Revert "cmd/go, misc: switch from breakpoint to SIGUSR2"

This reverts commit 333f764d.

Replaced by a improved strategy later in the CL relation chain.

Change-Id: I70a1d2f0aa5aa0d3d0ec85b5a956c6fb60d88908
Reviewed-on: https://go-review.googlesource.com/36069
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

misc/ios/go_darwin_arm_exec.go

@@ -107,7 +107,7 @@ func main() {
 	// Approximately 1 in a 100 binaries fail to start. If it happens,
 	// try again. These failures happen for several reasons beyond
 	// our control, but all of them are safe to retry as they happen
-	// before lldb encounters the initial SIGUSR2 stop. As we
+	// before lldb encounters the initial getwd breakpoint. As we
 	// know the tests haven't started, we are not hiding flaky tests
 	// with this retry.
 	for i := 0; i < 5; i++ {
@@ -232,7 +232,6 @@ func run(bin string, args []string) (err error) {
 	s.do(`process handle SIGHUP  --stop false --pass true --notify false`)
 	s.do(`process handle SIGPIPE --stop false --pass true --notify false`)
 	s.do(`process handle SIGUSR1 --stop false --pass true --notify false`)
-	s.do(`process handle SIGUSR2 --stop true --pass false --notify true`) // sent by test harness
 	s.do(`process handle SIGCONT --stop false --pass true --notify false`)
 	s.do(`process handle SIGSEGV --stop false --pass true --notify false`) // does not work
 	s.do(`process handle SIGBUS  --stop false --pass true --notify false`) // does not work
@@ -245,9 +244,11 @@ func run(bin string, args []string) (err error) {
 		return nil
 	}
 
+	s.do(`breakpoint set -n getwd`) // in runtime/cgo/gcc_darwin_arm.go
+
 	started = true
 
-	s.doCmd("run", "stop reason = signal SIGUSR2", 20*time.Second)
+	s.doCmd("run", "stop reason = breakpoint", 20*time.Second)
 
 	// Move the current working directory into the faux gopath.
 	if pkgpath != "src" {

src/cmd/go/internal/test/test.go

@@ -907,13 +907,9 @@ func builderTest(b *work.Builder, p *load.Package) (buildAction, runAction, prin
 
 	if cfg.BuildContext.GOOS == "darwin" {
 		if cfg.BuildContext.GOARCH == "arm" || cfg.BuildContext.GOARCH == "arm64" {
-			t.IsIOS = true
-			t.NeedOS = true
+			t.NeedCgo = true
 		}
 	}
-	if t.TestMain == nil {
-		t.NeedOS = true
-	}
 
 	for _, cp := range pmain.Internal.Imports {
 		if len(cp.Internal.CoverVars) > 0 {
@@ -1360,8 +1356,7 @@ type testFuncs struct {
 	NeedTest    bool
 	ImportXtest bool
 	NeedXtest   bool
-	NeedOS      bool
-	IsIOS       bool
+	NeedCgo     bool
 	Cover       []coverInfo
 }
 
@@ -1475,7 +1470,7 @@ var testmainTmpl = template.Must(template.New("main").Parse(`
 package main
 
 import (
-{{if .NeedOS}}
+{{if not .TestMain}}
 	"os"
 {{end}}
 	"testing"
@@ -1491,10 +1486,8 @@ import (
 	_cover{{$i}} {{$p.Package.ImportPath | printf "%q"}}
 {{end}}
 
-{{if .IsIOS}}
-	"os/signal"
+{{if .NeedCgo}}
 	_ "runtime/cgo"
-	"syscall"
 {{end}}
 )
 
@@ -1560,12 +1553,6 @@ func coverRegisterFile(fileName string, counter []uint32, pos []uint32, numStmts
 {{end}}
 
 func main() {
-{{if .IsIOS}}
-	signal.Notify(make(chan os.Signal), syscall.SIGUSR2)
-	syscall.Kill(0, syscall.SIGUSR2)
-	signal.Reset(syscall.SIGUSR2)
-{{end}}
-
 {{if .CoverEnabled}}
 	testing.RegisterCover(testing.Cover{
 		Mode: {{printf "%q" .CoverMode}},