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

[jahanian]

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.
	

- Fariborz
> 
> 	- Doug
> 
> 

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