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cmd/compile: miscompilation of codependent global var assigments in go1.12 [1.12 backport] #30996

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gopherbot opened this issue Mar 22, 2019 · 9 comments
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cmd/compile: miscompilation of codependent global var assigments in go1.12 [1.12 backport] #30996

gopherbot opened this issue Mar 22, 2019 · 9 comments
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CherryPickApproved Used during the release process for point releases FrozenDueToAge
Milestone
Go1.12.2

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@gopherbot
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@cherrymui requested issue #30977 to be considered for backport to the next 1.12 minor release.

@gopherbot please backport this to Go 1.12.
@gopherbot gopherbot added the CherryPickCandidate Used during the release process for point releases label Mar 22, 2019
@gopherbot gopherbot mentioned this issue Mar 22, 2019
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@gopherbot gopherbot added this to the Go1.12.2 milestone Mar 22, 2019
@gopherbot
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Change https://golang.org/cl/168817 mentions this issue: [release-branch.go1.12] cmd/compile: copy volatile values before emitting write barrier call

@bcmills bcmills changed the title cmd/go: miscompilation of codependent global var assigments in go1.12 [1.12 backport] cmd/compile: miscompilation of codependent global var assigments in go1.12 [1.12 backport] Mar 28, 2019
@thaJeztah
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@randall77 I saw you reviewed https://golang.org/cl/168817 - does that mean this should be labeled CherryPickApproved ?

@randall77
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No, that's still a call for the release guys to make.

Feel free to add pro-backport arguments to this issue.
I think it should be backported - it's a nasty bug with no easy workaround, and it was triggered in the wild.

@thaJeztah
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thaJeztah commented Apr 2, 2019 •
edited

Thanks for explaining (and apologies for being a bit noisy 🤗)

For our next release, this one is definitely a show-stopper, as the result is unpredictable. Timing is a bit unfortunate as we'll have to decide to proceed with Go 1.12, or revert all repositories to Go 1.11.

@bradfitz (I saw you applied the labels on other issues; so hope you're the right person to ask); ptal

@thaJeztah
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For my information; Is there any documentation about the Go release procedure? (or a mailinglist / meeting people can attend to stay informed?)

@randall77
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https://github.com/golang/go/wiki/MinorReleases

@randall77
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Also https://github.com/golang/go/wiki/Go-Release-Cycle

@thaJeztah
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Awesome, thanks!

@bradfitz bradfitz added the CherryPickApproved Used during the release process for point releases label Apr 2, 2019
@gopherbot gopherbot removed the CherryPickCandidate Used during the release process for point releases label Apr 2, 2019
@gopherbot
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Closed by merging 8acc2ea to release-branch.go1.12.

gopherbot pushed a commit that referenced this issue Apr 2, 2019
@cherrymui @bradfitz
[release-branch.go1.12] cmd/compile: copy volatile values before emit…
8acc2ea 
…ting write barrier call

It is possible that a "volatile" value (one that can be clobbered
by preparing args of a call) to be used in multiple write barrier
calls. We used to copy the volatile value right before each call.
But this doesn't work if the value is used the second time, after
the first call where it is already clobbered. Copy it before
emitting any call.

Updates #30977.
Fixes #30996.

Change-Id: Iedcc91ad848d5ded547bf37a8359c125d32e994c
Reviewed-on: https://go-review.googlesource.com/c/go/+/168677
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
(cherry picked from commit f23c601)
Reviewed-on: https://go-review.googlesource.com/c/go/+/168817
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
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@bradfitz @thaJeztah @randall77 @gopherbot