CXX11 patch to warn if 'override' is missing on overriding virtual function

[jahanian]

On Sep 30, 2014, at 2:45 PM, Reid Kleckner <rnk at google.com> wrote:

> +def CXX11WarnOverrideMethod : DiagGroup<"warn-missing-override-on-overriding-method">;
> 
> Anyone care to bikeshed the name a bit? This flag feels really verbose, especially given that it gets a -W prefix.
> 
> Can we go with -Wmissing-override or -Winconsistent-missing-override to reflect the fact that it's heuristically triggered based on use of C++11 override somewhere in the class hierarchy?

I selected your suggestion of -Winconsistent-missing-override. I think I have covered everything else and
Doug responded to some of your comments let me know if I missed anything.

In r218925.
- Fariborz

> 
> On Fri, Sep 26, 2014 at 4:15 PM, jahanian <fjahanian at apple.com> wrote:
> 
> On Sep 26, 2014, at 4:12 PM, Douglas Gregor <dgregor at apple.com> wrote:
> 
>> LGTM
>> 
> Thanks. I want to add FixIts before checking it in.
> 
> - Fariborz
> 
>>> On Sep 26, 2014, at 4:10 PM, jahanian <fjahanian at apple.com> wrote:
>>> 
>>> 
>>> On Sep 26, 2014, at 3:37 PM, Douglas Gregor <dgregor at apple.com> wrote:
>>> 
>>>> 
>>>>> On Sep 26, 2014, at 3:03 PM, jahanian <fjahanian at apple.com> wrote:
>>>>> 
>>>>> 
>>>>> On Sep 25, 2014, at 11:51 AM, Argyrios Kyrtzidis <kyrtzidis at apple.com> wrote:
>>>>> 
>>>>>> 
>>>>>>> On Sep 25, 2014, at 11:24 AM, Douglas Gregor <dgregor at apple.com> wrote:
>>>>>>> 
>>>>>>>  I’d feel a lot better if some part of the warning could be on by default. For example, if you’ve uttered “override” at least once in a class, it makes sense to warn-by-default about any other overrides in that class that weren’t marked as “override”, because you’re being locally inconsistent. Or maybe you can expand that heuristic out to a file-level granularity (which matches better for the null point constant warning) and still be on-by-default.
>>>>>> 
>>>>>> This seems like a great idea to me!
>>>>>> For the 'override' I much prefer if it is class specific to make it less of a burden as an “always on” warning. We could have the checking done at the end of the class definition.
>>>>>> 
>>>>> 
>>>>> Here is the patch. Warning is on by default. Number of new warnings on clang tests is greatly reduced but there are still some.
>>>> 
>>>> +def warn_function_marked_not_override_overriding : Warning <
>>>> +  "%0 is not marked 'override' but overrides a member functions">,
>>>> +  InGroup<CXX11WarnOverrideMethod>;
>>>> 
>>>> “a member functions” shouldn’t be plural. Also, perhaps we should turn this around:
>>>> 
>>>> 	“%0 overrides a member function but is not marked ‘override’”
>>>> 
>>>> because that puts the context of the problem before the problem.
>>>> 
>>>> +  if (HasMethodWithOverrideControl) {
>>>> +    // At list one method has the 'override' control declared.
>>>> +    // Diagnose all other overridden methods which do not have 'override' specified on them.
>>>> +    for (auto *M : Record->methods())
>>>> 
>>>> “At list” -> “At least”.
>>>> 
>>>> Also, this means we’ll be taking two passes over the methods if any “override” is present, even though we won’t often warn here. How about extending this:
>>>> 
>>>> +      if (M->hasAttr<OverrideAttr>())
>>>> +        HasMethodWithOverrideControl = true;
>>>> 
>>>> with
>>>> 
>>>> 	else if (M->begin_overridden_methods() != M->end_overridden_methods())
>>>> 	  HasOverridingMethodWithoutOverrideControl = true;
>>>> 
>>>> and we only do this second pass when we know we’re going to warn, e.g., if HasMethodWithOverrideControl && HasOverridingMethodWithoutOverrideControl?
>>> 
>>> Thanks for quick review. Here is the updated patch.
>>> 	
>>> <override-patch.txt>
>>> 
>>> - Fariborz
>>>> 
>>>> 	- Doug
>> 
> 
> 
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