init

2019-08-08 17:13:34 +08:00
parent e8e5966a8c
commit f0bf2d5fec
2885 changed files with 1195993 additions and 12 deletions
@@ -0,0 +1,750 @@
+// Copyright 2018 Marc-Antoine Ruel. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package stack
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"os/user"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// Context is a parsing context.
+//
+// It contains the deduced GOROOT and GOPATH, if guesspaths is true.
+type Context struct {
+	// Goroutines is the Goroutines found.
+	//
+	// They are in the order that they were printed.
+	Goroutines []*Goroutine
+
+	// GOROOT is the GOROOT as detected in the traceback, not the on the host.
+	//
+	// It can be empty if no root was determined, for example the traceback
+	// contains only non-stdlib source references.
+	//
+	// Empty is guesspaths was false.
+	GOROOT string
+	// GOPATHs is the GOPATH as detected in the traceback, with the value being
+	// the corresponding path mapped to the host.
+	//
+	// It can be empty if only stdlib code is in the traceback or if no local
+	// sources were matched up. In the general case there is only one entry in
+	// the map.
+	//
+	// Nil is guesspaths was false.
+	GOPATHs map[string]string
+
+	localgoroot  string
+	localgopaths []string
+}
+
+// ParseDump processes the output from runtime.Stack().
+//
+// Returns nil *Context if no stack trace was detected.
+//
+// It pipes anything not detected as a panic stack trace from r into out. It
+// assumes there is junk before the actual stack trace. The junk is streamed to
+// out.
+//
+// If guesspaths is false, no guessing of GOROOT and GOPATH is done, and Call
+// entites do not have LocalSrcPath and IsStdlib filled in.
+func ParseDump(r io.Reader, out io.Writer, guesspaths bool) (*Context, error) {
+	goroutines, err := parseDump(r, out)
+	if len(goroutines) == 0 {
+		return nil, err
+	}
+	c := &Context{
+		Goroutines:   goroutines,
+		localgoroot:  runtime.GOROOT(),
+		localgopaths: getGOPATHs(),
+	}
+	nameArguments(goroutines)
+	// Corresponding local values on the host for Context.
+	if guesspaths {
+		c.findRoots()
+		for _, r := range c.Goroutines {
+			// Note that this is important to call it even if
+			// c.GOROOT == c.localgoroot.
+			r.updateLocations(c.GOROOT, c.localgoroot, c.GOPATHs)
+		}
+	}
+	return c, err
+}
+
+// Private stuff.
+
+const (
+	lockedToThread   = "locked to thread"
+	elided           = "...additional frames elided..."
+	raceHeaderFooter = "=================="
+	raceHeader       = "WARNING: DATA RACE"
+)
+
+// These are effectively constants.
+var (
+	// TODO(maruel): Handle corrupted stack cases:
+	// - missed stack barrier
+	// - found next stack barrier at 0x123; expected
+	// - runtime: unexpected return pc for FUNC_NAME called from 0x123
+
+	reRoutineHeader = regexp.MustCompile("^([ \t]*)goroutine (\\d+) \\[([^\\]]+)\\]\\:$")
+	reMinutes       = regexp.MustCompile("^(\\d+) minutes$")
+	reUnavail       = regexp.MustCompile("^(?:\t| +)goroutine running on other thread; stack unavailable")
+	// See gentraceback() in src/runtime/traceback.go for more information.
+	// - Sometimes the source file comes up as "<autogenerated>". It is the
+	//   compiler than generated these, not the runtime.
+	// - The tab may be replaced with spaces when a user copy-paste it, handle
+	//   this transparently.
+	// - "runtime.gopanic" is explicitly replaced with "panic" by gentraceback().
+	// - The +0x123 byte offset is printed when frame.pc > _func.entry. _func is
+	//   generated by the linker.
+	// - The +0x123 byte offset is not included with generated code, e.g. unnamed
+	//   functions "func·006()" which is generally go func() { ... }()
+	//   statements. Since the _func is generated at runtime, it's probably why
+	//   _func.entry is not set.
+	// - C calls may have fp=0x123 sp=0x123 appended. I think it normally happens
+	//   when a signal is not correctly handled. It is printed with m.throwing>0.
+	//   These are discarded.
+	// - For cgo, the source file may be "??".
+	reFile = regexp.MustCompile("^(?:\t| +)(\\?\\?|\\<autogenerated\\>|.+\\.(?:c|go|s))\\:(\\d+)(?:| \\+0x[0-9a-f]+)(?:| fp=0x[0-9a-f]+ sp=0x[0-9a-f]+(?:| pc=0x[0-9a-f]+))$")
+	// Sadly, it doesn't note the goroutine number so we could cascade them per
+	// parenthood.
