Fix for #614 and #683 (#687)

* service: Prevent panics from crashing delve and killing the target

Catch all unrecovered proc and debugger panics in the service layer and
report them as errors, allow users to cleanly detach from the target
and quit.

Fixes #614

* proc: Next/Step should not panic if line info can not be found.

Fixes #683

_fixtures/issue683.go

@@ -0,0 +1,7 @@
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("adssd") // put a breakpoint here
+}

dwarf/line/state_machine.go

@@ -3,6 +3,7 @@ package line
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 	"fmt"
 
 	"github.com/derekparker/delve/dwarf/util"
@@ -106,8 +107,13 @@ func (dbl *DebugLines) AllPCsForFileLine(f string, l int) (pcs []uint64) {
 	return
 }
 
-func (dbl *DebugLines) AllPCsBetween(begin, end uint64, filename string) []uint64 {
+var NoSourceError = errors.New("no source available")
+
+func (dbl *DebugLines) AllPCsBetween(begin, end uint64, filename string) ([]uint64, error) {
 	lineInfo := dbl.GetLineInfo(filename)
+	if lineInfo == nil {
+		return nil, NoSourceError
+	}
 	var (
 		pcs      []uint64
 		lastaddr uint64
@@ -125,7 +131,7 @@ func (dbl *DebugLines) AllPCsBetween(begin, end uint64, filename string) []uint6
 			pcs = append(pcs, sm.address)
 		}
 	}
-	return pcs
+	return pcs, nil
 }
 
 func findAndExecOpcode(sm *StateMachine, buf *bytes.Buffer, b byte) {

proc/proc_test.go

@@ -2357,3 +2357,25 @@ func TestNegativeIntEvaluation(t *testing.T) {
 		}
 	})
 }
+
+func TestIssue683(t *testing.T) {
+	// Step panics when source file can not be found
+	withTestProcess("issue683", t, func(p *Process, fixture protest.Fixture) {
+		_, err := setFunctionBreakpoint(p, "main.main")
+		assertNoError(err, t, "setFunctionBreakpoint()")
+		assertNoError(p.Continue(), t, "First Continue()")
+		goterror := false
+		for i := 0; i < 20; i++ {
+			// eventually an error about the source file not being found will be
+			// returned, the important thing is that we shouldn't panic
+			err := p.Step()
+			if err != nil {
+				goterror = true
+				break
+			}
+		}
+		if !goterror {
+			t.Fatal("expeceted an error we didn't get")
+		}
+	})
+}

proc/threads.go

@@ -159,6 +159,13 @@ func (dbp *Process) next(stepInto bool) error {
 		return err
 	}
 
+	success := false
+	defer func() {
+		if !success {
+			dbp.ClearInternalBreakpoints()
+		}
+	}()
+
 	csource := filepath.Ext(topframe.Current.File) != ".go"
 	thread := dbp.CurrentThread
 	currentGoroutine := false
@@ -182,14 +189,12 @@ func (dbp *Process) next(stepInto bool) error {
 
 			if instr.DestLoc != nil && instr.DestLoc.Fn != nil {
 				if err := dbp.setStepIntoBreakpoint([]AsmInstruction{instr}, cond); err != nil {
-					dbp.ClearInternalBreakpoints()
 					return err
 				}
 			} else {
 				// Non-absolute call instruction, set a StepBreakpoint here
 				if _, err := dbp.SetBreakpoint(instr.Loc.PC, StepBreakpoint, cond); err != nil {
 					if _, ok := err.(BreakpointExistsError); !ok {
-						dbp.ClearInternalBreakpoints()
 						return err
 					}
 				}
@@ -222,7 +227,6 @@ func (dbp *Process) next(stepInto bool) error {
 			bp, err := dbp.SetBreakpoint(deferpc, NextDeferBreakpoint, cond)
 			if err != nil {
 				if _, ok := err.(BreakpointExistsError); !ok {
-					dbp.ClearInternalBreakpoints()
 					return err
 				}
 			}
@@ -233,7 +237,10 @@ func (dbp *Process) next(stepInto bool) error {
 	}
 
