runtime: panic if cleanup function closes over cleanup pointer

This would catch problems like https://go.dev/cl/696295.

Benchmark effect with this CL plus CL 697535:

goos: linux
goarch: amd64
pkg: runtime
cpu: 12th Gen Intel(R) Core(TM) i7-1260P
                     │ /tmp/foo.1  │             /tmp/foo.2             │
                     │   sec/op    │   sec/op     vs base               │
AddCleanupAndStop-16   81.93n ± 1%   82.87n ± 1%  +1.14% (p=0.041 n=10)

For #75066

Change-Id: Ia41d0d6b88baebf6055cb7e5d42bc8210b31630f
Reviewed-on: https://go-review.googlesource.com/c/go/+/714000
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

1 files changed, 25 insertions, 2 deletions

diff --git a/src/runtime/testdata/testprog/checkfinalizers.go b/src/runtime/testdata/testprog/checkfinalizers.go
index ea352a4e3e..9f082a25ff 100644
--- a/src/runtime/testdata/testprog/checkfinalizers.go
+++ b/src/runtime/testdata/testprog/checkfinalizers.go
@@ -28,17 +28,40 @@ func DetectFinalizerAndCleanupLeaks() {
 
 	// Leak a cleanup.
 	cLeak := new(T)
+
+	// Use an extra closure to avoid the simple
+	// checking done by AddCleanup.
+	var closeOverCLeak func(int)
+	closeOverCLeak = func(x int) {
+		// Use recursion to avoid inlining.
+		if x <= 0 {
+			**cLeak = x
+		} else {
+			closeOverCLeak(x - 1)
+		}
+	}
+
 	runtime.AddCleanup(cLeak, func(x int) {
-		**cLeak = x
+		closeOverCLeak(x)
 	}, int(0))
 
 	// Have a regular cleanup to make sure it doesn't trip the detector.
 	cNoLeak := new(T)
 	runtime.AddCleanup(cNoLeak, func(_ int) {}, int(0))
 
+	// Like closeOverCLeak.
+	var closeOverCNoLeak func(int)
+	closeOverCNoLeak = func(x int) {
+		if x <= 0 {
+			**cNoLeak = x
+		} else {
+			closeOverCNoLeak(x - 1)
+		}
+	}
+
 	// Add a cleanup that only temporarily leaks cNoLeak.
 	runtime.AddCleanup(cNoLeak, func(x int) {
-		**cNoLeak = x
+		closeOverCNoLeak(x)
 	}, int(0)).Stop()
 
 	if !asan.Enabled && !race.Enabled {