proc: Do not panic when a command is executed on an exited process

Fixes #355

proc/proc.go

@@ -229,6 +229,9 @@ func (dbp *Process) CurrentLocation() (*Location, error) {
 // RequestManualStop sets the `halt` flag and
 // sends SIGSTOP to all threads.
 func (dbp *Process) RequestManualStop() error {
+	if dbp.exited {
+		return &ProcessExitedError{}
+	}
 	dbp.halt = true
 	return dbp.requestManualStop()
 }
@@ -237,6 +240,9 @@ func (dbp *Process) RequestManualStop() error {
 // break point table. Setting a break point must be thread specific due to
 // ptrace actions needing the thread to be in a signal-delivery-stop.
 func (dbp *Process) SetBreakpoint(addr uint64) (*Breakpoint, error) {
+	if dbp.exited {
+		return nil, &ProcessExitedError{}
+	}
 	return dbp.setBreakpoint(dbp.CurrentThread.ID, addr, false)
 }
 
@@ -247,6 +253,9 @@ func (dbp *Process) SetTempBreakpoint(addr uint64) (*Breakpoint, error) {
 
 // ClearBreakpoint clears the breakpoint at addr.
 func (dbp *Process) ClearBreakpoint(addr uint64) (*Breakpoint, error) {
+	if dbp.exited {
+		return nil, &ProcessExitedError{}
+	}
 	bp, ok := dbp.FindBreakpoint(addr)
 	if !ok {
 		return nil, NoBreakpointError{addr: addr}
@@ -268,6 +277,9 @@ func (dbp *Process) Status() *WaitStatus {
 
 // Next continues execution until the next source line.
 func (dbp *Process) Next() (err error) {
+	if dbp.exited {
+		return &ProcessExitedError{}
+	}
 	for i := range dbp.Breakpoints {
 		if dbp.Breakpoints[i].Temp {
 			return fmt.Errorf("next while nexting")
@@ -357,6 +369,9 @@ func (dbp *Process) setChanRecvBreakpoints() (int, error) {
 // process. It will continue until it hits a breakpoint
 // or is otherwise stopped.
 func (dbp *Process) Continue() error {
+	if dbp.exited {
+		return &ProcessExitedError{}
+	}
 	for {
 		if err := dbp.resume(); err != nil {
 			return err
@@ -498,6 +513,9 @@ func (dbp *Process) StepInstruction() (err error) {
 
 // SwitchThread changes from current thread to the thread specified by `tid`.
 func (dbp *Process) SwitchThread(tid int) error {
+	if dbp.exited {
+		return &ProcessExitedError{}
+	}
 	if th, ok := dbp.Threads[tid]; ok {
 		dbp.CurrentThread = th
 		dbp.SelectedGoroutine, _ = dbp.CurrentThread.GetG()
@@ -509,6 +527,9 @@ func (dbp *Process) SwitchThread(tid int) error {
 // SwitchGoroutine changes from current thread to the thread
 // running the specified goroutine.
 func (dbp *Process) SwitchGoroutine(gid int) error {
+	if dbp.exited {
+		return &ProcessExitedError{}
+	}
 	g, err := dbp.FindGoroutine(gid)
 	if err != nil {
 		return err
@@ -527,6 +548,9 @@ func (dbp *Process) SwitchGoroutine(gid int) error {
 // GoroutinesInfo returns an array of G structures representing the information
 // Delve cares about from the internal runtime G structure.
 func (dbp *Process) GoroutinesInfo() ([]*G, error) {
+	if dbp.exited {
+		return nil, &ProcessExitedError{}
+	}
 	if dbp.allGCache != nil {
 		return dbp.allGCache, nil
 	}
@@ -597,6 +621,9 @@ func (dbp *Process) GoroutinesInfo() ([]*G, error) {
 
 // Halt stops all threads.
 func (dbp *Process) Halt() (err error) {
+	if dbp.exited {
+		return &ProcessExitedError{}
+	}
 	for _, th := range dbp.Threads {
 		if err := th.Halt(); err != nil {
 			return err
@@ -817,6 +844,9 @@ func (dbp *Process) FindGoroutine(gid int) (*G, error) {
 // ConvertEvalScope returns a new EvalScope in the context of the
 // specified goroutine ID and stack frame.
 func (dbp *Process) ConvertEvalScope(gid, frame int) (*EvalScope, error) {
+	if dbp.exited {
+		return nil, &ProcessExitedError{}
+	}
 	g, err := dbp.FindGoroutine(gid)
 	if err != nil {
 		return nil, err

service/debugger/debugger.go

@@ -213,22 +213,29 @@ func (d *Debugger) FindBreakpoint(id int) *api.Breakpoint {
 }
 
 // Threads returns the threads of the target process.
-func (d *Debugger) Threads() []*api.Thread {
+func (d *Debugger) Threads() ([]*api.Thread, error) {
+	if d.process.Exited() {
+		return nil, &proc.ProcessExitedError{}
+	}
 	threads := []*api.Thread{}
 	for _, th := range d.process.Threads {
 		threads = append(threads, api.ConvertThread(th))
 	}
-	return threads
+	return threads, nil
 }
 