+	reCreated = regexp.MustCompile("^created by (.+)$")
+	reFunc    = regexp.MustCompile("^(.+)\\((.*)\\)$")
+
+	// See https://github.com/llvm/llvm-project/blob/master/compiler-rt/lib/tsan/rtl/tsan_report.cc
+	// for the code generating these messages. Please note only the block in
+	//   #else  // #if !SANITIZER_GO
+	// is used.
+	// TODO(maruel): "    [failed to restore the stack]\n\n"
+	// TODO(maruel): "Global var %s of size %zu at %p declared at %s:%zu\n"
+	reRaceOperationHeader             = regexp.MustCompile("^(Read|Write) at (0x[0-9a-f]+) by goroutine (\\d+):$")
+	reRacePreviousOperationHeader     = regexp.MustCompile("^Previous (read|write) at (0x[0-9a-f]+) by goroutine (\\d+):$")
+	reRacePreviousOperationMainHeader = regexp.MustCompile("^Previous (read|write) at (0x[0-9a-f]+) by main goroutine:$")
+	reRaceGoroutine                   = regexp.MustCompile("^Goroutine (\\d+) \\((running|finished)\\) created at:$")
+)
+
+func parseDump(r io.Reader, out io.Writer) ([]*Goroutine, error) {
+	scanner := bufio.NewScanner(r)
+	scanner.Split(scanLines)
+	// Do not enable race detection parsing yet, since it cannot be returned in
+	// Context at the moment.
+	s := scanningState{}
+	for scanner.Scan() {
+		line, err := s.scan(scanner.Text())
+		if line != "" {
+			_, _ = io.WriteString(out, line)
+		}
+		if err != nil {
+			return s.goroutines, err
+		}
+	}
+	return s.goroutines, scanner.Err()
+}
+
+// scanLines is similar to bufio.ScanLines except that it:
+//     - doesn't drop '\n'
+//     - doesn't strip '\r'
+//     - returns when the data is bufio.MaxScanTokenSize bytes
+func scanLines(data []byte, atEOF bool) (advance int, token []byte, err error) {
+	if atEOF && len(data) == 0 {
+		return 0, nil, nil
+	}
+	if i := bytes.IndexByte(data, '\n'); i >= 0 {
+		return i + 1, data[0 : i+1], nil
+	}
+	if atEOF {
+		return len(data), data, nil
+	}
+	if len(data) >= bufio.MaxScanTokenSize {
+		// Returns the line even if it is not at EOF nor has a '\n', otherwise the
+		// scanner will return bufio.ErrTooLong which is definitely not what we
+		// want.
+		return len(data), data, nil
+	}
+	return 0, nil, nil
+}
+
+// state is the state of the scan to detect and process a stack trace.
+type state int
+
+// Initial state is normal. Other states are when a stack trace is detected.
+const (
+	// Outside a stack trace.
+	// to: gotRoutineHeader, raceHeader1
+	normal state = iota
+
+	// Panic stack trace:
+
+	// Empty line between goroutines.
+	// from: gotFileCreated, gotFileFunc
+	// to: gotRoutineHeader, normal
+	betweenRoutine
+	// Goroutine header was found, e.g. "goroutine 1 [running]:"
+	// from: normal
+	// to: gotUnavail, gotFunc
+	gotRoutineHeader
+	// Function call line was found, e.g. "main.main()"
+	// from: gotRoutineHeader
+	// to: gotFile
+	gotFunc
+	// Goroutine creation line was found, e.g. "created by main.glob..func4"
+	// from: gotFileFunc
+	// to: gotFileCreated
+	gotCreated
+	// File header was found, e.g. "\t/foo/bar/baz.go:116 +0x35"
+	// from: gotFunc
+	// to: gotFunc, gotCreated, betweenRoutine, normal
+	gotFileFunc
+	// File header was found, e.g. "\t/foo/bar/baz.go:116 +0x35"
+	// from: gotCreated
+	// to: betweenRoutine, normal
+	gotFileCreated
+	// State when the goroutine stack is instead is reUnavail.
