proc: step now goes to next line, including funcs

This patch modifies the `step` command to step to the next source line,
stepping into any function encountered along the way.

Fixes #360

_fixtures/teststep.go

+package main
+
+import (
+	"fmt"
+	"runtime"
+)
+
+func callme() {
+	fmt.Println("hi")
+}
+
+func main() {
+	runtime.Breakpoint()
+	callme()
+}

proc/proc.go

@@ -220,6 +220,11 @@ func (dbp *Process) FunctionEntryToFirstLine(entry uint64) (uint64, error) {
 	return entry, nil
 }
 
+// CurrentLocation returns the location of the current thread.
+func (dbp *Process) CurrentLocation() (*Location, error) {
+	return dbp.CurrentThread.Location()
+}
+
 // RequestManualStop sets the `halt` flag and
 // sends SIGSTOP to all threads.
 func (dbp *Process) RequestManualStop() error {
@@ -381,7 +386,7 @@ func (dbp *Process) Continue() error {
 			// runtime.Breakpoint or manual stop
 			if dbp.CurrentThread.onRuntimeBreakpoint() {
 				for i := 0; i < 2; i++ {
-					if err = dbp.CurrentThread.Step(); err != nil {
+					if err = dbp.CurrentThread.StepInstruction(); err != nil {
 						return err
 					}
 				}
@@ -446,18 +451,48 @@ func (dbp *Process) pickCurrentThread(trapthread *Thread) error {
 	return dbp.SwitchThread(trapthread.ID)
 }
 
-// Step will continue the current thread for exactly
+// Step will continue until another source line is reached.
+// Will step into functions.
+func (dbp *Process) Step() (err error) {
+	fn := func() error {
+		var nloc *Location
+		th := dbp.CurrentThread
+		loc, err := th.Location()
+		if err != nil {
+			return err
+		}
+		for {
+			err = dbp.CurrentThread.singleStep()
+			if err != nil {
+				return err
+			}
+			nloc, err = th.Location()
+			if err != nil {
+				return err
+			}
+			if nloc.File != loc.File {
+				return nil
+			}
+			if nloc.File == loc.File && nloc.Line != loc.Line {
+				return nil
+			}
+		}
+	}
+	return dbp.run(fn)
+}
+
+// StepInstruction will continue the current thread for exactly
 // one instruction. This method affects only the thread
 // asssociated with the selected goroutine. All other
 // threads will remain stopped.
-func (dbp *Process) Step() (err error) {
+func (dbp *Process) StepInstruction() (err error) {
 	if dbp.SelectedGoroutine == nil {
 		return errors.New("cannot single step: no selected goroutine")
 	}
 	if dbp.SelectedGoroutine.thread == nil {
 		return fmt.Errorf("cannot single step: no thread associated with goroutine %d", dbp.SelectedGoroutine.ID)
 	}
-	return dbp.run(dbp.SelectedGoroutine.thread.Step)
+	return dbp.run(dbp.SelectedGoroutine.thread.StepInstruction)
 }
 
 // SwitchThread changes from current thread to the thread specified by `tid`.

proc/proc_darwin.go

@@ -396,7 +396,7 @@ func (dbp *Process) resume() error {
 	// all threads stopped over a breakpoint are made to step over it
 	for _, thread := range dbp.Threads {
 		if thread.CurrentBreakpoint != nil {
-			if err := thread.Step(); err != nil {
+			if err := thread.StepInstruction(); err != nil {
 				return err
 			}
 			thread.CurrentBreakpoint = nil

proc/proc_linux.go

@@ -417,7 +417,7 @@ func (dbp *Process) resume() error {
 	// all threads stopped over a breakpoint are made to step over it
 	for _, thread := range dbp.Threads {
 		if thread.CurrentBreakpoint != nil {
-			if err := thread.Step(); err != nil {
+			if err := thread.StepInstruction(); err != nil {
 				return err
 			}
 			thread.CurrentBreakpoint = nil

proc/proc_test.go

@@ -177,7 +177,7 @@ func TestStep(t *testing.T) {
 		regs := getRegisters(p, t)
 		rip := regs.PC()
 
-		err = p.Step()
+		err = p.CurrentThread.StepInstruction()
 		assertNoError(err, t, "Step()")
 
 		regs = getRegisters(p, t)
@@ -1438,3 +1438,27 @@ func TestIssue356(t *testing.T) {
 		}
 	})
 }
+
+func TestStepIntoFunction(t *testing.T) {
+	withTestProcess("teststep", t, func(p *Process, fixture protest.Fixture) {
+		// Continue until breakpoint
+		assertNoError(p.Continue(), t, "Continue() returned an error")
+		// Step into function
+		assertNoError(p.Step(), t, "Step() returned an error")
+		// We should now be inside the function.
+		loc, err := p.CurrentLocation()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if loc.Fn.Name != "main.callme" {
+			t.Fatalf("expected to be within the 'callme' function, was in %s instead", loc.Fn.Name)
+		}
+		if !strings.Contains(loc.File, "teststep") {
+			t.Fatalf("debugger stopped at incorrect location: %s:%d", loc.File, loc.Line)
+		}
+		// TODO(derekparker) consider skipping function prologue when stepping into func.
+		if loc.Line != 8 {
+			t.Fatalf("debugger stopped at incorrect line: %d", loc.Line)
+		}
+	})
+}

proc/proc_windows.go

@@ -461,7 +461,7 @@ func (dbp *Process) resume() error {
 	thread := dbp.Threads[dbp.os.breakThread]
 	// This relies on the same assumptions as dbp.setCurrentBreakpoints
 	if thread.CurrentBreakpoint != nil {
-		if err := thread.Step(); err != nil {
+		if err := thread.StepInstruction(); err != nil {
 			return err
 		}
 		thread.CurrentBreakpoint = nil

proc/threads.go

@@ -4,11 +4,12 @@ import (
 	"debug/gosym"
 	"encoding/binary"
 	"fmt"
-	"golang.org/x/debug/dwarf"
 	"path/filepath"
 	"reflect"
 	"runtime"
 
