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

[Duncan Exon Smith]

> On Mar 4, 2014, at 22:38, Pete Cooper <peter_cooper at apple.com> wrote:
> 
> 
>> On Mar 4, 2014, at 7:57 PM, Duncan P. N. Exon Smith <dexonsmith at apple.com> wrote:
>> 
>>> On 2014 Mar 4, at 15:01, Sean Silva <chisophugis at gmail.com> wrote:
>>> 
>>> On Mon, Mar 3, 2014 at 2:02 AM, David Blaikie <dblaikie at gmail.com> wrote:
>>>> On Sun, Mar 2, 2014 at 8:19 PM, Craig Topper <craig.topper at gmail.com> wrote:
>>>> While doing the conversion of LLVM_OVERRIDE to 'override' last night, I
>>>> noticed that the code base is rather inconsistent on whether the 'virtual'
>>>> keyword is also used when 'override' is used.
>>>> 
>>>> Should we have a coding standard for this? What's the preferred direction
>>>> here? Seems not having 'virtual' is less overall text, but not sure how
>>>> others feel.
>>> 
>>> My vote: omit virtual if override is used.
>> 
>> +1: virtual doesn’t add anything if override is present.
>> 
>>> (legitimate counterargument: harder to skim/match/read whether a
>>> function is virtual when it's not specified and "override" appears
>>> much later in the declaration)
>>> 
>>> One counter-datapoint: Personally, I have on at least one occasion caught myself not noticing a leading `virtual` and thinking that a method wasn't overriden because of the missing `override`. I guess the moral is that this can be pretty adaptable.
>>> 
>>> FWIW IMO the preferred end state is to have no useless leading `virtual`'s and using `override` for its intended purpose.
>>> 
>>> -- Sean Silva
>>> 
>>> 
>>>> 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...

>> 
>>>> I have clang-tidy checks for both though haven't implemented fixits for them
>>>> yet.
>>> 
>>> Cool. There has also been a suggestion that Clang could warn about
>>> omitted override if at least one other member function in the same
>>> class is marked override, which could get us a lot of value built into
>>> the compiler (but not 'all the way', so a clang-tidy check would still
>>> be appropriate).
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>> 
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>> 
>> 
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20140304/b89ec8b5/attachment.html>