terminal,service: add API and commands for watchpoints (#2488)

Adds API calls and terminal commands to set watchpoints.

Documentation/cli/README.md

@@ -34,6 +34,7 @@ Command | Description
 [on](#on) | Executes a command when a breakpoint is hit.
 [toggle](#toggle) | Toggles on or off a breakpoint.
 [trace](#trace) | Set tracepoint.
+[watch](#watch) | Set watchpoint.
 
 
 ## Viewing program variables and memory
@@ -581,6 +582,24 @@ Print package variables.
 If regex is specified only package variables with a name matching it will be returned. If -v is specified more information about each package variable will be shown.
 
 
+## watch
+Set watchpoint.
+	
+	watch [-r|-w|-rw] <expr>
+	
+	-r	stops when the memory location is read
+	-w	stops when the memory location is written
+	-rw	stops when the memory location is read or written
+
+The memory location is specified with the same expression language used by 'print', for example:
+
+	watch v
+
+will watch the address of variable 'v'.
+
+See also: "help print".
+
+
 ## whatis
 Prints type of an expression.
 

Documentation/cli/starlark.md

@@ -26,6 +26,7 @@ clear_breakpoint(Id, Name) | Equivalent to API call [ClearBreakpoint](https://go
 clear_checkpoint(ID) | Equivalent to API call [ClearCheckpoint](https://godoc.org/github.com/go-delve/delve/service/rpc2#RPCServer.ClearCheckpoint)
 raw_command(Name, ThreadID, GoroutineID, ReturnInfoLoadConfig, Expr, UnsafeCall) | Equivalent to API call [Command](https://godoc.org/github.com/go-delve/delve/service/rpc2#RPCServer.Command)
 create_breakpoint(Breakpoint) | Equivalent to API call [CreateBreakpoint](https://godoc.org/github.com/go-delve/delve/service/rpc2#RPCServer.CreateBreakpoint)
+create_watchpoint(Scope, Expr, Type) | Equivalent to API call [CreateWatchpoint](https://godoc.org/github.com/go-delve/delve/service/rpc2#RPCServer.CreateWatchpoint)
 detach(Kill) | Equivalent to API call [Detach](https://godoc.org/github.com/go-delve/delve/service/rpc2#RPCServer.Detach)
 disassemble(Scope, StartPC, EndPC, Flavour) | Equivalent to API call [Disassemble](https://godoc.org/github.com/go-delve/delve/service/rpc2#RPCServer.Disassemble)
 dump_cancel() | Equivalent to API call [DumpCancel](https://godoc.org/github.com/go-delve/delve/service/rpc2#RPCServer.DumpCancel)

pkg/proc/breakpoints.go

@@ -35,6 +35,7 @@ type Breakpoint struct {
 	Name         string // User defined name of the breakpoint
 	LogicalID    int    // ID of the logical breakpoint that owns this physical breakpoint
 
+	WatchExpr    string
 	WatchType    WatchType
 	HWBreakIndex uint8 // hardware breakpoint index
 
@@ -316,7 +317,11 @@ func (t *Target) SetWatchpoint(scope *EvalScope, expr string, wtype WatchType, c
 		return nil, errors.New("can not watch stack allocated variable")
 	}
 
-	return t.setBreakpointInternal(xv.Addr, UserBreakpoint, wtype.withSize(uint8(sz)), cond)
+	bp, err := t.setBreakpointInternal(xv.Addr, UserBreakpoint, wtype.withSize(uint8(sz)), cond)
+	if bp != nil {
+		bp.WatchExpr = expr
+	}
+	return bp, err
 }
 
 func (t *Target) setBreakpointInternal(addr uint64, kind BreakpointKind, wtype WatchType, cond ast.Expr) (*Breakpoint, error) {

pkg/terminal/command.go

@@ -130,6 +130,21 @@ See also: "help on", "help cond" and "help clear"`},
 A tracepoint is a breakpoint that does not stop the execution of the program, instead when the tracepoint is hit a notification is displayed. See $GOPATH/src/github.com/go-delve/delve/Documentation/cli/locspec.md for the syntax of linespec.
 
 See also: "help on", "help cond" and "help clear"`},
+		{aliases: []string{"watch"}, group: breakCmds, cmdFn: watchpoint, helpMsg: `Set watchpoint.
+	
+	watch [-r|-w|-rw] <expr>
+	
+	-r	stops when the memory location is read
+	-w	stops when the memory location is written
+	-rw	stops when the memory location is read or written
+
+The memory location is specified with the same expression language used by 'print', for example:
+
+	watch v
+
+will watch the address of variable 'v'.
+
+See also: "help print".`},
 		{aliases: []string{"restart", "r"}, group: runCmds, cmdFn: restart, helpMsg: `Restart process.
 