 	// Add breakpoints on all the lines in the current function
-	pcs := dbp.lineInfo.AllPCsBetween(topframe.FDE.Begin(), topframe.FDE.End()-1, topframe.Current.File)
+	pcs, err := dbp.lineInfo.AllPCsBetween(topframe.FDE.Begin(), topframe.FDE.End()-1, topframe.Current.File)
+	if err != nil {
+		return err
+	}
 
 	if !csource {
 		var covered bool
@@ -254,6 +261,7 @@ func (dbp *Process) next(stepInto bool) error {
 
 	// Add a breakpoint on the return address for the current frame
 	pcs = append(pcs, topframe.Ret)
+	success = true
 	return dbp.setInternalBreakpoints(topframe.Current.PC, pcs, NextBreakpoint, cond)
 }
 

service/rpccommon/server.go

@@ -1,6 +1,7 @@
 package rpccommon
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"io"
@@ -10,6 +11,7 @@ import (
 	"net/rpc"
 	"net/rpc/jsonrpc"
 	"reflect"
+	"runtime"
 	"sync"
 	"unicode"
 	"unicode/utf8"
@@ -285,8 +287,18 @@ func (s *ServerImpl) serveJSONCodec(conn io.ReadWriteCloser) {
 		if mtype.Synchronous {
 			replyv = reflect.New(mtype.ReplyType.Elem())
 			function := mtype.method.Func
-			returnValues := function.Call([]reflect.Value{mtype.Rcvr, argv, replyv})
-			errInter := returnValues[0].Interface()
+			var returnValues []reflect.Value
+			var errInter interface{}
+			func() {
+				defer func() {
+					if ierr := recover(); ierr != nil {
+						errInter = newInternalError(ierr, 2)
+					}
+				}()
+				returnValues = function.Call([]reflect.Value{mtype.Rcvr, argv, replyv})
+				errInter = returnValues[0].Interface()
+			}()
+
 			errmsg := ""
 			if errInter != nil {
 				errmsg = errInter.(error).Error()
@@ -296,7 +308,14 @@ func (s *ServerImpl) serveJSONCodec(conn io.ReadWriteCloser) {
 		} else {
 			function := mtype.method.Func
 			ctl := &RPCCallback{s, sending, codec, req}
-			go function.Call([]reflect.Value{mtype.Rcvr, argv, reflect.ValueOf(ctl)})
+			go func() {
+				defer func() {
+					if ierr := recover(); ierr != nil {
+						ctl.Return(nil, newInternalError(ierr, 2))
+					}
+				}()
+				function.Call([]reflect.Value{mtype.Rcvr, argv, reflect.ValueOf(ctl)})
+			}()
 		}
 	}
 	codec.Close()
@@ -350,3 +369,41 @@ func (s *RPCServer) SetApiVersion(args api.SetAPIVersionIn, out *api.SetAPIVersi
 	s.s.config.APIVersion = args.APIVersion
 	return nil
 }
+
+type internalError struct {
+	Err   interface{}
+	Stack []internalErrorFrame
+}
+
+type internalErrorFrame struct {
+	Pc   uintptr
+	Func string
+	File string
+	Line int
+}
+
+func newInternalError(ierr interface{}, skip int) *internalError {
+	r := &internalError{ierr, nil}
+	for i := skip; ; i++ {
+		pc, file, line, ok := runtime.Caller(i)
+		if !ok {
+			break
+		}
+		fname := "<unknown>"
+		fn := runtime.FuncForPC(pc)
+		if fn != nil {
+			fname = fn.Name()
+		}
+		r.Stack = append(r.Stack, internalErrorFrame{pc, fname, file, line})
+	}
+	return r
+}
+
+func (err *internalError) Error() string {
+	var out bytes.Buffer
+	fmt.Fprintf(&out, "Internal debugger error: %v\n", err.Err)
+	for _, frame := range err.Stack {
+		fmt.Fprintf(&out, "%s (%#x)\n\t%s%d\n", frame.Func, frame.Pc, frame.File, frame.Line)
+	}
+	return out.String()
+}