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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// The debug package contains facilities for programs to debug themselves
// while they are running.
package debug
import (
"bytes"
"fmt"
"io/ioutil"
"os"
"runtime"
)
var (
dunno = []byte("???")
centerDot = []byte("·")
dot = []byte(".")
)
// PrintStack prints to standard error the stack trace returned by Stack.
func PrintStack() {
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.
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
}
// 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'}, -1)
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
if period := bytes.Index(name, dot); period >= 0 {
name = name[period+1:]
}
name = bytes.Replace(name, centerDot, dot, -1)
return name
}
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