runtime: scan defer closure in stack scan

With stack objects, when we scan the stack, it scans defers with
tracebackdefers, but it seems to me that tracebackdefers doesn't
include the func value itself, which could be a stack allocated
closure. Scan it explicitly.

Alternatively, we can change tracebackdefers to include the func
value, which in turn needs to change the type of stkframe.

Fixes #30453.

Change-Id: I55a6e43264d6952ab2fa5c638bebb89fdc410e2b
Reviewed-on: https://go-review.googlesource.com/c/164118
Reviewed-by: Keith Randall <khr@golang.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/runtime/stack_test.go b/src/runtime/stack_test.go
index f52381710d..7bc63967bb 100644
--- a/src/runtime/stack_test.go
+++ b/src/runtime/stack_test.go
@@ -787,3 +787,11 @@ func TestTracebackAncestors(t *testing.T) {
 		}
 	}
 }
+
+// Test that defer closure is correctly scanned when the stack is scanned.
+func TestDeferLiveness(t *testing.T) {
+	output := runTestProg(t, "testprog", "DeferLiveness", "GODEBUG=clobberfree=1")
+	if output != "" {
+		t.Errorf("output:\n%s\n\nwant no output", output)
+	}
+}