 For recorded targets the command takes the following forms:
@@ -1664,6 +1679,30 @@ func edit(t *Term, ctx callContext, args string) error {
 	return cmd.Run()
 }
 
+func watchpoint(t *Term, ctx callContext, args string) error {
+	v := strings.SplitN(args, " ", 2)
+	if len(v) != 2 {
+		return errors.New("wrong number of arguments: watch [-r|-w|-rw] <expr>")
+	}
+	var wtype api.WatchType
+	switch v[0] {
+	case "-r":
+		wtype = api.WatchRead
+	case "-w":
+		wtype = api.WatchWrite
+	case "-rw":
+		wtype = api.WatchRead | api.WatchWrite
+	default:
+		return fmt.Errorf("wrong argument %q to watch", v[0])
+	}
+	bp, err := t.client.CreateWatchpoint(ctx.Scope, v[1], wtype)
+	if err != nil {
+		return err
+	}
+	fmt.Printf("%s set at %s\n", formatBreakpointName(bp, true), t.formatBreakpointLocation(bp))
+	return nil
+}
+
 func examineMemoryCmd(t *Term, ctx callContext, argstr string) error {
 	var (
 		address uint64
@@ -2432,7 +2471,9 @@ func printcontextThread(t *Term, th *api.Thread) {
 	}
 
 	bpname := ""
-	if th.Breakpoint.Name != "" {
+	if th.Breakpoint.WatchExpr != "" {
+		bpname = fmt.Sprintf("watchpoint on [%s] ", th.Breakpoint.WatchExpr)
+	} else if th.Breakpoint.Name != "" {
 		bpname = fmt.Sprintf("[%s] ", th.Breakpoint.Name)
 	}
 
@@ -2794,6 +2835,9 @@ func formatBreakpointName(bp *api.Breakpoint, upcase bool) string {
 	if bp.Tracepoint {
 		thing = "tracepoint"
 	}
+	if bp.WatchExpr != "" {
+		thing = "watchpoint"
+	}
 	if upcase {
 		thing = strings.Title(thing)
 	}
@@ -2801,6 +2845,9 @@ func formatBreakpointName(bp *api.Breakpoint, upcase bool) string {
 	if id == "" {
 		id = strconv.Itoa(bp.ID)
 	}
+	if bp.WatchExpr != "" && bp.WatchExpr != bp.Name {
+		return fmt.Sprintf("%s %s on [%s]", thing, id, bp.WatchExpr)
+	}
 	state := "(enabled)"
 	if bp.Disabled {
 		state = "(disabled)"
@@ -2822,11 +2869,13 @@ func (t *Term) formatBreakpointLocation(bp *api.Breakpoint) string {
 		// In case we are connecting to an older version of delve that does not return the Addrs field.
 		fmt.Fprintf(&out, "%#x", bp.Addr)
 	}
-	fmt.Fprintf(&out, " for ")
-	p := t.formatPath(bp.File)
-	if bp.FunctionName != "" {
-		fmt.Fprintf(&out, "%s() ", bp.FunctionName)
+	if bp.WatchExpr == "" {
+		fmt.Fprintf(&out, " for ")
+		p := t.formatPath(bp.File)
+		if bp.FunctionName != "" {
+			fmt.Fprintf(&out, "%s() ", bp.FunctionName)
+		}
+		fmt.Fprintf(&out, "%s:%d", p, bp.Line)
 	}
-	fmt.Fprintf(&out, "%s:%d", p, bp.Line)
 	return out.String()
 }

