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sync/atomic: allow linked lists of atomic.Pointer [1.19 backport] #57124

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prattmic opened this issue Dec 6, 2022 · 2 comments
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sync/atomic: allow linked lists of atomic.Pointer [1.19 backport] #57124

prattmic opened this issue Dec 6, 2022 · 2 comments
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@mknyszek
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CherryPickApproved Used during the release process for point releases compiler/runtime Issues related to the Go compiler and/or runtime. FrozenDueToAge release-blocker
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Go1.19.5

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prattmic commented Dec 6, 2022

#56638 backported https://go.dev/cl/448275 as https://go.dev/cl/448518, which was released in Go 1.19.4.

This CL introduced a regression breaking compilation of atomic.Pointer[T] fields in T (such as linked list next pointers).

This regression is fixed in https://go.dev/cl/450655, sent as a backport in https://go.dev/cl/452438.

This backport did not make it into 1.19.4, so it should go into 1.19.5.
@prattmic prattmic added the CherryPickCandidate Used during the release process for point releases label Dec 6, 2022
@prattmic prattmic added this to the Go1.19.5 milestone Dec 6, 2022
@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Dec 6, 2022
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Change https://go.dev/cl/452438 mentions this issue: [release-branch.go1.19] sync/atomic: allow linked list of atomic pointers again

@cornelk cornelk mentioned this issue Dec 7, 2022
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@prattmic prattmic added the CherryPickApproved Used during the release process for point releases label Dec 7, 2022
@gopherbot gopherbot removed the CherryPickCandidate Used during the release process for point releases label Dec 7, 2022
@philhofer philhofer mentioned this issue Dec 8, 2022
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Closed by merging df5d4d3 to release-branch.go1.19.

gopherbot pushed a commit that referenced this issue Dec 9, 2022
@rsc @prattmic
[release-branch.go1.19] sync/atomic: allow linked list of atomic poin…
df5d4d3 
…ters again

For #56603, CL 448275 added a _ [0]T field to atomic.Pointer,
so that different kinds of atomic.Pointer are not convertible.

Unfortunately, that breaks code like:

	type List struct {
		Next atomic.Pointer[List]
	}

which should be valid, just as using Next *List is valid.
Instead, we get:

	./atomic_test.go:2533:6: invalid recursive type List
		./atomic_test.go:2533:6: List refers to
		./atomic_test.go:2534:13: "sync/atomic".Pointer refers to
		./atomic_test.go:2533:6: List

Fix by using _[0]*T instead.

For #56638.
Fixes #57124.

Change-Id: Icc4c83c691d35961d20cb14b824223d6c779ac5e
Reviewed-on: https://go-review.googlesource.com/c/go/+/450655
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
(cherry picked from commit b14cf3d)
Reviewed-on: https://go-review.googlesource.com/c/go/+/452438
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
@seankhliao seankhliao mentioned this issue Dec 20, 2022
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@HusseinElguindi HusseinElguindi mentioned this issue Dec 29, 2022
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@golang golang locked and limited conversation to collaborators Dec 9, 2023
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