Abandon lazily calling runtime.CallersFrames.

Although the idea is attractive, Go 1.9 deprecated the ability to
reliably use slices of the []uintptr returned from runtime.Callers.
It is difficult to implement the CallStack Trim methods without
being able to subslice or reverse iterate the []uintptr.

Author: ChrisHines

.travis.yml

@@ -1,16 +1,13 @@
 language: go
 sudo: false
 go:
-  - 1.2
-  - 1.3
-  - 1.4
-  - 1.5
-  - 1.6
+  - 1.7
+  - 1.8
+  - 1.9
   - tip
 
 before_install:
   - go get github.com/mattn/goveralls
-  - go get golang.org/x/tools/cmd/cover
 
 script:
   - goveralls -service=travis-ci

stack.go

@@ -1,3 +1,5 @@
+// +build go1.7
+
 // Package stack implements utilities to capture, manipulate, and format call
 // stacks. It provides a simpler API than package runtime.
 //
@@ -21,23 +23,31 @@ import (
 
 // Call records a single function invocation from a goroutine stack.
 type Call struct {
-	pcs [2]uintptr
+	frame runtime.Frame
 }
 
 // Caller returns a Call from the stack of the current goroutine. The argument
 // skip is the number of stack frames to ascend, with 0 identifying the
 // calling function.
 func Caller(skip int) Call {
-	var pcs [2]uintptr
+	// As of Go 1.9 we need room for up to three PC entries.
+	//
+	// 0. An entry for the stack frame prior to the target to check for
+	//    special handling needed if that prior entry is runtime.sigpanic.
+	// 1. A possible second entry to hold metadata about skipped inlined
+	//    functions. If inline functions were not skipped the target frame
+	//    PC will be here.
+	// 2. A third entry for the target frame PC when the second entry
+	//    is used for skipped inline functions.
+	var pcs [3]uintptr
 	n := runtime.Callers(skip+1, pcs[:])
+	frames := runtime.CallersFrames(pcs[:n])
+	frame, _ := frames.Next()
+	frame, _ = frames.Next()
 
-	var c Call
-	if n < 2 {
-		return c
+	return Call{
+		frame: frame,
 	}
-
-	c.pcs = pcs
-	return c
 }
 
 // String implements fmt.Stinger. It is equivalent to fmt.Sprintf("%v", c).
@@ -48,7 +58,7 @@ func (c Call) String() string {
 // MarshalText implements encoding.TextMarshaler. It formats the Call the same
 // as fmt.Sprintf("%v", c).
 func (c Call) MarshalText() ([]byte, error) {
-	if c.pcs[0] == 0 {
+	if c.frame == (runtime.Frame{}) {
 		return nil, ErrNoFunc
 	}
 
@@ -78,31 +88,19 @@ var ErrNoFunc = errors.New("no call stack information")
 //    %+v   equivalent to %+s:%d
 //    %#v   equivalent to %#s:%d
 func (c Call) Format(s fmt.State, verb rune) {
-	frames := runtime.CallersFrames(c.pcs[:])
-	head, _ := frames.Next()
-	frame, _ := frames.Next()
-
-	if head.Function == "runtime.signpanic" {
-		frame, _ = frames.Next()
-	}
-
-	format(&frame, s, verb)
-}
-
-func format(frame *runtime.Frame, s fmt.State, verb rune) {
-	if frame.Func == nil {
+	if c.frame == (runtime.Frame{}) {
 		fmt.Fprintf(s, "%%!%c(NOFUNC)", verb)
 		return
 	}
 
 	switch verb {
 	case 's', 'v':
-		file, line := frame.File, frame.Line
+		file := c.frame.File
 		switch {
 		case s.Flag('#'):
 			// done
 		case s.Flag('+'):
-			file = file[pkgIndex(file, frame.Function):]
+			file = file[pkgIndex(file, c.frame.Function):]
 		default:
 			const sep = "/"
 			if i := strings.LastIndex(file, sep); i != -1 {
@@ -112,16 +110,15 @@ func format(frame *runtime.Frame, s fmt.State, verb rune) {
 		io.WriteString(s, file)
 		if verb == 'v' {
 			buf := [7]byte{':'}
-			s.Write(strconv.AppendInt(buf[:1], int64(line), 10))
+			s.Write(strconv.AppendInt(buf[:1], int64(c.frame.Line), 10))
 		}
 
 	case 'd':
-		line := frame.Line
 		buf := [6]byte{}
-		s.Write(strconv.AppendInt(buf[:0], int64(line), 10))
+		s.Write(strconv.AppendInt(buf[:0], int64(c.frame.Line), 10))
 
 	case 'k':
-		name := frame.Function
+		name := c.frame.Function
 		const pathSep = "/"
 		start, end := 0, len(name)
 		if i := strings.LastIndex(name, pathSep); i != -1 {
@@ -137,7 +134,7 @@ func format(frame *runtime.Frame, s fmt.State, verb rune) {
 		io.WriteString(s, name[start:end])
 
 	case 'n':
-		name := frame.Function
+		name := c.frame.Function
 		if !s.Flag('+') {
 			const pathSep = "/"
 			if i := strings.LastIndex(name, pathSep); i != -1 {
@@ -152,43 +149,17 @@ func format(frame *runtime.Frame, s fmt.State, verb rune) {
 	}
 }
 
