71 lines
2.2 KiB
Diff
71 lines
2.2 KiB
Diff
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From df5d4d3daab7e022335c0f3304d7b750bdd731a0 Mon Sep 17 00:00:00 2001
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From: Russ Cox <rsc@golang.org>
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Date: Tue, 15 Nov 2022 09:54:39 -0500
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Subject: [PATCH] [release-branch.go1.19] sync/atomic: allow linked list of atomic pointers again
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For #56603, CL 448275 added a _ [0]T field to atomic.Pointer,
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so that different kinds of atomic.Pointer are not convertible.
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Unfortunately, that breaks code like:
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type List struct {
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Next atomic.Pointer[List]
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}
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which should be valid, just as using Next *List is valid.
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Instead, we get:
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./atomic_test.go:2533:6: invalid recursive type List
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./atomic_test.go:2533:6: List refers to
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./atomic_test.go:2534:13: "sync/atomic".Pointer refers to
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./atomic_test.go:2533:6: List
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Fix by using _[0]*T instead.
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For #56638.
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Fixes #57124.
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Change-Id: Icc4c83c691d35961d20cb14b824223d6c779ac5e
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Reviewed-on: https://go-review.googlesource.com/c/go/+/450655
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Run-TryBot: Russ Cox <rsc@golang.org>
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TryBot-Result: Gopher Robot <gobot@golang.org>
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Reviewed-by: Michael Knyszek <mknyszek@google.com>
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(cherry picked from commit b14cf3d93ae5c477dd35f13f6ba41044f01a7f7d)
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Reviewed-on: https://go-review.googlesource.com/c/go/+/452438
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Reviewed-by: Cherry Mui <cherryyz@google.com>
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Run-TryBot: Michael Pratt <mpratt@google.com>
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Reviewed-by: Michael Pratt <mpratt@google.com>
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---
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diff --git a/src/sync/atomic/atomic_test.go b/src/sync/atomic/atomic_test.go
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index 02d55fb..3ab5e83 100644
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--- a/src/sync/atomic/atomic_test.go
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+++ b/src/sync/atomic/atomic_test.go
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@@ -2605,3 +2605,9 @@
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}()
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}
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}
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+
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+// Test that this compiles.
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+// When atomic.Pointer used _ [0]T, it did not.
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+type List struct {
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+ Next Pointer[List]
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+}
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diff --git a/src/sync/atomic/type.go b/src/sync/atomic/type.go
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index 2d1e621..93058ca 100644
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--- a/src/sync/atomic/type.go
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+++ b/src/sync/atomic/type.go
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@@ -37,9 +37,10 @@
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// A Pointer is an atomic pointer of type *T. The zero value is a nil *T.
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type Pointer[T any] struct {
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- // Mention T in a field to disallow conversion between Pointer types.
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+ // Mention *T in a field to disallow conversion between Pointer types.
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// See go.dev/issue/56603 for more details.
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- _ [0]T
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+ // Use *T, not T, to avoid spurious recursive type definition errors.
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+ _ [0]*T
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_ noCopy
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v unsafe.Pointer
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