[llvm-dev] Self-hosting bots noise

[James Y Knight via llvm-dev]

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.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20151109/d6897b8e/attachment.html>