Fix clang warning about unused function

[uklotzde]

No description provided.

[Holzhaus]

This applies to the whole file. Can we just do it for the single function?

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-function"
// Code that throws warning goes here
#pragma clang diagnostic pop

Also, please add a comment why this is necessary.

[Holzhaus]

Another thing: It this warning legit? If so, I assume that GCC doesn't throw the warning because it's buggy. If that's the case, it might get fixed in later versions of GCC. Hence, we could use this instead:

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
// Code that throws warning goes here
#pragma GCC diagnostic pop

Apparently clang understands GCC pragmas, but not vice versa.

[uklotzde]

I don't want to complicate the code unless actually needed. This could happen whenever using Q_DECLARE_OPERATORS_FOR_FLAGS, which defines functions that might never be used.

[uklotzde]

I could close this PR, but then the builds will fail with Clang 10.x once it becomes available. I only used it for a test build.

[daschuer]

A unused function is not a problem on its own.
This might become a problem if another unexpected function is used instead.
But compared to that the hassle with explicit disable the warning is annoying.
So it schould be ok to disable the warning per file or even entirely.

[Holzhaus]

Could we make a custom "declare flags" macro that disables the warning, calls the "Qt declare flags" macro, then reenalbes the warning? Not sure if it's possible to put pragma into a macro.

If that's not possible, we can merge.

[Holzhaus]

LGTM, thank you.