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jeremybenn |
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package debug contains facilities for programs to debug themselves while
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// they are running.
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package debug
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import (
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"bytes"
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"fmt"
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"io/ioutil"
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"os"
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"runtime"
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)
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var (
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dunno = []byte("???")
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centerDot = []byte("·")
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dot = []byte(".")
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)
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// PrintStack prints to standard error the stack trace returned by Stack.
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func PrintStack() {
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os.Stderr.Write(stack())
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}
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// Stack returns a formatted stack trace of the goroutine that calls it.
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// For each routine, it includes the source line information and PC value,
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// then attempts to discover, for Go functions, the calling function or
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// method and the text of the line containing the invocation.
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func Stack() []byte {
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return stack()
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}
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// stack implements Stack, skipping 2 frames
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func stack() []byte {
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buf := new(bytes.Buffer) // the returned data
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// As we loop, we open files and read them. These variables record the currently
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// loaded file.
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var lines [][]byte
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var lastFile string
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for i := 2; ; i++ { // Caller we care about is the user, 2 frames up
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pc, file, line, ok := runtime.Caller(i)
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if !ok {
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break
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}
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// Print this much at least. If we can't find the source, it won't show.
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fmt.Fprintf(buf, "%s:%d (0x%x)\n", file, line, pc)
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if file != lastFile {
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data, err := ioutil.ReadFile(file)
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if err != nil {
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continue
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}
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lines = bytes.Split(data, []byte{'\n'})
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lastFile = file
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}
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line-- // in stack trace, lines are 1-indexed but our array is 0-indexed
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fmt.Fprintf(buf, "\t%s: %s\n", function(pc), source(lines, line))
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}
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return buf.Bytes()
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}
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// source returns a space-trimmed slice of the n'th line.
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func source(lines [][]byte, n int) []byte {
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if n < 0 || n >= len(lines) {
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return dunno
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}
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return bytes.Trim(lines[n], " \t")
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}
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// function returns, if possible, the name of the function containing the PC.
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func function(pc uintptr) []byte {
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fn := runtime.FuncForPC(pc)
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if fn == nil {
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return dunno
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}
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name := []byte(fn.Name())
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// The name includes the path name to the package, which is unnecessary
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// since the file name is already included. Plus, it has center dots.
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// That is, we see
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// runtime/debug.*T·ptrmethod
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// and want
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// *T.ptrmethod
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if period := bytes.Index(name, dot); period >= 0 {
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name = name[period+1:]
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}
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name = bytes.Replace(name, centerDot, dot, -1)
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return name
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}
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