// 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. // Package debug contains facilities for programs to debug themselves while // they are running. package debug import ( "bytes" _ "debug/elf" "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'}) 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 }