cmd/dlv,service/dap: use randomized name as default output binary

Using a fixed path as the default output binary means that executing
Delve twice in the same directory will cause the second invocation to
overwrite the output binary of the first instance of Delve, making the
restart command not work correctly.

Fixes #3345

Documentation/usage/dlv_debug.md

@@ -20,7 +20,7 @@ dlv debug [package] [flags]
 ```
       --continue        Continue the debugged process on start.
   -h, --help            help for debug
-      --output string   Output path for the binary. (default "./__debug_bin")
+      --output string   Output path for the binary.
       --tty string      TTY to use for the target program
 ```
 

Documentation/usage/dlv_test.md

@@ -23,7 +23,7 @@ dlv test [package] [flags]
 
 ```
   -h, --help            help for test
-      --output string   Output path for the binary. (default "debug.test")
+      --output string   Output path for the binary.
 ```
 
 ### Options inherited from parent commands

Documentation/usage/dlv_trace.md

@@ -24,7 +24,7 @@ dlv trace [package] regexp [flags]
       --ebpf            Trace using eBPF (experimental).
   -e, --exec string     Binary file to exec and trace.
   -h, --help            help for trace
-      --output string   Output path for the binary. (default "debug")
+      --output string   Output path for the binary.
   -p, --pid int         Pid to attach to.
   -s, --stack int       Show stack trace with given depth. (Ignored with --ebpf)
   -t, --test            Trace a test binary.

cmd/dlv/cmds/commands.go

@@ -230,7 +230,7 @@ package name and Delve will compile that package instead, and begin a new debug
 session.`,
 		Run: debugCmd,
 	}
-	debugCommand.Flags().String("output", "./__debug_bin", "Output path for the binary.")
+	debugCommand.Flags().String("output", "", "Output path for the binary.")
 	debugCommand.Flags().BoolVar(&continueOnStart, "continue", false, "Continue the debugged process on start.")
 	debugCommand.Flags().StringVar(&tty, "tty", "", "TTY to use for the target program")
 	rootCommand.AddCommand(debugCommand)
@@ -287,7 +287,7 @@ dlv test [package] -- -test.run TestSomething -test.v -other-argument
 See also: 'go help testflag'.`,
 		Run: testCmd,
 	}
-	testCommand.Flags().String("output", "debug.test", "Output path for the binary.")
+	testCommand.Flags().String("output", "", "Output path for the binary.")
 	rootCommand.AddCommand(testCommand)
 
 	// 'trace' subcommand.
@@ -311,7 +311,7 @@ only see the output of the trace operations you can redirect stdout.`,
 	traceCommand.Flags().BoolVarP(&traceUseEBPF, "ebpf", "", false, "Trace using eBPF (experimental).")
 	traceCommand.Flags().BoolVarP(&traceShowTimestamp, "timestamp", "", false, "Show timestamp in the output")
 	traceCommand.Flags().IntVarP(&traceStackDepth, "stack", "s", 0, "Show stack trace with given depth. (Ignored with --ebpf)")
-	traceCommand.Flags().String("output", "debug", "Output path for the binary.")
+	traceCommand.Flags().String("output", "", "Output path for the binary.")
 	rootCommand.AddCommand(traceCommand)
 
 	coreCommand := &cobra.Command{
@@ -528,10 +528,21 @@ func dapCmd(cmd *cobra.Command, args []string) {
 }
 
 func buildBinary(cmd *cobra.Command, args []string, isTest bool) (string, bool) {
-	debugname, err := filepath.Abs(cmd.Flag("output").Value.String())
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "%v\n", err)
-		return "", false
+	outputFlag := cmd.Flag("output").Value.String()
+	var debugname string
+	var err error
+	if outputFlag == "" {
+		if isTest {
+			debugname = gobuild.DefaultDebugBinaryPath("debug.test")
+		} else {
+			debugname = gobuild.DefaultDebugBinaryPath("__debug_bin")
+		}
+	} else {
+		debugname, err = filepath.Abs(outputFlag)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "%v\n", err)
+			return "", false
+		}
 	}
 
 	if isTest {
@@ -540,6 +551,9 @@ func buildBinary(cmd *cobra.Command, args []string, isTest bool) (string, bool)
 		err = gobuild.GoBuild(debugname, args, buildFlags)
 	}
 	if err != nil {
+		if outputFlag == "" {
+			gobuild.Remove(debugname)
+		}
 		fmt.Fprintf(os.Stderr, "%v\n", err)
 		return "", false
 	}

cmd/dlv/dlv_test.go

@@ -239,7 +239,7 @@ func getDlvBinInternal(t *testing.T, goflags ...string) string {
 func TestOutput(t *testing.T) {
 	dlvbin := getDlvBin(t)
 