pkg/terminal/starbind/starlark_mapping.go

@@ -313,6 +313,54 @@ func (env *Env) starlarkPredeclare() starlark.StringDict {
 		}
 		return env.interfaceToStarlarkValue(rpcRet), nil
 	})
+	r["create_watchpoint"] = starlark.NewBuiltin("create_watchpoint", func(thread *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
+		if err := isCancelled(thread); err != nil {
+			return starlark.None, decorateError(thread, err)
+		}
+		var rpcArgs rpc2.CreateWatchpointIn
+		var rpcRet rpc2.CreateWatchpointOut
+		if len(args) > 0 && args[0] != starlark.None {
+			err := unmarshalStarlarkValue(args[0], &rpcArgs.Scope, "Scope")
+			if err != nil {
+				return starlark.None, decorateError(thread, err)
+			}
+		} else {
+			rpcArgs.Scope = env.ctx.Scope()
+		}
+		if len(args) > 1 && args[1] != starlark.None {
+			err := unmarshalStarlarkValue(args[1], &rpcArgs.Expr, "Expr")
+			if err != nil {
+				return starlark.None, decorateError(thread, err)
+			}
+		}
+		if len(args) > 2 && args[2] != starlark.None {
+			err := unmarshalStarlarkValue(args[2], &rpcArgs.Type, "Type")
+			if err != nil {
+				return starlark.None, decorateError(thread, err)
+			}
+		}
+		for _, kv := range kwargs {
+			var err error
+			switch kv[0].(starlark.String) {
+			case "Scope":
+				err = unmarshalStarlarkValue(kv[1], &rpcArgs.Scope, "Scope")
+			case "Expr":
+				err = unmarshalStarlarkValue(kv[1], &rpcArgs.Expr, "Expr")
+			case "Type":
+				err = unmarshalStarlarkValue(kv[1], &rpcArgs.Type, "Type")
+			default:
+				err = fmt.Errorf("unknown argument %q", kv[0])
+			}
+			if err != nil {
+				return starlark.None, decorateError(thread, err)
+			}
+		}
+		err := env.ctx.Client().CallAPI("CreateWatchpoint", &rpcArgs, &rpcRet)
+		if err != nil {
+			return starlark.None, err
+		}
+		return env.interfaceToStarlarkValue(rpcRet), nil
+	})
 	r["detach"] = starlark.NewBuiltin("detach", func(thread *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
 		if err := isCancelled(thread); err != nil {
 			return starlark.None, decorateError(thread, err)

service/api/conversions.go

@@ -33,6 +33,8 @@ func ConvertBreakpoint(bp *proc.Breakpoint) *Breakpoint {
 		Variables:     bp.Variables,
 		LoadArgs:      LoadConfigFromProc(bp.LoadArgs),
 		LoadLocals:    LoadConfigFromProc(bp.LoadLocals),
+		WatchExpr:     bp.WatchExpr,
+		WatchType:     WatchType(bp.WatchType),
 		TotalHitCount: bp.TotalHitCount,
 		Addrs:         []uint64{bp.Addr},
 	}

service/api/types.go

@@ -83,6 +83,11 @@ type Breakpoint struct {
 	LoadArgs *LoadConfig
 	// LoadLocals requests loading function locals when the breakpoint is hit
 	LoadLocals *LoadConfig
+
+	// WatchExpr is the expression used to create this watchpoint
+	WatchExpr string
+	WatchType WatchType
+
 	// number of times a breakpoint has been reached in a certain goroutine
 	HitCount map[string]uint64 `json:"hitCount"`
 	// number of times a breakpoint has been reached
@@ -109,6 +114,14 @@ func ValidBreakpointName(name string) error {
 	return nil
 }
 
+// WatchType is the watchpoint type
+type WatchType uint8
+
+const (
+	WatchRead WatchType = 1 << iota
+	WatchWrite
+)
+
 // Thread is a thread within the debugged process.
 type Thread struct {
 	// ID is a unique identifier for the thread.

service/client.go

@@ -66,6 +66,8 @@ type Client interface {
 	GetBreakpointByName(name string) (*api.Breakpoint, error)
 	// CreateBreakpoint creates a new breakpoint.
 	CreateBreakpoint(*api.Breakpoint) (*api.Breakpoint, error)
+	// CreateWatchpoint creates a new watchpoint.
+	CreateWatchpoint(api.EvalScope, string, api.WatchType) (*api.Breakpoint, error)
 	// ListBreakpoints gets all breakpoints.
 	ListBreakpoints() ([]*api.Breakpoint, error)
 	// ClearBreakpoint deletes a breakpoint by ID.