 // FindThread returns the thread for the given 'id'.
-func (d *Debugger) FindThread(id int) *api.Thread {
-	for _, thread := range d.Threads() {
+func (d *Debugger) FindThread(id int) (*api.Thread, error) {
+	threads, err := d.Threads()
+	if err != nil {
+		return nil, err
+	}
+	for _, thread := range threads {
 		if thread.ID == id {
-			return thread
+			return thread, nil
 		}
 	}
-	return nil
+	return nil, nil
 }
 
 // Command handles commands which control the debugger lifecycle

service/rpc/server.go

@@ -162,13 +162,16 @@ func (s *RPCServer) ClearBreakpoint(id int, breakpoint *api.Breakpoint) error {
 	return nil
 }
 
-func (s *RPCServer) ListThreads(arg interface{}, threads *[]*api.Thread) error {
-	*threads = s.debugger.Threads()
-	return nil
+func (s *RPCServer) ListThreads(arg interface{}, threads *[]*api.Thread) (err error) {
+	*threads, err = s.debugger.Threads()
+	return err
 }
 
 func (s *RPCServer) GetThread(id int, thread *api.Thread) error {
-	t := s.debugger.FindThread(id)
+	t, err := s.debugger.FindThread(id)
+	if err != nil {
+		return err
+	}
 	if t == nil {
 		return fmt.Errorf("no thread with id %d", id)
 	}
@@ -201,7 +204,11 @@ type ThreadListArgs struct {
 }
 
 func (s *RPCServer) ListThreadPackageVars(args *ThreadListArgs, variables *[]api.Variable) error {
-	if thread := s.debugger.FindThread(args.Id); thread == nil {
+	thread, err := s.debugger.FindThread(args.Id)
+	if err != nil {
+		return err
+	}
+	if thread == nil {
 		return fmt.Errorf("no thread with id %d", args.Id)
 	}
 

service/test/integration_test.go

@@ -28,6 +28,14 @@ func assertNoError(err error, t *testing.T, s string) {
 	}
 }
 
+func assertError(err error, t *testing.T, s string) {
+	if err == nil {
+		_, file, line, _ := runtime.Caller(1)
+		fname := filepath.Base(file)
+		t.Fatalf("failed assertion at %s:%d: %s (no error)\n", fname, line, s)
+	}
+}
+
 func TestMain(m *testing.M) {
 	os.Exit(protest.RunTestsWithFixtures(m))
 }
@@ -734,3 +742,59 @@ func TestClientServer_FullStacktrace(t *testing.T) {
 		}
 	})
 }
+
+func TestIssue355(t *testing.T) {
+	// After the target process has terminated should return an error but not crash
+	withTestClient("continuetestprog", t, func(c service.Client) {
+		bp, err := c.CreateBreakpoint(&api.Breakpoint{FunctionName: "main.sayhi", Line: -1})
+		assertNoError(err, t, "CreateBreakpoint()")
+		ch := c.Continue()
+		state := <-ch
+		tid := state.CurrentThread.ID
+		gid := state.SelectedGoroutine.ID
+		assertNoError(state.Err, t, "First Continue()")
+		ch = c.Continue()
+		state = <-ch
+		if !state.Exited {
+			t.Fatalf("Target did not terminate after second continue")
+		}
+
+		ch = c.Continue()
+		state = <-ch
+		assertError(state.Err, t, "Continue()")
+
+		_, err = c.Next()
+		assertError(err, t, "Next()")
+		_, err = c.Step()
+		assertError(err, t, "Step()")
+		_, err = c.StepInstruction()
+		assertError(err, t, "StepInstruction()")
+		_, err = c.SwitchThread(tid)
+		assertError(err, t, "SwitchThread()")
+		_, err = c.SwitchGoroutine(gid)
+		assertError(err, t, "SwitchGoroutine()")
+		_, err = c.Halt()
+		assertError(err, t, "Halt()")
+		_, err = c.CreateBreakpoint(&api.Breakpoint{FunctionName: "main.main", Line: -1})
+		assertError(err, t, "CreateBreakpoint()")
+		_, err = c.ClearBreakpoint(bp.ID)
+		assertError(err, t, "ClearBreakpoint()")
+		_, err = c.ListThreads()
+		assertError(err, t, "ListThreads()")
+		_, err = c.GetThread(tid)
+		assertError(err, t, "GetThread()")
+		assertError(c.SetVariable(api.EvalScope{gid, 0}, "a", "10"), t, "SetVariable()")
+		_, err = c.ListLocalVariables(api.EvalScope{gid, 0})
+		assertError(err, t, "ListLocalVariables()")
+		_, err = c.ListFunctionArgs(api.EvalScope{gid, 0})
+		assertError(err, t, "ListFunctionArgs()")
+		_, err = c.ListRegisters()
+		assertError(err, t, "ListRegisters()")
+		_, err = c.ListGoroutines()
+		assertError(err, t, "ListGoroutines()")
+		_, err = c.Stacktrace(gid, 10, false)
+		assertError(err, t, "Stacktrace()")
+		_, err = c.FindLocation(api.EvalScope{gid, 0}, "+1")
+		assertError(err, t, "FindLocation()")
+	})
+}