[LLVMdev] [RFC] C++11: 'virtual' and 'override'

[David Blaikie]

On Wed, Mar 5, 2014 at 1:10 AM, Chris Lattner <clattner at apple.com> wrote:
>
> On Mar 4, 2014, at 11:43 PM, Richard Smith <richard at metafoo.co.uk> wrote:
>
> On Tue, Mar 4, 2014 at 10:59 PM, Chris Lattner <clattner at apple.com> wrote:
>>
>> On Mar 4, 2014, at 10:48 PM, Duncan Exon Smith <dexonsmith at apple.com>
>> wrote:
>>
>>
>> Related, should we require use of 'override' when methods override a base
>> class method?
>>
>>
>> My vote: require override.
>>
>>
>> +1: override is useful and prevents errors.
>>
>> Would it be too much to have clang emit a warning/error if override is
>> missing?  I know that sounds crazy and people hate errors which fire too
>> often, but there's not too much C++11 code out there yet, and so we have a
>> chance to put errors/warnings in now without too much pain.  People might
>> just get used to them and think its how code has to be written :)
>>
>>
>> Might be a nightmare when including legacy headers, but warnings can
>> always be disabled...
>>
>>
>> A clang warning for this would be awesome, but it should be off by
>> default.  That said, the build of LLVM itself could detect that Clang had
>> this warning and turn it on.  I think it would be great to have the
>> makefiles/cmake detect modern clang's and turn on additional warnings that
>> we can't inflict on the world by default.
>
>
> It might be reasonable to warn if a class has both a function marked
> 'override' and a function that overrides but is not marked 'override'.
>
>
> That could be useful - because it means that the author of the class is at
> least thinking about override - but having a "coding style" warning of "I
> always intend to use override" would still be useful.

Doug (not sure about other Clang owners) is pretty hesitant about
implementing coding style warnings - anything with such a high false
positive rate as to be off by default is assumed to be a non-starter
in Clang (though perhaps things have changed in the years since I last
tested the waters here).

And now that we have something like clang-tidy, it's perhaps less of
an issue... we'll see.

- David