service/debugger/debugger.go

@@ -517,7 +517,9 @@ func (d *Debugger) Restart(rerecord bool, pos string, resetArgs bool, newArgs []
 		if oldBp.ID > maxID {
 			maxID = oldBp.ID
 		}
-		if len(oldBp.File) > 0 {
+		if oldBp.WatchExpr != "" {
+			discarded = append(discarded, api.DiscardedBreakpoint{Breakpoint: oldBp, Reason: "can not recreate watchpoints on restart"})
+		} else if len(oldBp.File) > 0 {
 			addrs, err := proc.FindFileLocation(p, oldBp.File, oldBp.Line)
 			if err != nil {
 				discarded = append(discarded, api.DiscardedBreakpoint{Breakpoint: oldBp, Reason: err.Error()})
@@ -527,6 +529,7 @@ func (d *Debugger) Restart(rerecord bool, pos string, resetArgs bool, newArgs []
 		} else {
 			// Avoid setting a breakpoint based on address when rebuilding
 			if rebuild {
+				discarded = append(discarded, api.DiscardedBreakpoint{Breakpoint: oldBp, Reason: "can not recreate address breakpoints on restart"})
 				continue
 			}
 			newBp, err := p.SetBreakpointWithID(oldBp.ID, oldBp.Addr)
@@ -730,6 +733,11 @@ func (d *Debugger) AmendBreakpoint(amend *api.Breakpoint) error {
 	defer d.targetMutex.Unlock()
 
 	originals := d.findBreakpoint(amend.ID)
+
+	if len(originals) > 0 && originals[0].WatchExpr != "" && amend.Disabled {
+		return errors.New("can not disable watchpoints")
+	}
+
 	_, disabled := d.disabledBreakpoints[amend.ID]
 	if originals == nil && !disabled {
 		return fmt.Errorf("no breakpoint with ID %d", amend.ID)
@@ -938,6 +946,22 @@ func (d *Debugger) findDisabledBreakpointByName(name string) *api.Breakpoint {
 	return nil
 }
 
+// CreateWatchpoint creates a watchpoint on the specified expression.
+func (d *Debugger) CreateWatchpoint(goid, frame, deferredCall int, expr string, wtype api.WatchType) (*api.Breakpoint, error) {
+	s, err := proc.ConvertEvalScope(d.target, goid, frame, deferredCall)
+	if err != nil {
+		return nil, err
+	}
+	bp, err := d.target.SetWatchpoint(s, expr, proc.WatchType(wtype), nil)
+	if err != nil {
+		return nil, err
+	}
+	if api.ValidBreakpointName(expr) == nil && d.findBreakpointByName(expr) == nil {
+		bp.Name = expr
+	}
+	return api.ConvertBreakpoint(bp), nil
+}
+
 // Threads returns the threads of the target process.
 func (d *Debugger) Threads() ([]proc.Thread, error) {
 	d.targetMutex.Lock()
@@ -1889,6 +1913,9 @@ func (v breakpointsByLogicalID) Swap(i, j int) { v[i], v[j] = v[j], v[i] }
 
 func (v breakpointsByLogicalID) Less(i, j int) bool {
 	if v[i].LogicalID == v[j].LogicalID {
+		if v[i].WatchType != v[j].WatchType {
+			return v[i].WatchType > v[j].WatchType // if a logical breakpoint contains a watchpoint let the watchpoint sort first
+		}
 		return v[i].Addr < v[j].Addr
 	}
 	return v[i].LogicalID < v[j].LogicalID

service/rpc2/client.go

@@ -232,6 +232,12 @@ func (c *RPCClient) CreateBreakpoint(breakPoint *api.Breakpoint) (*api.Breakpoin
 	return &out.Breakpoint, err
 }
 
+func (c *RPCClient) CreateWatchpoint(scope api.EvalScope, expr string, wtype api.WatchType) (*api.Breakpoint, error) {
+	var out CreateWatchpointOut
+	err := c.call("CreateWatchpoint", CreateWatchpointIn{scope, expr, wtype}, &out)
+	return out.Breakpoint, err
+}
+
 func (c *RPCClient) ListBreakpoints() ([]*api.Breakpoint, error) {
 	var out ListBreakpointsOut
 	err := c.call("ListBreakpoints", ListBreakpointsIn{}, &out)

service/rpc2/server.go

@@ -939,3 +939,19 @@ type DumpCancelOut struct {
 func (s *RPCServer) DumpCancel(arg DumpCancelIn, out *DumpCancelOut) error {
 	return s.debugger.DumpCancel()
 }
+
+type CreateWatchpointIn struct {
+	Scope api.EvalScope
+	Expr  string
+	Type  api.WatchType
+}
+
+type CreateWatchpointOut struct {
+	*api.Breakpoint
+}
+
+func (s *RPCServer) CreateWatchpoint(arg CreateWatchpointIn, out *CreateWatchpointOut) error {
+	var err error
+	out.Breakpoint, err = s.debugger.CreateWatchpoint(arg.Scope.GoroutineID, arg.Scope.Frame, arg.Scope.DeferredCall, arg.Expr, arg.Type)
+	return err
+}