Fix warnings due to missing override specification

[gganis]

BEGINRELEASENOTES

• Fix warnings due to missing override specification

ENDRELEASENOTES

[tmadlener]

Are these the only places where this gets flagged? Naively I would expect there to be more, since we are probably implementing more virtual functions, but maybe I am thinking about test code(?).

[jmcarcell]

It's in a bunch of tests but also in places that are not tests:

k4FWCore/components/PodioOutput.h
22:  virtual StatusCode initialize();
25:  virtual StatusCode execute();
27:  virtual StatusCode finalize();

k4FWCore/components/PodioInput.h
26:  virtual StatusCode initialize();
28:  virtual StatusCode execute();
30:  virtual StatusCode finalize();

So it would be better if we can deal with this warning in all places at once. Is this a clang specific warning? I don't remember any warnings when compiling with gcc.

[tmadlener]

Both gcc and clang can warn about this, for clang its modernize-use-override for gcc it is suggest-override, but the defaults are probably different in both cases. Anyhow, e.g. for podio we have this enabled in the clang-tidy configuration.

[jmcarcell]

Ok so this is interesting and annoying at the same time: for gcc it's not enabled by default and also not included in -Wall nor -Wextra while for clang it is enabled by default. On top of that they may have different behaviour based on what this answer says: https://stackoverflow.com/a/41109550
(the warning in clang is -Winconsistent-missing-override and here it says it's on by default: https://clang.llvm.org/docs/DiagnosticsReference.html#winconsistent-missing-override)

[tmadlener]

I think only using either override or final and dropping virtual makes both compilers happy, at least it does for podio.

[jmcarcell]

Closing this one in favor of #143