Re: [PATCH v3 2/3] scripts/qapi-gen.py: add --add-trace-events option

[Paolo Bonzini]

On 1/18/22 15:22, Markus Armbruster wrote:
> > So, supporting auto-generated trace points for qga qmp commands requires some 
> > deeper refactoring.
> Similar trouble with tests?
>
> The normal case seems to be "generate trace code", with an exception for
> cases where our build system defeats that.  Agree?

More specifically, it's the lack of "include" statements: the only kind 
of include statement allowed by Meson is "include('foo/meson.build')" 
which is actually spelled "subdir('foo')".

What this would require is akin to

        include('qga/meson.qapi.build')
        include('tests/qapi/meson.qapi.build')
        include('trace/meson.build')
        ...
        include('qga/meson.build')

There has been an issue open in Meson forever about this: 
https://github.com/mesonbuild/meson/issues/375.  Some discussion can be 
found in https://github.com/mesonbuild/meson/pull/5209.

A somewhat ugly workaround would be something like

        subdir('qga/qapi')
        subdir('qapi')
        subdir('trace')
        ...
        subdir('qga')

Or even, move the .json files for qemu-ga and tests to qapi/qga and 
qapi/tests respectively.

That said, given that there's no tracing support in either trace nor in 
qemu-ga, I agree with Vladimir's assessment that there is no reason to 
do it.

Paolo



> If yes, I'd prefer to default to "generate trace code", and have an
> option to suppress it, with suitable TODO comment(s) explaining why.