Help with git bisect

[Jamie Walch]

I'm trying to trackdown a regression between 66.0.3341.0 and 66.0.3343.0 using git bisect. I got the hashes using omahaproxy.appspot.com for the two versions and I ran:

$ git bisect start

$ git bisect bad <hash1>

$ git bisect good <hash2>

Bisecting: a merge base must be tested

gclient runhooks

However, when I try to build (or even just run gn args), I get an error:

Generating files...

ERROR at //skia/BUILD.gn:350:5: Item not found

    "//third_party/skia/src/utils/SkDumpCanvas.cpp",

    ^----------------------------------------------

You were trying to remove "//third_party/skia/src/utils/SkDumpCanvas.cpp"

from the list but it wasn't there.

See //BUILD.gn:68:5: which caused the file to be included.

    "//skia:skia_unittests",

    ^----------------------

Any idea what's wrong and how I can fix it?

[Robert Sesek]

You probably need to do a full `gclient sync` and not just a runhooks, since the DEPS file may have changed. That is likely why GN cannot find the file.

- Robert

rsesek / @chromium.org

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[Christian Biesinger]

Did you gclient sync after the revision was checked out?

Christian

--

[Jamie Walch]

Thanks! Unfortunately that gives me a different error:

...

Syncing projects:  45% (54/118) src/chrome/browser/resources/media_router/extens

Syncing projects:  46% (55/118) src/chrome/test/data/perf/canvas_bench          

Syncing projects:  93% (75/80) src/third_party/ffmpeg                       

src/buildtools (ERROR)

----------------------------------------

[0:00:06] Started.

----------------------------------------

Error: Command 'git checkout --quiet 2637e7e911524502ea862870f52c36ed2723a25f' returned non-zero exit status 128 in /Users/jamiewalch/chromium/src/buildtools

fatal: reference is not a tree: 2637e7e911524502ea862870f52c36ed2723a25f

[Christian Biesinger]

Oh sorry, it needs to be "gclient sync --with_branch_heads"

Christian

[Jamie Walch]

Same problem :(

In case it's relevant, this is a fresh Chromium checkout on a new machine. I was able to build trunk, however, so I think I have it set up correctly.

[Tommy Nyquist]

I guess it also depends on whether your checkout is managed or not, but often when I do a bisect for something in src/, I typically add:

$ gclient sync -r src@HEAD

to keep the git repo I'm bisecting stable, but update the repos from DEPS.

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[Jamie Walch]

I'm pretty sure it's unmanaged (that's the default, right?) That command failed with the same error, but I can do the bisect on my Linux machine without any problems, and a colleague was able to do it on Mac, so there's something broken with my checkout, I just don't know how to work out what I'm missing.

[Robert Sesek]

That commit does appear to exist in buildtools (https://chromium.googlesource.com/chromium/buildtools/+/2637e7e911524502ea862870f52c36ed2723a25f), so maybe try deleting that directory locally and re-sync-ing?

rsesek / @chromium.org

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[Michael Giuffrida]

+1. You should be able to `cd` into the directory and see what Git thinks is happening. Make sure `git remote get-url origin` returns the expected repo URL and if all else false, manually run `git fetch` from that directory and reset to the given hash.

Some more tips for building old revisions here.

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[Jamie Walch]

Deleting the directory (and many, many others) fixed the problem. Thanks!