On Wednesday, 15 June 2016 at 05:04:28 UTC, Jason White wrote:
If you want to depend on the compiler version, then you can add a dependency on the compiler executable. It might be a good idea to have Button do this automatically for every command. That is, finding the path to the command's executable and making it a dependency.

I think you are fine if adding a dependency works. If it's done automatically someone will ask for a way to disable this feature.

However, I can think of another scenario where it would just as well be incorrect behavior: Linking an executable and then running tests on it. The executable could then be seen by the build system as the "secondary" or "intermediate" output. If it gets deleted, I think we'd want it rebuilt.

I'm not sure how Make or Shake implement this without doing it incorrectly in certain scenarios. There would need to be a way to differentiate between necessary and unnecessary outputs. I'll have to think about this more.

Shake has 'order only' dependencies that cover the 'intermediate' case. GNU make supports special targets '.INTERMEDIATE' and '.SECONDARY' [1].

[1] http://www.gnu.org/software/make/manual/make.html#Chained-Rules

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