+// Frame returns the call frame infomation for the Call.
+func (c Call) Frame() runtime.Frame {
+	return c.frame
+}
+
 // PC returns the program counter for this call frame; multiple frames may
 // have the same PC value.
+//
+// Deprecated: Use Call.Frame instead.
 func (c Call) PC() uintptr {
-	return c.pcs[1]
-}
-
-func (c Call) frame() *runtime.Frame {
-	frames := runtime.CallersFrames(c.pcs[:])
-	frame, _ := frames.Next()
-	frame, _ = frames.Next()
-	return &frame
-}
-
-// name returns the import path qualified name of the function containing the
-// call.
-func (c Call) name() string {
-	frame := c.frame()
-	if frame.Func == nil {
-		return "???"
-	}
-	return frame.Function
-}
-
-func (c Call) file() string {
-	frame := c.frame()
-	if frame.Func == nil {
-		return "???"
-	}
-	return frame.File
-}
-
-func (c Call) line() int {
-	frame := c.frame()
-	if frame.Func == nil {
-		return 0
-	}
-	return frame.Line
+	return c.frame.PC
 }
 
 // CallStack records a sequence of function invocations from a goroutine
@@ -226,31 +197,12 @@ func (cs CallStack) MarshalText() ([]byte, error) {
 // supplied verb and options.
 func (cs CallStack) Format(s fmt.State, verb rune) {
 	s.Write(openBracketBytes)
-
-	var pcs []uintptr
-	for _, c := range cs {
-		pcs = append(pcs, c.pcs[:]...)
-	}
-
-	frames := runtime.CallersFrames(pcs[:])
-
-	initial := true
-	for frame, more := frames.Next(); more; frame, more = frames.Next() {
-		if !initial {
+	for i, pc := range cs {
+		if i > 0 {
 			s.Write(spaceBytes)
 		}
-
-		next, _ := frames.Next()
-		if frame.Function == "runtime.sigpanic" {
-			frame, _ = runtime.CallersFrames([]uintptr{next.PC - 1}).Next()
-		} else {
-			frame = next
-		}
-
-		format(&frame, s, verb)
-		initial = false
+		pc.Format(s, verb)
 	}
-
 	s.Write(closeBracketBytes)
 }
 
@@ -259,12 +211,17 @@ func (cs CallStack) Format(s fmt.State, verb rune) {
 func Trace() CallStack {
 	var pcs [512]uintptr
 	n := runtime.Callers(1, pcs[:])
-	cs := make([]Call, n)
 
-	for i := range pcs[:n] {
-		cs[i] = Call{
-			pcs: [2]uintptr{pcs[i], pcs[i+1]},
-		}
+	frames := runtime.CallersFrames(pcs[:n])
+	cs := make(CallStack, 0, n)
+
+	// Skip extra frame retrieved just to make sure the runtime.sigpanic
+	// special case is handled.
+	frame, more := frames.Next()
+
+	for more {
+		frame, more = frames.Next()
+		cs = append(cs, Call{frame: frame})
 	}
 
 	return cs
@@ -273,7 +230,7 @@ func Trace() CallStack {
 // TrimBelow returns a slice of the CallStack with all entries below c
 // removed.
 func (cs CallStack) TrimBelow(c Call) CallStack {
-	for len(cs) > 0 && cs[0].pcs[1] != c.pcs[1] {
+	for len(cs) > 0 && cs[0] != c {
 		cs = cs[1:]
 	}
 	return cs
@@ -282,7 +239,7 @@ func (cs CallStack) TrimBelow(c Call) CallStack {
 // TrimAbove returns a slice of the CallStack with all entries above c
 // removed.
 func (cs CallStack) TrimAbove(c Call) CallStack {
-	for len(cs) > 0 && cs[len(cs)-1].pcs[1] != c.pcs[1] {
+	for len(cs) > 0 && cs[len(cs)-1] != c {
 		cs = cs[:len(cs)-1]
 	}
 	return cs
@@ -331,12 +288,13 @@ func pkgIndex(file, funcName string) int {
 var runtimePath string
 
 func init() {
-	var pcs [1]uintptr
+	var pcs [3]uintptr
 	runtime.Callers(0, pcs[:])
-	fn := runtime.FuncForPC(pcs[0])
-	file, _ := fn.FileLine(pcs[0])
+	frames := runtime.CallersFrames(pcs[:])
+	frame, _ := frames.Next()
+	file := frame.File
 
