runtime/debug: implement Stack using runtime.Stack

Fixes #12363

Change-Id: I1a025ab6a1cbd5a58f5c2bce5416788387495428
Reviewed-on: https://go-review.googlesource.com/14604
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 8 insertions, 74 deletions

diff --git a/src/runtime/debug/stack.go b/src/runtime/debug/stack.go
index ab12bffa6e..952d834bc4 100644
--- a/src/runtime/debug/stack.go
+++ b/src/runtime/debug/stack.go
@@ -7,92 +7,26 @@
 package debug
 
 import (
-	"bytes"
-	"fmt"
-	"io/ioutil"
 	"os"
 	"runtime"
 )
 
-var (
-	dunno     = []byte("???")
-	centerDot = []byte("·")
-	dot       = []byte(".")
-	slash     = []byte("/")
-)
-
 // PrintStack prints to standard error the stack trace returned by Stack.
 func PrintStack() {
-	os.Stderr.Write(stack())
+	os.Stderr.Write(Stack())
 }
 
 // Stack returns a formatted stack trace of the goroutine that calls it.
 // For each routine, it includes the source line information and PC value,
 // then attempts to discover, for Go functions, the calling function or
-// method and the text of the line containing the invocation.
-//
-// Deprecated: Use package runtime's Stack instead.
+// method.
 func Stack() []byte {
-	return stack()
-}
-
-// stack implements Stack, skipping 2 frames
-func stack() []byte {
-	buf := new(bytes.Buffer) // the returned data
-	// As we loop, we open files and read them. These variables record the currently
-	// loaded file.
-	var lines [][]byte
-	var lastFile string
-	for i := 2; ; i++ { // Caller we care about is the user, 2 frames up
-		pc, file, line, ok := runtime.Caller(i)
-		if !ok {
-			break
+	buf := make([]byte, 1024)
+	for {
+		n := runtime.Stack(buf, false)
+		if n < len(buf) {
+			return buf[:n]
 		}
-		// Print this much at least.  If we can't find the source, it won't show.
-		fmt.Fprintf(buf, "%s:%d (0x%x)\n", file, line, pc)
-		if file != lastFile {
-			data, err := ioutil.ReadFile(file)
-			if err != nil {
-				continue
-			}
-			lines = bytes.Split(data, []byte{'\n'})
-			lastFile = file
-		}
-		line-- // in stack trace, lines are 1-indexed but our array is 0-indexed
-		fmt.Fprintf(buf, "\t%s: %s\n", function(pc), source(lines, line))
-	}
-	return buf.Bytes()
-}
-
-// source returns a space-trimmed slice of the n'th line.
-func source(lines [][]byte, n int) []byte {
-	if n < 0 || n >= len(lines) {
-		return dunno
-	}
-	return bytes.Trim(lines[n], " \t")
-}
-
-// function returns, if possible, the name of the function containing the PC.
-func function(pc uintptr) []byte {
-	fn := runtime.FuncForPC(pc)
-	if fn == nil {
-		return dunno
-	}
-	name := []byte(fn.Name())
-	// The name includes the path name to the package, which is unnecessary
-	// since the file name is already included.  Plus, it has center dots.
-	// That is, we see
-	//	runtime/debug.*T·ptrmethod
-	// and want
-	//	*T.ptrmethod
-	// Since the package path might contains dots (e.g. code.google.com/...),
-	// we first remove the path prefix if there is one.
-	if lastslash := bytes.LastIndex(name, slash); lastslash >= 0 {
-		name = name[lastslash+1:]
-	}
-	if period := bytes.Index(name, dot); period >= 0 {
-		name = name[period+1:]
+		buf = make([]byte, 2*len(buf))
 	}
-	name = bytes.Replace(name, centerDot, dot, -1)
-	return name
 }