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sync/atomic: atomic.Pointer[T] can be misused with type conversions. [1.19 backport] #56638

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gopherbot opened this issue Nov 8, 2022 · 4 comments
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sync/atomic: atomic.Pointer[T] can be misused with type conversions. [1.19 backport] #56638

gopherbot opened this issue Nov 8, 2022 · 4 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
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Go1.19.4

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@ianlancetaylor requested issue #56603 to be considered for backport to the next 1.19 minor release.

@gopherbot Please backport to 1.19.

This will make it less likely for people to write invalid type conversions with generic atomic types.
@gopherbot gopherbot added the CherryPickCandidate Used during the release process for point releases label Nov 8, 2022
@gopherbot gopherbot mentioned this issue Nov 8, 2022
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@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Nov 8, 2022
@gopherbot gopherbot added this to the Go1.19.4 milestone Nov 8, 2022
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Change https://go.dev/cl/448518 mentions this issue: [release-branch.go1.19] sync/atomic: disallow type conversions of atomic.Pointer[T]

@mknyszek mknyszek self-assigned this Nov 8, 2022
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mknyszek commented Nov 9, 2022

Consensus is that this is unlikely to break users but if it does, it's better to break them sooner rather than later to avoid these type conversions from propagating. Approving.

@mknyszek mknyszek added the CherryPickApproved Used during the release process for point releases label Nov 9, 2022
@gopherbot gopherbot removed the CherryPickCandidate Used during the release process for point releases label Nov 9, 2022
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Closed by merging 0dfdf32 to release-branch.go1.19.

gopherbot pushed a commit that referenced this issue Nov 11, 2022
@mateusz834 @mknyszek
[release-branch.go1.19] sync/atomic: disallow type conversions of ato…
0dfdf32 
…mic.Pointer[T]

For #56603.
Fixes #56638.

Change-Id: I6af9d80201025ae4028bfaa4a62e5de9ac0c501d
GitHub-Last-Rev: e6ed5e1
GitHub-Pull-Request: #56604
Reviewed-on: https://go-review.googlesource.com/c/go/+/448275
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
(cherry picked from commit 6bead8f)
Reviewed-on: https://go-review.googlesource.com/c/go/+/448518
Run-TryBot: Michael Knyszek <mknyszek@google.com>
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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

@prattmic prattmic mentioned this issue Dec 6, 2022
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andrew-d pushed a commit to tailscale/go that referenced this issue Dec 7, 2022
@mateusz834 @andrew-d
[release-branch.go1.19] sync/atomic: disallow type conversions of ato…
2c1ad7d 
…mic.Pointer[T]

For golang#56603.
Fixes golang#56638.

Change-Id: I6af9d80201025ae4028bfaa4a62e5de9ac0c501d
GitHub-Last-Rev: e6ed5e1
GitHub-Pull-Request: golang#56604
Reviewed-on: https://go-review.googlesource.com/c/go/+/448275
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
(cherry picked from commit 6bead8f)
Reviewed-on: https://go-review.googlesource.com/c/go/+/448518
Run-TryBot: Michael Knyszek <mknyszek@google.com>
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>
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