[llvm-dev] Self-hosting bots noise

[David Blaikie via llvm-dev]

On Mon, Nov 9, 2015 at 4:32 AM, Renato Golin <renato.golin at linaro.org>
wrote:

> Hi David/Galina,
>
> FYI, I found one big reason why self-hosting bots fail long after the
> offending commit is tested: dirty builds.
>
> In a dirty build (no make clean), when a file X is changed that breaks
> file Y, the bot will only accuse the failure when file Y is changed,
> too, so that stage1 with modified X will compile file Y, and break.
>

That sounds like a bug in the build system - do you have any examples of
this? We should fix them.

The build should be reliable - any case where a clean build produces a
different result from a dirty build reduces/removes confidence in
incremental builds & hurts developer productivity (just like flakey tests,
etc).

- David


>
> At hindsight, it's obvious. But I hadn't connected the dots before... :/
>
> I'm moving all my self-hosting bots to clean builds and will be
> relying solely on ccache to make stage1 fast. This shall help with
> "breakages not on the blame list" problems.
>
> cheers,
> --renato
>
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