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Issue metadata

Status: WontFix
Owner: ----
Closed: Jun 2017
Cc:
Components:
EstimatedDays: ----
NextAction: ----
OS: Linux
Pri: 3
Type: Bug



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v8 related code sometimes non-deterministic on debug build.

Project Member Reported by yyanagisawa@chromium.org, Oct 18 2016

Issue description

Build determinism will save on infrastructure utilization.  Most of the build on Linux are deterministic but I sometimes see binaries made from v8-related code are not.

https://uberchromegw.corp.google.com/i/chromium.fyi/builders/Linux%20deterministic%20%28dbg%29/builds/254/steps/compare_build_artifacts/logs/stdio
(snip)
Equals:           755
Expected diffs:   0
Unexpected diffs: 4
Unexpected files with diffs:

  cctest
  inspector-test
  libv8.so
  mksnapshot


I often see above four are different.
I doubt this is caused by difference between an object file compiled by goma and that compiled locally.  However, as far as I checked, the issue occurs for the case both files are built by goma, and I believe goma does not cause of the issue.
 

Comment 1 by mar...@chromium.org, Oct 18 2016

Components: Infra>Client>V8 Infra>Platform>Swarming
Do you want to assign the bug to the v8 team or do you want to try to handle it yourself?
Since this seems to only occur to V8 sources, I guess V8 team might know the reason.  I expect V8 team to fix this.
Cc: mstarzinger@chromium.org danno@chromium.org yangguo@chromium.org
This does not really ring a bell. These are executable binaries. Do you have more detailed information on which object files differ between builds?
Since it does not warn difference of object files, I guess link sometimes do something bad.  The strange thing is that they are not usually different but sometimes different.

https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Fchromium.fyi%2FLinux_deterministic%2F5096%2F%2B%2Frecipes%2Fsteps%2Fcompare_build_artifacts%2F0%2Fstdout
ppapi_nacl_tests_pnacl_newlib_x32_nonsfi.nexe        : DIFFERENT (unexpected): different size: 1843300 != 2309272
ppapi_nacl_tests_pnacl_newlib_x64.nexe               : DIFFERENT (unexpected): different size: 2541536 != 3007472
(snip)
Checking ppapi_nacl_tests_pnacl_newlib_x32_nonsfi.nexe difference: (181 deps)
Checking ppapi_nacl_tests_pnacl_newlib_x64.nexe difference: (181 deps)

This script is used for comparing difference of object files:
https://chromium.googlesource.com/chromium/src.git/+/master/tools/determinism/compare_build_artifacts.py
Components: -Infra>Platform>Swarming Infra>Goma
Status: WontFix (was: Untriaged)
We actually do not see this issue for long time?
https://uberchromegw.corp.google.com/i/chromium.fyi/builders/Linux%20deterministic%20%28dbg%29

the issue does not occur recently.

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