1385744 - build-clang.py doesn't handle the llvm source cache properly

Status: RESOLVED FIXED

(Firefox Build System :: General, enhancement)

Description

[Mike Hommey [:glandium]]

Windows clang-cl builds are using a llvm source cache, presumably to make the build faster, but it fails to use it properly, leading to surprising results. Most notably, if one tries to push a different branch than trunk and hit the cache, the result will still be from the trunk branch, because the svn update calls just update to the revision without doing anything about the repo url.

Comment 1

[Mike Hommey [:glandium]]

Attachment: Bug 1385744 - Stop using a cache for the llvm source.

The build-clang script doesn't handle properly updating the svn tree
when it already exists and the svn url changed (which happens when using
different branches), so if a clang job somehow gets a host that happen
to have run another clang job before, it may not actually build what
was intended to be built.

That event, however, is rather rare, because clang jobs don't happen
regularly enough. Fast iterations on try can cause the problem to
appear, though.

The former makes the use of a cache kind of useless, and the latter
barely benefits from the cache anyways. So let's just solve this the
easy way and remove the use of the cache. The alternative would be to
fiddle with svn switch, and I don't really feel like it.

Eventually, those jobs should use some other source than svn anyways,
one that is more verifiable (tarballs for releases, and the git mirrors
for trunk).

Review commit: https://reviewboard.mozilla.org/r/163876/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/163876/

Comment 2

[Gregory Szorc [:gps]]

Comment on attachment 8892862 [details]
Bug 1385744 - Stop using a cache for the llvm source.

https://reviewboard.mozilla.org/r/163876/#review169376

Caches are one of the hardest problems in computer science!

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/mozilla-central/rev/22ad2f44b6f8
Stop using a cache for the llvm source. r=gps