[CMake] How to deal with generated source files (w/ dependency tracking) for globs

[Eric Wing]

On 4/4/16, Nicholas Braden <nicholas11braden at gmail.com> wrote:
> I haven't tested this myself, but instead of using a glob, you could
> have a build step that generates a CMake script file with the list of
> generated files in it (e.g. via execute_process to run another CMake
> script whose only job is to generate the CMake script inception-style)
> and just include the generated file - CMake will see that the CMake
> file has been modified during every build but will still handle source
> file changes correctly. Worth a shot.
>

Thanks for the reply. So if I understand this correctly, this is what
the workflow is going to feel like.

- User adds their Nim file to the CMakeLists.txt
- CMake detects a change and a bootstrap generate/update takes place,
and my stuff re-runs the Nim compiler.
- Also during this phase, I need to generate another CMake script
which contains the list of files the Nim compiler output.
- Since this other script is also under CMake change tracking, this
will trigger another CMake change detection and
bootstrap/generate/update.
- Now the generated build system has the updated list of generated .c
files to compile and will finally compile it.

Does this sound right?

My major concern is that the two bootstrap phases kind of break the
flow. What I mean by that is that in Xcode for example, when a
bootstrap/generate/update happens, it actually causes your Build/Run
(run button) action to abort midway through. You sit there expecting
it to build, but CMake's regeneration was the only thing that
happened. You must hit the Run button again to actually build/run.
Kind of annoying and also really confusing for people who don't
understand this because it isn't obvious why this happened.

But in the above example, there are now two bootstrap phases. So
assuming this works, I think the user will have to hit the Run button
at least 3 times before something actually builds/runs. I think this
is going to feel real broken and feel like dumb luck something
actually built.

So I was hoping to find a one-step bootstrap solution instead of two-step.

Thanks,
Eric