+	// from: gotRoutineHeader
+	// to: betweenRoutine, gotCreated
+	gotUnavail
+
+	// Race detector:
+
+	// Got "=================="
+	// from: normal
+	// to: normal, gotRaceHeader
+	gotRaceHeader1
+	// Got "WARNING: DATA RACE"
+	// from: gotRaceHeader1
+	// to: normal, gotRaceOperationHeader
+	gotRaceHeader
+	// A race operation was found, e.g. "Read at 0x00c0000e4030 by goroutine 7:"
+	// from: gotRaceHeader
+	// to: normal, gotRaceOperationFunc
+	gotRaceOperationHeader
+	// Function that caused the race, e.g. "  main.panicRace.func1()"
+	// from: gotRaceOperationHeader
+	// to: normal, gotRaceOperationFile
+	gotRaceOperationFunc
+	// Function that caused the race, e.g. "  main.panicRace.func1()"
+	// from: gotRaceOperationFunc
+	// to: normal, betweenRaces
+	gotRaceOperationFile
+	// Goroutine header, e.g. "Goroutine 7 (running) created at:"
+	// from: betweenRaces
+	// to: normal, gotRaceOperationHeader
+	gotRaceGoroutineHeader
+	// Function that caused the race, e.g. "  main.panicRace.func1()"
+	// from: gotRaceGoroutineHeader
+	// to: normal, gotRaceGoroutineFile
+	gotRaceGoroutineFunc
+	// Function that caused the race, e.g. "  main.panicRace.func1()"
+	// from: gotRaceGoroutineFunc
+	// to: normal, betweenRaces
+	gotRaceGoroutineFile
+	// Empty line between goroutines.
+	// from: gotRaceOperationFile
+	// to: normal, gotRaceOperationHeader
+	betweenRaces
+)
+
+type raceOp struct {
+	write bool
+	addr  uint64
+	id    int
+}
+
+// scanningState is the state of the scan to detect and process a stack trace
+// and stores the traces found.
+type scanningState struct {
+	// Determines if race detection is enabled. Currently false since scan()
+	// would swallow the race detector output, but the data is not part of
+	// Context yet.
+	raceDetectionEnabled bool
+
+	// goroutines contains all the goroutines found.
+	goroutines []*Goroutine
+
+	state  state
+	prefix string
+	races  []raceOp
+}
+
+// scan scans one line, updates goroutines and move to the next state.
+func (s *scanningState) scan(line string) (string, error) {
+	var cur *Goroutine
+	if len(s.goroutines) != 0 {
+		cur = s.goroutines[len(s.goroutines)-1]
+	}
+	trimmed := line
+	if strings.HasSuffix(line, "\r\n") {
+		trimmed = line[:len(line)-2]
+	} else if strings.HasSuffix(line, "\n") {
+		trimmed = line[:len(line)-1]
+	} else {
+		// There's two cases:
+		// - It's the end of the stream and it's not terminating with EOL character.
+		// - The line is longer than bufio.MaxScanTokenSize
+		if s.state == normal {
+			return line, nil
+		}
+		// Let it flow. It's possible the last line was trimmed and we still want to parse it.
+	}
+
+	if trimmed != "" && s.prefix != "" {
+		// This can only be the case if s.state != normal or the line is empty.
+		if !strings.HasPrefix(trimmed, s.prefix) {
+			prefix := s.prefix
+			s.state = normal
+			s.prefix = ""
+			return "", fmt.Errorf("inconsistent indentation: %q, expected %q", trimmed, prefix)
+		}
+		trimmed = trimmed[len(s.prefix):]
+	}
+
+	switch s.state {
+	case normal:
+		// We could look for '^panic:' but this is more risky, there can be a lot
+		// of junk between this and the stack dump.
+		fallthrough
+	case betweenRoutine:
+		// Look for a goroutine header.
+		if match := reRoutineHeader.FindStringSubmatch(trimmed); match != nil {
+			if id, err := strconv.Atoi(match[2]); err == nil {
+				// See runtime/traceback.go.
+				// "<state>, \d+ minutes, locked to thread"
+				items := strings.Split(match[3], ", ")
+				sleep := 0
+				locked := false
+				for i := 1; i < len(items); i++ {
+					if items[i] == lockedToThread {
+						locked = true
+						continue
+					}
+					// Look for duration, if any.
+					if match2 := reMinutes.FindStringSubmatch(items[i]); match2 != nil {
+						sleep, _ = strconv.Atoi(match2[1])
+					}
+				}
+				g := &Goroutine{
+					Signature: Signature{
+						State:    items[0],
+						SleepMin: sleep,
+						SleepMax: sleep,
+						Locked:   locked,
+					},
+					ID:    id,
+					First: len(s.goroutines) == 0,
+				}
+				s.goroutines = append(s.goroutines, g)
+				s.state = gotRoutineHeader
+				s.prefix = match[1]
+				return "", nil
+			}
+		}
+		// Switch to race detection mode.
