runtime: fix callee tracking in traceback printing

In CL 466099, we accidentally stopped tracking callees while unwinding
inlined frames during traceback printing. The effect is that if you
have a call stack like:

  f -> wrapper -> inlined into wrapper -> panic

when considering whether to print the frame for "wrapper", we'll think
that wrapper called panic, rather than the inlined function.

Fix this in the traceback code and add a test.

Change-Id: I30ec836cc316846ce93de94e28a650e23dca184e
Reviewed-on: https://go-review.googlesource.com/c/go/+/476579
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/src/runtime/stack_test.go b/src/runtime/stack_test.go
index 24f8290f67..9a096f5538 100644
--- a/src/runtime/stack_test.go
+++ b/src/runtime/stack_test.go
@@ -6,6 +6,7 @@ package runtime_test
 
 import (
 	"fmt"
+	"internal/testenv"
 	"reflect"
 	"regexp"
 	. "runtime"
@@ -652,6 +653,8 @@ func (s structWithMethod) stack() string {
 
 func (s structWithMethod) nop() {}
 
+func (s structWithMethod) inlinablePanic() { panic("panic") }
+
 func TestStackWrapperCaller(t *testing.T) {
 	var d structWithMethod
 	// Force the compiler to construct a wrapper method.
@@ -689,6 +692,33 @@ func TestStackWrapperStack(t *testing.T) {
 	}
 }
 
+func TestStackWrapperStackInlinePanic(t *testing.T) {
+	// Test that inline unwinding correctly tracks the callee by creating a
+	// stack of the form wrapper -> inlined function -> panic. If we mess up
+	// callee tracking, it will look like the wrapper called panic and we'll see
+	// the wrapper in the stack trace.
+	var d structWithMethod
+	wrapper := (*structWithMethod).inlinablePanic
+	defer func() {
+		err := recover()
+		if err == nil {
+			t.Fatalf("expected panic")
+		}
+		buf := make([]byte, 4<<10)
+		stk := string(buf[:Stack(buf, false)])
+		if strings.Contains(stk, "<autogenerated>") {
+			t.Fatalf("<autogenerated> appears in stack trace:\n%s", stk)
+		}
+		// Self-check: make sure inlinablePanic got inlined.
+		if !testenv.OptimizationOff() {
+			if !strings.Contains(stk, "inlinablePanic(...)") {
+				t.Fatalf("inlinablePanic not inlined")
+			}
+		}
+	}()
+	wrapper(&d)
+}
+
 type I interface {
 	M()
 }