-	for _, output := range []string{"", "myownname", filepath.Join(t.TempDir(), "absolute.path")} {
+	for _, output := range []string{"__debug_bin", "myownname", filepath.Join(t.TempDir(), "absolute.path")} {
 		testOutput(t, dlvbin, output, []string{"exit"})
 
 		const hello = "hello world!"
@@ -1327,3 +1327,39 @@ func TestStaticcheck(t *testing.T) {
 	out, _ := cmd.CombinedOutput()
 	checkAutogenDoc(t, "_scripts/staticcheck-out.txt", fmt.Sprintf("staticcheck %s > _scripts/staticcheck-out.txt", strings.Join(args, " ")), out)
 }
+
+func TestDefaultBinary(t *testing.T) {
+	// Check that when delve is run twice in the same directory simultaneously
+	// it will pick different default output binary paths.
+	dlvbin := getDlvBin(t)
+	fixture := filepath.Join(protest.FindFixturesDir(), "testargs.go")
+
+	startOne := func() (io.WriteCloser, func() error, *bytes.Buffer) {
+		cmd := exec.Command(dlvbin, "debug", "--allow-non-terminal-interactive=true", fixture, "--", "test")
+		stdin, _ := cmd.StdinPipe()
+		stdoutBuf := new(bytes.Buffer)
+		cmd.Stdout = stdoutBuf
+
+		assertNoError(cmd.Start(), t, "dlv debug")
+		return stdin, cmd.Wait, stdoutBuf
+	}
+
+	stdin1, wait1, stdoutBuf1 := startOne()
+	defer stdin1.Close()
+
+	stdin2, wait2, stdoutBuf2 := startOne()
+	defer stdin2.Close()
+
+	fmt.Fprintf(stdin1, "continue\nquit\n")
+	fmt.Fprintf(stdin2, "continue\nquit\n")
+
+	wait1()
+	wait2()
+
+	out1, out2 := stdoutBuf1.String(), stdoutBuf2.String()
+	t.Logf("%q", out1)
+	t.Logf("%q", out2)
+	if out1 == out2 {
+		t.Errorf("outputs match")
+	}
+}

pkg/gobuild/defaultexe.go

@@ -0,0 +1,28 @@
+package gobuild
+
+import (
+	"io/ioutil"
+	"runtime"
+
+	"github.com/go-delve/delve/pkg/logflags"
+)
+
+// DefaultDebugBinaryPath returns an unused file path in the current
+// directory named 'name' followed by a random string
+func DefaultDebugBinaryPath(name string) string {
+	pattern := name
+	if runtime.GOOS == "windows" {
+		pattern += "*.exe"
+	}
+	f, err := ioutil.TempFile(".", pattern)
+	if err != nil {
+		logflags.DebuggerLogger().Errorf("could not create temporary file for build output: %v", err)
+		if runtime.GOOS == "windows" {
+			return name + ".exe"
+		}
+		return name
+	}
+	r := f.Name()
+	f.Close()
+	return r
+}

service/dap/server.go

@@ -859,10 +859,6 @@ func (s *Session) setClientCapabilities(args dap.InitializeRequestArguments) {
 	s.clientCapabilities.supportsVariableType = args.SupportsVariableType
 }
 
-// Default output file pathname for the compiled binary in debug or test modes.
-// This is relative to the current working directory of the server.
-const defaultDebugBinary string = "./__debug_bin"
-
 func cleanExeName(name string) string {
 	if runtime.GOOS == "windows" && filepath.Ext(name) != ".exe" {
 		return name + ".exe"
@@ -957,8 +953,10 @@ func (s *Session) onLaunchRequest(request *dap.LaunchRequest) {
 	// Prepare the debug executable filename, building it if necessary
 	debugbinary := args.Program
 	if args.Mode == "debug" || args.Mode == "test" {
+		deleteOnError := false
 		if args.Output == "" {
-			args.Output = cleanExeName(defaultDebugBinary)
+			deleteOnError = true
+			args.Output = gobuild.DefaultDebugBinaryPath("__debug_bin")
 		} else {
 			args.Output = cleanExeName(args.Output)
 		}
@@ -981,6 +979,9 @@ func (s *Session) onLaunchRequest(request *dap.LaunchRequest) {
 		args.DlvCwd, _ = filepath.Abs(args.DlvCwd)
 		s.config.log.Debugf("building from %q: [%s]", args.DlvCwd, cmd)
 		if err != nil {
+			if deleteOnError {
+				gobuild.Remove(args.Output)
+			}
 			s.send(&dap.OutputEvent{
 				Event: *newEvent("output"),
 				Body: dap.OutputEventBody{
@@ -1049,6 +1050,9 @@ func (s *Session) onLaunchRequest(request *dap.LaunchRequest) {
 		s.debugger, err = debugger.New(&s.config.Debugger, s.config.ProcessArgs)
 	}()
 	if err != nil {
+		if s.binaryToRemove != "" {
+			gobuild.Remove(s.binaryToRemove)
+		}
 		s.sendShowUserErrorResponse(request.Request, FailedToLaunch, "Failed to launch", err.Error())
 		return
 	}