-	idx := pkgIndex(file, fn.Name())
+	idx := pkgIndex(frame.File, frame.Function)
 
 	runtimePath = file[:idx]
 	if runtime.GOOS == "windows" {
@@ -345,7 +303,7 @@ func init() {
 }
 
 func inGoroot(c Call) bool {
-	file := c.file()
+	file := c.frame.File
 	if len(file) == 0 || file[0] == '?' {
 		return true
 	}

stack_test.go

@@ -17,9 +17,9 @@ const importPath = "github.com/go-stack/stack"
 
 type testType struct{}
 
-func (tt testType) testMethod() (c stack.Call, pc uintptr, file string, line int, ok bool) {
+func (tt testType) testMethod() (c stack.Call, file string, line int, ok bool) {
 	c = stack.Caller(0)
-	pc, file, line, ok = runtime.Caller(0)
+	_, file, line, ok = runtime.Caller(0)
 	line--
 	return
 }
@@ -28,14 +28,14 @@ func TestCallFormat(t *testing.T) {
 	t.Parallel()
 
 	c := stack.Caller(0)
-	pc, file, line, ok := runtime.Caller(0)
+	_, file, line, ok := runtime.Caller(0)
 	line--
 	if !ok {
 		t.Fatal("runtime.Caller(0) failed")
 	}
 	relFile := path.Join(importPath, filepath.Base(file))
 
-	c2, pc2, file2, line2, ok2 := testType{}.testMethod()
+	c2, file2, line2, ok2 := testType{}.testMethod()
 	if !ok2 {
 		t.Fatal("runtime.Caller(0) failed")
 	}
@@ -54,7 +54,7 @@ func TestCallFormat(t *testing.T) {
 		{c, "func", "%#s", file},
 		{c, "func", "%d", fmt.Sprint(line)},
 		{c, "func", "%n", "TestCallFormat"},
-		{c, "func", "%+n", runtime.FuncForPC(pc - 1).Name()},
+		{c, "func", "%+n", "github.com/go-stack/stack_test.TestCallFormat"},
 		{c, "func", "%k", "stack_test"},
 		{c, "func", "%+k", "github.com/go-stack/stack_test"},
 		{c, "func", "%v", fmt.Sprint(path.Base(file), ":", line)},
@@ -66,7 +66,7 @@ func TestCallFormat(t *testing.T) {
 		{c2, "meth", "%#s", file2},
 		{c2, "meth", "%d", fmt.Sprint(line2)},
 		{c2, "meth", "%n", "testType.testMethod"},
-		{c2, "meth", "%+n", runtime.FuncForPC(pc2).Name()},
+		{c2, "meth", "%+n", "github.com/go-stack/stack_test.testType.testMethod"},
 		{c2, "meth", "%k", "stack_test"},
 		{c2, "meth", "%+k", "github.com/go-stack/stack_test"},
 		{c2, "meth", "%v", fmt.Sprint(path.Base(file2), ":", line2)},
@@ -92,7 +92,7 @@ func TestCallString(t *testing.T) {
 		t.Fatal("runtime.Caller(0) failed")
 	}
 
-	c2, _, file2, line2, ok2 := testType{}.testMethod()
+	c2, file2, line2, ok2 := testType{}.testMethod()
 	if !ok2 {
 		t.Fatal("runtime.Caller(0) failed")
 	}
@@ -125,7 +125,7 @@ func TestCallMarshalText(t *testing.T) {
 		t.Fatal("runtime.Caller(0) failed")
 	}
 
-	c2, _, file2, line2, ok2 := testType{}.testMethod()
+	c2, file2, line2, ok2 := testType{}.testMethod()
 	if !ok2 {
 		t.Fatal("runtime.Caller(0) failed")
 	}
@@ -191,7 +191,7 @@ func getTrace(t *testing.T) (stack.CallStack, int) {
 func TestTrimAbove(t *testing.T) {
 	trace := trimAbove()
 	if got, want := len(trace), 2; got != want {
-		t.Errorf("got len(trace) == %v, want %v, trace: %n", got, want, trace)
+		t.Fatalf("got len(trace) == %v, want %v, trace: %n", got, want, trace)
 	}
 	if got, want := fmt.Sprintf("%n", trace[1]), "TestTrimAbove"; got != want {
 		t.Errorf("got %q, want %q", got, want)
@@ -224,8 +224,6 @@ func TestTrimRuntime(t *testing.T) {
 	}
 }
 
-
-
 func BenchmarkCallVFmt(b *testing.B) {
 	c := stack.Caller(0)
 	b.ResetTimer()