[go] reflect: use &zeroVal[0] instead of nil for data field for zero-sized payloads
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Keith Randall (Gerrit)
Feb 24, 2026, 6:37:15 PM (10 hours ago) Feb 24
to Cuong Manh Le, goph...@pubsubhelper.golang.org, Keith Randall, golang-co...@googlegroups.com
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Commit message
reflect: use &zeroVal[0] instead of nil for data field for zero-sized payloads
Because our wrapper functions barf if the pointer is nil, even if
we don't actually dereference the pointer.
Fixes #77779
Change-Id: Ib1b93d9f0fdc771cd884137007508ba2b1da4b7a
Change diff
diff --git a/src/reflect/value.go b/src/reflect/value.go
index 6fba1e7..e4a686c 100644
--- a/src/reflect/value.go
+++ b/src/reflect/value.go
@@ -1288,9 +1288,10 @@
// bunch of zero-sized fields. We must return the zero-sized
// fields indirectly, as only ptr-shaped things can be direct.
// See issue 74935.
- // We use nil instead of v.ptr as it doesn't matter and
+ // We use &zeroVal[0] instead of v.ptr as it doesn't matter and
// we can avoid pinning a possibly now-unused object.
- return Value{typ, nil, fl | flagIndir}
+ // Don't use nil, see issue 77779.
+ return Value{typ, unsafe.Pointer(&zeroVal[0]), fl | flagIndir}
}
// Either flagIndir is set and v.ptr points at struct,
diff --git a/test/fixedbugs/issue77779.go b/test/fixedbugs/issue77779.go
new file mode 100644
index 0000000..1a61b2c
--- /dev/null
+++ b/test/fixedbugs/issue77779.go
@@ -0,0 +1,45 @@
+// run
+
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+ "reflect"
+)
+
+type Renderer interface {
+ Render() error
+}
+
+type ZeroSize struct{}
+
+func (ZeroSize) Render() error { return nil }
+
+type Data struct {
+ X, Y, Z int
+}
+
+// Container is pointer-sized (8 bytes): zero-size embed + one pointer field.
+// This triggers Go 1.26 interface inlining, which produces a nil data pointer
+// for the zero-size field when extracted via reflect.Value.Interface().
+type Container struct {
+ ZeroSize
+ Data *Data
+}
+
+func main() {
+ render(Container{})
+ render(&Container{})
+}
+
+func render(iface any) {
+ if reflect.ValueOf(iface).Kind() == reflect.Ptr {
+ _ = reflect.ValueOf(iface).Elem().Field(0).Interface().(Renderer).Render()
+ return
+ }
+
+ _ = reflect.ValueOf(iface).Field(0).Interface().(Renderer).Render()
+}
Change information
Files:
- M src/reflect/value.go
- A test/fixedbugs/issue77779.go
Change size: M
Delta: 2 files changed, 48 insertions(+), 2 deletions(-)
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Ian Lance Taylor (Gerrit)
Feb 24, 2026, 6:39:18 PM (10 hours ago) Feb 24
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Cuong Manh Le (Gerrit)
Feb 24, 2026, 7:09:23 PM (10 hours ago) Feb 24
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Cherry Mui (Gerrit)
Feb 24, 2026, 11:13:25 PM (6 hours ago) Feb 24
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Keith Randall (Gerrit)
Feb 24, 2026, 11:51:11 PM (5 hours ago) Feb 24
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Keith Randall (Gerrit)
Feb 24, 2026, 11:51:22 PM (5 hours ago) Feb 24
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Change information
Commit message:
reflect: use &zeroVal[0] instead of nil for data field for zero-sized payloads
Because our wrapper functions barf if the pointer is nil, even if
we don't actually dereference the pointer.
Fixes #77779
Change-Id: Ib1b93d9f0fdc771cd884137007508ba2b1da4b7a
Reviewed-on: https://go-review.googlesource.com/c/go/+/748660
Reviewed-by: Ian Lance Taylor <ia...@golang.org>
LUCI-TryBot-Result: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cuong Manh Le <cuong.m...@gmail.com>
Reviewed-by: Cherry Mui <cher...@google.com>
Reviewed-by: Keith Randall <k...@google.com>
Files:
- M src/reflect/value.go
- A test/fixedbugs/issue77779.go
Change size: M
Delta: 2 files changed, 48 insertions(+), 2 deletions(-)
Branch: refs/heads/master
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Keith Randall (Gerrit)
Feb 24, 2026, 11:52:30 PM (5 hours ago) Feb 24
to goph...@pubsubhelper.golang.org, Keith Randall, golang-co...@googlegroups.com
Keith Randall has uploaded the change for review![]( "Open in Gerrit")
Commit message
[release-branch.go1.26] reflect: use &zeroVal[0] instead of nil for data field for zero-sized payloads
Because our wrapper functions barf if the pointer is nil, even if
we don't actually dereference the pointer.
Fixes #77780
Change-Id: Ib1b93d9f0fdc771cd884137007508ba2b1da4b7a
Reviewed-on: https://go-review.googlesource.com/c/go/+/748660
Reviewed-by: Ian Lance Taylor <ia...@golang.org>
LUCI-TryBot-Result: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cuong Manh Le <cuong.m...@gmail.com>
Reviewed-by: Cherry Mui <cher...@google.com>
Reviewed-by: Keith Randall <k...@google.com>
(cherry picked from commit 60dc96479a85db0e245a5c14d964628169abedf4)
Change diff
diff --git a/src/reflect/value.go b/src/reflect/value.go
index 8c8acba..f192eb5 100644
Change information
Files:
- M src/reflect/value.go
- A test/fixedbugs/issue77779.go
Change size: M
Delta: 2 files changed, 48 insertions(+), 2 deletions(-)
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Keith Randall (Gerrit)
Feb 24, 2026, 11:53:03 PM (5 hours ago) Feb 24
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Keith Randall (Gerrit)
Feb 24, 2026, 11:53:30 PM (5 hours ago) Feb 24
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Cuong Manh Le (Gerrit)
12:20 AM (5 hours ago) 12:20 AM
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