runtime: fix TestDeferWithRepeatedRepanics and TestIssue37688 to be less chatty

Converted some Println() statements (used to make sure that certain variables were
kept alive and not optimized out) to assignments into global variables, so the
tests don't produce extraneous output when there is a failure.

Fixes #38594

Change-Id: I7eb41bb02b2b1e78afd7849676b5c85bc11c759c
Reviewed-on: https://go-review.googlesource.com/c/go/+/229538
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/defer_test.go

@@ -6,7 +6,6 @@ package runtime_test
 
 import (
 	"fmt"
-	"os"
 	"reflect"
 	"runtime"
 	"testing"
@@ -325,11 +324,13 @@ func recurseFnPanicRec(level int, maxlevel int) {
 	recurseFn(level, maxlevel)
 }
 
+var saveInt uint32
+
 func recurseFn(level int, maxlevel int) {
 	a := [40]uint32{0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff}
 	if level+1 < maxlevel {
-		// Need this print statement to keep a around.  '_ = a[4]' doesn't do it.
-		fmt.Fprintln(os.Stderr, "recurseFn", level, a[4])
+		// Make sure a array is referenced, so it is not optimized away
+		saveInt = a[4]
 		recurseFn(level+1, maxlevel)
 	} else {
 		panic("recurseFn panic")
@@ -350,12 +351,12 @@ func TestIssue37688(t *testing.T) {
 type foo struct {
 }
 
+//go:noinline
 func (f *foo) method1() {
-	fmt.Fprintln(os.Stderr, "method1")
 }
 
+//go:noinline
 func (f *foo) method2() {
-	fmt.Fprintln(os.Stderr, "method2")
 }
 
 func g2() {
@@ -379,6 +380,10 @@ func g3() {
 	g2()
 }
 
+var globstruct struct {
+	a, b, c, d, e, f, g, h, i int
+}
+
 func ff1(ap *foo, a, b, c, d, e, f, g, h, i int) {
 	defer ap.method1()
 
@@ -387,9 +392,15 @@ func ff1(ap *foo, a, b, c, d, e, f, g, h, i int) {
 	// defer pool)
 	defer func(ap *foo, a, b, c, d, e, f, g, h, i int) {
 		if v := recover(); v != nil {
-			fmt.Fprintln(os.Stderr, "did recover")
 		}
-		fmt.Fprintln(os.Stderr, "debug", ap, a, b, c, d, e, f, g, h)
+		globstruct.a = a
+		globstruct.b = b
+		globstruct.c = c
+		globstruct.d = d
+		globstruct.e = e
+		globstruct.f = f
+		globstruct.g = g
+		globstruct.h = h
 	}(ap, a, b, c, d, e, f, g, h, i)
 	panic("ff1 panic")
 }
@@ -397,7 +408,5 @@ func ff1(ap *foo, a, b, c, d, e, f, g, h, i int) {
 func rec1(max int) {
 	if max > 0 {
 		rec1(max - 1)
-	} else {
-		fmt.Fprintln(os.Stderr, "finished recursion", max)
 	}
 }