[go] cmd/cgo: don't emit C local if it is not used
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Ian Lance Taylor (Gerrit)
Dec 16, 2025, 7:01:27 PM (7 hours ago) Dec 16
to David Chase, goph...@pubsubhelper.golang.org, Ian Lance Taylor, golang-co...@googlegroups.com
Attention needed from David Chase
Ian Lance Taylor has uploaded the change for review![]( "Open in Gerrit")
Ian Lance Taylor would like David Chase to review this change.
Commit message
cmd/cgo: don't emit C local if it is not used
Fixes #76861
Change-Id: Icc8452e48ed736e8240f8afea18637c33b8e3ef8
Change diff
diff --git a/src/cmd/cgo/internal/test/issue76861.go b/src/cmd/cgo/internal/test/issue76861.go
new file mode 100644
index 0000000..225e2ac
--- /dev/null
+++ b/src/cmd/cgo/internal/test/issue76861.go
@@ -0,0 +1,12 @@
+// Copyright 2025 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.
+
+//go:build cgo
+
+package cgotest
+
+// Issue 43639: No runtime test needed, make sure package
+// cmd/cgo/internal/test/issue76861 compiles without error.
+
+import _ "cmd/cgo/internal/test/issue76861"
diff --git a/src/cmd/cgo/internal/test/issue76861/a.go b/src/cmd/cgo/internal/test/issue76861/a.go
new file mode 100644
index 0000000..18a7bda
--- /dev/null
+++ b/src/cmd/cgo/internal/test/issue76861/a.go
@@ -0,0 +1,13 @@
+// Copyright 2025 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 issue76861
+
+// #cgo CFLAGS: -Wall -Werror
+// void issue76861(void) {}
+import "C"
+
+func Issue76861() {
+ C.issue76861()
+}
diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go
index dc1e5b2..ac2ce8f 100644
--- a/src/cmd/cgo/out.go
+++ b/src/cmd/cgo/out.go
@@ -783,13 +783,13 @@
// We're trying to write a gcc struct that matches gc's layout.
// Use packed attribute to force no padding in this struct in case
// gcc has different packing requirements.
- fmt.Fprintf(fgcc, "\t%s %v *_cgo_a = v;\n", ctype, p.packedAttribute())
- if n.FuncType.Result != nil {
+ tr := n.FuncType.Result
+ if (n.Kind != "macro" && len(n.FuncType.Params) > 0) || tr != nil {
+ fmt.Fprintf(fgcc, "\t%s %v *_cgo_a = v;\n", ctype, p.packedAttribute())
+ }
+ if tr != nil {
// Save the stack top for use below.
fmt.Fprintf(fgcc, "\tchar *_cgo_stktop = _cgo_topofstack();\n")
- }
- tr := n.FuncType.Result
- if tr != nil {
fmt.Fprintf(fgcc, "\t__typeof__(_cgo_a->r) _cgo_r;\n")
}
fmt.Fprintf(fgcc, "\t_cgo_tsan_acquire();\n")
@@ -819,7 +819,7 @@
fmt.Fprintf(fgcc, "\t_cgo_errno = errno;\n")
}
fmt.Fprintf(fgcc, "\t_cgo_tsan_release();\n")
- if n.FuncType.Result != nil {
+ if tr != nil {
// The cgo call may have caused a stack copy (via a callback).
// Adjust the return value pointer appropriately.
fmt.Fprintf(fgcc, "\t_cgo_a = (void*)((char*)_cgo_a + (_cgo_topofstack() - _cgo_stktop));\n")
Change information
Files:
- A src/cmd/cgo/internal/test/issue76861.go
- A src/cmd/cgo/internal/test/issue76861/a.go
- M src/cmd/cgo/out.go
Change size: S
Delta: 3 files changed, 31 insertions(+), 6 deletions(-)
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Joe Richey (Gerrit)
Dec 16, 2025, 7:17:22 PM (7 hours ago) Dec 16
to Ian Lance Taylor, goph...@pubsubhelper.golang.org, Go LUCI, David Chase, golang-co...@googlegroups.com
Attention needed from David Chase and Ian Lance Taylor
Joe Richey voted and added 1 comment![]( "Open in Gerrit")
Votes added by Joe Richey
| Code-Review | +1 |
1 comment
Patchset-level comments
File-level comment, Patchset 1 (Latest):
Joe Richey . resolved
LGTM. The change and tests look good.
Thanks Ian for the quick fix!
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David Chase (Gerrit)
Dec 16, 2025, 9:41:49 PM (5 hours ago) Dec 16
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David Chase voted Code-Review+2![]( "Open in Gerrit")
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Ian Lance Taylor (Gerrit)
12:26 AM (2 hours ago) 12:26 AM
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Gopher Robot (Gerrit)
12:28 AM (2 hours ago) 12:28 AM
to Ian Lance Taylor, goph...@pubsubhelper.golang.org, golang-...@googlegroups.com, David Chase, Go LUCI, Joe Richey, golang-co...@googlegroups.com
Gopher Robot submitted the change![]( "Open in Gerrit")
Change information
Commit message:
cmd/cgo: don't emit C local if it is not used
Fixes #76861
Change-Id: Icc8452e48ed736e8240f8afea18637c33b8e3ef8
Reviewed-on: https://go-review.googlesource.com/c/go/+/730600
LUCI-TryBot-Result: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drc...@google.com>
Reviewed-by: Joe Richey <joer...@google.com>
Auto-Submit: Ian Lance Taylor <ia...@golang.org>
Files:
- A src/cmd/cgo/internal/test/issue76861.go
- A src/cmd/cgo/internal/test/issue76861/a.go
- M src/cmd/cgo/out.go
Change size: S
Delta: 3 files changed, 31 insertions(+), 6 deletions(-)
Branch: refs/heads/master
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Code-Review: +2 by David Chase, +1 by Joe Richey
TryBots-Pass: LUCI-TryBot-Result+1 by Go LUCI
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