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cmd/compile: switch statement on a custom int32 type with negative values behaves differently in two consecutive calls [1.11 backport] #32582

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gopherbot opened this issue Jun 12, 2019 · 3 comments
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cmd/compile: switch statement on a custom int32 type with negative values behaves differently in two consecutive calls [1.11 backport] #32582

gopherbot opened this issue Jun 12, 2019 · 3 comments
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CherryPickApproved Used during the release process for point releases FrozenDueToAge
Milestone
Go1.11.12

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@gopherbot
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@josharian requested issue #32560 to be considered for backport to the next 1.11 minor release.

@gopherbot please open backport issues. This is an important compiler correctness bug with a safe, localized, minimal fix.
@gopherbot gopherbot added the CherryPickCandidate Used during the release process for point releases label Jun 12, 2019
@gopherbot gopherbot mentioned this issue Jun 12, 2019
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@gopherbot gopherbot added this to the Go1.11.12 milestone Jun 12, 2019
@gopherbot
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Change https://golang.org/cl/181979 mentions this issue: [release-branch.go1.11] cmd/compile: fix range analysis of small signed integers

@katiehockman
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Approving this cherry-pick since it is a localized, small risk change with no workaround.

@katiehockman katiehockman added CherryPickApproved Used during the release process for point releases and removed CherryPickCandidate Used during the release process for point releases labels Jun 17, 2019
gopherbot pushed a commit that referenced this issue Jul 1, 2019
@mdempsky @rsc
[release-branch.go1.11] cmd/compile: fix range analysis of small sign…
f056928 
…ed integers

For int8, int16, and int32, comparing their unsigned value to MaxInt64
to determine non-negativity doesn't make sense, because they have
negative values whose unsigned representation is smaller than that.
Fix is simply to compare with the appropriate upper bound based on the
value type's size.

Fixes #32582.

Change-Id: Ie7afad7a56af92bd890ba5ff33c86d1df06cfd9a
Reviewed-on: https://go-review.googlesource.com/c/go/+/181797
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
(cherry picked from commit f44404e)
Reviewed-on: https://go-review.googlesource.com/c/go/+/181979
Reviewed-by: Russ Cox <rsc@golang.org>
@rsc
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rsc commented Jul 1, 2019

Fixed by CL 181979 / f056928.

@rsc rsc closed this as completed Jul 1, 2019
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Go1.11.12
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