[llvm-dev] Self-hosting bots noise

James Y Knight via llvm-dev
2015-11-09T16:53:31Z

On Nov 9, 2015, at 11:42 AM, David Blaikie via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
>
>
> On Mon, Nov 9, 2015 at 4:32 AM, Renato Golin <renato.golin at linaro.org
<mailto: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).


I think he meant that the /second-stage/ build should always be done as a clean
build -- to make sure that all of the source gets rebuilt with the
newly-compiled compiler, instead of only rebuilding the modified sources with
the newly-built compiler.

Build systems typically aren't expected to watch out for the compiler itself
changing out from under them.
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