+	"golang.org/x/debug/dwarf"
+
 	"github.com/derekparker/delve/dwarf/frame"
 )
 
@@ -53,20 +54,20 @@ func (thread *Thread) Continue() error {
 	// Check whether we are stopped at a breakpoint, and
 	// if so, single step over it before continuing.
 	if _, ok := thread.dbp.FindBreakpoint(pc); ok {
-		if err := thread.Step(); err != nil {
+		if err := thread.StepInstruction(); err != nil {
 			return err
 		}
 	}
 	return thread.resume()
 }
 
-// Step a single instruction.
+// StepInstruction steps a single instruction.
 //
 // Executes exactly one instruction and then returns.
 // If the thread is at a breakpoint, we first clear it,
 // execute the instruction, and then replace the breakpoint.
 // Otherwise we simply execute the next instruction.
-func (thread *Thread) Step() (err error) {
+func (thread *Thread) StepInstruction() (err error) {
 	thread.running = true
 	thread.singleStepping = true
 	defer func() {

service/api/types.go

@@ -184,8 +184,10 @@ type EvalScope struct {
 const (
 	// Continue resumes process execution.
 	Continue = "continue"
-	// Step continues for a single instruction, entering function calls.
+	// Step continues to next source line, entering function calls.
 	Step = "step"
+	// SingleStep continues for exactly 1 cpu instruction.
+	StepInstruction = "stepInstruction"
 	// Next continues to the next source line, not entering function calls.
 	Next = "next"
 	// SwitchThread switches the debugger's current thread context.

service/client.go

@@ -25,6 +25,8 @@ type Client interface {
 	Next() (*api.DebuggerState, error)
 	// Step continues to the next source line, entering function calls.
 	Step() (*api.DebuggerState, error)
+	// SingleStep will step a single cpu instruction.
+	StepInstruction() (*api.DebuggerState, error)
 	// SwitchThread switches the current thread context.
 	SwitchThread(threadID int) (*api.DebuggerState, error)
 	// SwitchGoroutine switches the current goroutine (and the current thread as well)

service/debugger/debugger.go

@@ -261,6 +261,9 @@ func (d *Debugger) Command(command *api.DebuggerCommand) (*api.DebuggerState, er
 	case api.Step:
 		log.Print("stepping")
 		err = d.process.Step()
+	case api.StepInstruction:
+		log.Print("single stepping")
+		err = d.process.StepInstruction()
 	case api.SwitchThread:
 		log.Printf("switching to thread %d", command.ThreadID)
 		err = d.process.SwitchThread(command.ThreadID)

service/rpc/client.go

@@ -101,6 +101,12 @@ func (c *RPCClient) Step() (*api.DebuggerState, error) {
 	return state, err
 }
 
+func (c *RPCClient) StepInstruction() (*api.DebuggerState, error) {
+	state := new(api.DebuggerState)
+	err := c.call("Command", &api.DebuggerCommand{Name: api.StepInstruction}, state)
+	return state, err
+}
+
 func (c *RPCClient) SwitchThread(threadID int) (*api.DebuggerState, error) {
 	state := new(api.DebuggerState)
 	cmd := &api.DebuggerCommand{

terminal/command.go

@@ -60,7 +60,8 @@ func DebugCommands(client service.Client) *Commands {
 		{aliases: []string{"trace", "t"}, cmdFn: tracepoint, helpMsg: "Set tracepoint, takes the same arguments as break."},
 		{aliases: []string{"restart", "r"}, cmdFn: restart, helpMsg: "Restart process."},
 		{aliases: []string{"continue", "c"}, cmdFn: cont, helpMsg: "Run until breakpoint or program termination."},
-		{aliases: []string{"step", "si"}, cmdFn: step, helpMsg: "Single step through program."},
+		{aliases: []string{"step", "s"}, cmdFn: step, helpMsg: "Single step through program."},
+		{aliases: []string{"step-instruction", "si"}, cmdFn: stepInstruction, helpMsg: "Single step a single cpu instruction."},
 		{aliases: []string{"next", "n"}, cmdFn: next, helpMsg: "Step over to next source line."},
 		{aliases: []string{"threads"}, cmdFn: threads, helpMsg: "Print out info for every traced thread."},
 		{aliases: []string{"thread", "tr"}, cmdFn: thread, helpMsg: "Switch to the specified thread."},
@@ -471,6 +472,15 @@ func step(t *Term, args string) error {
 	return nil
 }
 
+func stepInstruction(t *Term, args string) error {
+	state, err := t.client.StepInstruction()
+	if err != nil {
+		return err
+	}
+	printcontext(t, state)
+	return nil
+}
+
 func next(t *Term, args string) error {
 	state, err := t.client.Next()
 	if err != nil {