cmd/go: fix "go run" cgo source when cgo is disabled

also move a cgo-depend test to appropriate source file in runtime.

R=golang-dev, dave, adg, rsc
CC=golang-dev
https://golang.org/cl/7393063

src/cmd/go/run.go

@@ -68,8 +68,16 @@ func runRun(cmd *Command, args []string) {
 	var src string
 	if len(p.GoFiles) > 0 {
 		src = p.GoFiles[0]
-	} else {
+	} else if len(p.CgoFiles) > 0 {
 		src = p.CgoFiles[0]
+	} else {
+		// this case could only happen if the provided source uses cgo
+		// while cgo is disabled.
+		hint := ""
+		if !buildContext.CgoEnabled {
+			hint = " (cgo is disabled)"
+		}
+		fatalf("go run: no suitable source files%s", hint)
 	}
 	p.exeName = src[:len(src)-len(".go")] // name temporary executable for first go file
 	a1 := b.action(modeBuild, modeBuild, p)

src/pkg/runtime/crash_cgo_test.go

@@ -13,3 +13,76 @@ import (
 func TestCgoCrashHandler(t *testing.T) {
 	testCrashHandler(t, true)
 }
+
+func TestCgoSignalDeadlock(t *testing.T) {
+	got := executeTest(t, cgoSignalDeadlockSource, nil)
+	want := "OK\n"
+	if got != want {
+		t.Fatalf("expected %q, but got %q", want, got)
+	}
+}
+
+const cgoSignalDeadlockSource = `
+package main
+
+import "C"
+
+import (
+	"fmt"
+	"runtime"
+	"time"
+)
+
+func main() {
+	runtime.GOMAXPROCS(100)
+	ping := make(chan bool)
+	go func() {
+		for i := 0; ; i++ {
+			runtime.Gosched()
+			select {
+			case done := <-ping:
+				if done {
+					ping <- true
+					return
+				}
+				ping <- true
+			default:
+			}
+			func() {
+				defer func() {
+					recover()
+				}()
+				var s *string
+				*s = ""
+			}()
+		}
+	}()
+	time.Sleep(time.Millisecond)
+	for i := 0; i < 64; i++ {
+		go func() {
+			runtime.LockOSThread()
+			select {}
+		}()
+		go func() {
+			runtime.LockOSThread()
+			select {}
+		}()
+		time.Sleep(time.Millisecond)
+		ping <- false
+		select {
+		case <-ping:
+		case <-time.After(time.Second):
+			fmt.Printf("HANG\n")
+			return
+		}
+	}
+	ping <- true
+	select {
+	case <-ping:
+	case <-time.After(time.Second):
+		fmt.Printf("HANG\n")
+		return
+	}
+	fmt.Printf("OK\n")
+}
+`

src/pkg/runtime/crash_test.go

@@ -99,14 +99,6 @@ func TestLockedDeadlock2(t *testing.T) {
 	testDeadlock(t, lockedDeadlockSource2)
 }
 
-func TestCgoSignalDeadlock(t *testing.T) {
-	got := executeTest(t, cgoSignalDeadlockSource, nil)
-	want := "OK\n"
-	if got != want {
-		t.Fatalf("expected %q, but got %q", want, got)
-	}
-}
-
 const crashSource = `
 package main
 
@@ -191,68 +183,3 @@ func main() {
 	select {}
 }
 `
-
-const cgoSignalDeadlockSource = `
-package main
-
-import "C"
-
-import (
-	"fmt"
-	"runtime"
-	"time"
-)
-
-func main() {
-	runtime.GOMAXPROCS(100)
-	ping := make(chan bool)
-	go func() {
-		for i := 0; ; i++ {
-			runtime.Gosched()
-			select {
-			case done := <-ping:
-				if done {
-					ping <- true
-					return
-				}
-				ping <- true
-			default:
-			}
-			func() {
-				defer func() {
-					recover()
-				}()
-				var s *string
-				*s = ""
-			}()
-		}
-	}()
-	time.Sleep(time.Millisecond)
-	for i := 0; i < 64; i++ {
-		go func() {
-			runtime.LockOSThread()
-			select {}
-		}()
-		go func() {
-			runtime.LockOSThread()
-			select {}
-		}()
-		time.Sleep(time.Millisecond)
-		ping <- false
-		select {
-		case <-ping:
-		case <-time.After(time.Second):
-			fmt.Printf("HANG\n")
-			return
-		}
-	}
-	ping <- true
-	select {
-	case <-ping:
-	case <-time.After(time.Second):
-		fmt.Printf("HANG\n")
-		return
-	}
-	fmt.Printf("OK\n")
-}
-`