Standardize usage of virtual/override/final in tools/gn/

Standardize usage of virtual/override/final in tools/gn/

The Google C++ style guide states:

  Explicitly annotate overrides of virtual functions or virtual
  destructors with an override or (less frequently) final specifier.
  Older (pre-C++11) code will use the virtual keyword as an inferior
  alternative annotation. For clarity, use exactly one of override,
  final, or virtual when declaring an override.

To better conform to these guidelines, the following constructs have
been rewritten:

- if a base class has a virtual destructor, then:
    virtual ~Foo();                   ->  ~Foo() override;
- virtual void Foo() override;        ->  void Foo() override;
- virtual void Foo() override final;  ->  void Foo() final;

This patch was automatically generated. The clang plugin can generate
fixit hints, which are suggested edits when it is 100% sure it knows how
to fix a problem. The hints from the clang plugin were applied to the
source tree using the tool in https://codereview.chromium.org/598073004.

BUG=417463
R=brettw@chromium.org

[brettw, 2014-10-21 21:03:27]

lgtm

[Peter Kasting, 2014-10-21 22:47:50]

pkasting@chromium.org changed reviewers:
+ pkasting@chromium.org

[Peter Kasting, 2014-10-21 22:47:51]

This seems to overlap with https://codereview.chromium.org/643063004/ .

The comment below is only from looking at one file, there may be others
affected.

https://codereview.chromium.org/667143003/diff/1/tools/gn/action_target_gener...
File tools/gn/action_target_generator.h (right):

https://codereview.chromium.org/667143003/diff/1/tools/gn/action_target_gener...
tools/gn/action_target_generator.h:19: virtual ~ActionTargetGenerator();
Shouldn't this be "override" instead of "virtual"?

[dcheng, 2014-10-21 22:57:15]

https://codereview.chromium.org/667143003/diff/1/tools/gn/action_target_gener...
File tools/gn/action_target_generator.h (right):

https://codereview.chromium.org/667143003/diff/1/tools/gn/action_target_gener...
tools/gn/action_target_generator.h:19: virtual ~ActionTargetGenerator();
On 2014/10/21 22:47:51, Peter Kasting wrote:
> Shouldn't this be "override" instead of "virtual"?

Yeah. I'm not sure why, but the plugin is currently missing some cases. =/

I'm going to be investigating this--I'm guessing one of the early returns is
somehow getting triggered, but I'm not yet sure how.

[viettrungluu, 2014-10-22 00:42:13]

viettrungluu@chromium.org changed reviewers:
+ viettrungluu@chromium.org

[viettrungluu, 2014-10-22 00:42:14]

https://codereview.chromium.org/667143003/diff/1/tools/gn/action_target_gener...
File tools/gn/action_target_generator.h (right):

https://codereview.chromium.org/667143003/diff/1/tools/gn/action_target_gener...
tools/gn/action_target_generator.h:19: virtual ~ActionTargetGenerator();
On 2014/10/21 22:57:15, dcheng wrote:
> On 2014/10/21 22:47:51, Peter Kasting wrote:
> > Shouldn't this be "override" instead of "virtual"?
> 
> Yeah. I'm not sure why, but the plugin is currently missing some cases. =/
> 
> I'm going to be investigating this--I'm guessing one of the early returns is
> somehow getting triggered, but I'm not yet sure how.

It's not missing it: the base class's dtor isn't virtual, so this is really a
bug in the code.

(Quite possibly, we should have a warning/error when a subclass has a virtual
dtor but the superclass doesn't.[*])

[*] At least when the superclass has an explicitly-declared dtor. Sometimes we
declare interfaces without providing dtors, which is somewhat debatable.[**]

[**] Arguably, in such cases, the interface should have a protected, but
possibly non-virtual dtor.

[dcheng, 2014-10-22 00:47:10]

On 2014/10/22 at 00:42:14, viettrungluu wrote:
>
https://codereview.chromium.org/667143003/diff/1/tools/gn/action_target_gener...
> File tools/gn/action_target_generator.h (right):
> 
>
https://codereview.chromium.org/667143003/diff/1/tools/gn/action_target_gener...
> tools/gn/action_target_generator.h:19: virtual ~ActionTargetGenerator();
> On 2014/10/21 22:57:15, dcheng wrote:
> > On 2014/10/21 22:47:51, Peter Kasting wrote:
> > > Shouldn't this be "override" instead of "virtual"?
> > 
> > Yeah. I'm not sure why, but the plugin is currently missing some cases. =/
> > 
> > I'm going to be investigating this--I'm guessing one of the early returns is
> > somehow getting triggered, but I'm not yet sure how.
> 
> It's not missing it: the base class's dtor isn't virtual, so this is really a
bug in the code.
> 
> (Quite possibly, we should have a warning/error when a subclass has a virtual
dtor but the superclass doesn't.[*])
> 
> [*] At least when the superclass has an explicitly-declared dtor. Sometimes we
declare interfaces without providing dtors, which is somewhat debatable.[**]
> 
> [**] Arguably, in such cases, the interface should have a protected, but
possibly non-virtual dtor.

I think you're right in this instance, but
https://codereview.chromium.org/665323004 also had some instances where it
appears the plugin missed stuff.

(Also I don't plan on committing this patch. Given the size of the original
patch, I didn't want to bother with fixing up OVERRIDE/FINAL, while it looks
like your patch updates them as well.)