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// Copyright 2019 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
package log
import (
var (
unknown = []byte("???")
// Stack will skip back the provided number of frames and return a stack trace with source code.
// Although we could just use debug.Stack(), this routine will return the source code and
// skip back the provided number of frames - i.e. allowing us to ignore preceding function calls.
// A skip of 0 returns the stack trace for the calling function, not including this call.
// If the problem is a lack of memory of course all this is not going to work...
func Stack(skip int) string {
buf := new(bytes.Buffer)
// Store the last file we opened as its probable that the preceding stack frame
// will be in the same file
var lines [][]byte
var lastFilename string
for i := skip + 1; ; i++ { // Skip over frames
programCounter, filename, lineNumber, ok := runtime.Caller(i)
// If we can't retrieve the information break - basically we're into go internals at this point.
if !ok {
// Print equivalent of debug.Stack()
fmt.Fprintf(buf, "%s:%d (0x%x)\n", filename, lineNumber, programCounter)
// Now try to print the offending line
if filename != lastFilename {
data, err := ioutil.ReadFile(filename)
if err != nil {
// can't read this sourcefile
// likely we don't have the sourcecode available
lines = bytes.Split(data, []byte{'\n'})
lastFilename = filename
fmt.Fprintf(buf, "\t%s: %s\n", functionName(programCounter), source(lines, lineNumber))
return buf.String()
// functionName converts the provided programCounter into a function name
func functionName(programCounter uintptr) []byte {
function := runtime.FuncForPC(programCounter)
if function == nil {
return unknown
name := []byte(function.Name())
// Because we provide the filename we can drop the preceding package name.
if lastslash := bytes.LastIndex(name, []byte("/")); lastslash >= 0 {
name = name[lastslash+1:]
// And the current package name.
if period := bytes.Index(name, []byte(".")); period >= 0 {
name = name[period+1:]
// And we should just replace the interpunct with a dot
name = bytes.Replace(name, []byte("·"), []byte("."), -1)
return name
// source returns a space-trimmed slice of the n'th line.
func source(lines [][]byte, n int) []byte {
n-- // in stack trace, lines are 1-indexed but our array is 0-indexed
if n < 0 || n >= len(lines) {
return unknown
return bytes.TrimSpace(lines[n])