templates:
>> >
>> > template<typename T, typename U>
>> > void foo(T *t) {
>> >  ... reinterpret_cast<U*>(t);
>> > }
>> >
>> > Where T and U have some subtyping relationship.
>>
>
> Warning could be disabled for dependent types.
> Trivial case warning adds an extra note where the template was
> instantiated, though. As for me it's worth still having it enabled.
>
> template.cpp:15:10: warning: 'reinterpret_cast' is used as an upcast from
> type 'B *' to its base type 'A *' [-Wreinterpret-updown-zero-adjustment]
>   (void)*reinterpret_cast<U *>(t);
>          ^~~~~~~~~~~~~~~~~~~~~~~~
> template.cpp:20:3: note: in instantiation of function template
> specialization 'foo<B, A>' requested here
>   foo<B, A>(&b);
>
>
>
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