+		if s.raceDetectionEnabled && trimmed == raceHeaderFooter {
+			s.state = gotRaceHeader1
+			// Send the line to the user.
+			return line, nil
+		}
+		// Fallthrough.
+		s.state = normal
+		s.prefix = ""
+		return line, nil
+
+	case gotRoutineHeader:
+		if reUnavail.MatchString(trimmed) {
+			// Generate a fake stack entry.
+			cur.Stack.Calls = []Call{{SrcPath: "<unavailable>"}}
+			// Next line is expected to be an empty line.
+			s.state = gotUnavail
+			return "", nil
+		}
+		call, err := parseFunc(trimmed)
+		if call != nil {
+			cur.Stack.Calls = append(cur.Stack.Calls, *call)
+			s.state = gotFunc
+			return "", err
+		}
+		return "", fmt.Errorf("expected a function after a goroutine header, got: %q", strings.TrimSpace(trimmed))
+
+	case gotFunc:
+		// Look for a file.
+		if match := reFile.FindStringSubmatch(trimmed); match != nil {
+			num, err := strconv.Atoi(match[2])
+			if err != nil {
+				return "", fmt.Errorf("failed to parse int on line: %q", strings.TrimSpace(trimmed))
+			}
+			// cur.Stack.Calls is guaranteed to have at least one item.
+			i := len(cur.Stack.Calls) - 1
+			cur.Stack.Calls[i].SrcPath = match[1]
+			cur.Stack.Calls[i].Line = num
+			s.state = gotFileFunc
+			return "", nil
+		}
+		return "", fmt.Errorf("expected a file after a function, got: %q", strings.TrimSpace(trimmed))
+
+	case gotCreated:
+		// Look for a file.
+		if match := reFile.FindStringSubmatch(trimmed); match != nil {
+			num, err := strconv.Atoi(match[2])
+			if err != nil {
+				return "", fmt.Errorf("failed to parse int on line: %q", strings.TrimSpace(trimmed))
+			}
+			cur.CreatedBy.SrcPath = match[1]
+			cur.CreatedBy.Line = num
+			s.state = gotFileCreated
+			return "", nil
+		}
+		return "", fmt.Errorf("expected a file after a created line, got: %q", trimmed)
+
+	case gotFileFunc:
+		if match := reCreated.FindStringSubmatch(trimmed); match != nil {
+			cur.CreatedBy.Func.Raw = match[1]
+			s.state = gotCreated
+			return "", nil
+		}
+		if elided == trimmed {
+			cur.Stack.Elided = true
+			// TODO(maruel): New state.
+			return "", nil
+		}
+		call, err := parseFunc(trimmed)
+		if call != nil {
+			cur.Stack.Calls = append(cur.Stack.Calls, *call)
+			s.state = gotFunc
+			return "", err
+		}
+		if trimmed == "" {
+			s.state = betweenRoutine
+			return "", nil
+		}
+		// Back to normal state.
+		s.state = normal
+		s.prefix = ""
+		return line, nil
+
+	case gotFileCreated:
+		if trimmed == "" {
+			s.state = betweenRoutine
+			return "", nil
+		}
+		s.state = normal
+		s.prefix = ""
+		return line, nil
+
+	case gotUnavail:
+		if trimmed == "" {
+			s.state = betweenRoutine
+			return "", nil
+		}
+		if match := reCreated.FindStringSubmatch(trimmed); match != nil {
+			cur.CreatedBy.Func.Raw = match[1]
+			s.state = gotCreated
+			return "", nil
+		}
+		return "", fmt.Errorf("expected empty line after unavailable stack, got: %q", strings.TrimSpace(trimmed))
+
+	case gotRaceHeader1:
+		if raceHeader == trimmed {
+			s.state = gotRaceHeader
+			// Send the line to the user.
+			return line, nil
+		}
+		s.state = normal
+		return line, nil
+
+	case gotRaceHeader:
+		if match := reRaceOperationHeader.FindStringSubmatch(trimmed); match != nil {
+			w := match[1] == "Write"
+			addr, err := strconv.ParseUint(match[2], 0, 64)
+			if err != nil {
+				return "", fmt.Errorf("failed to parse address on line: %q", strings.TrimSpace(trimmed))
+			}
+			id, err := strconv.Atoi(match[3])
+			if err != nil {
+				return "", fmt.Errorf("failed to parse goroutine id on line: %q", strings.TrimSpace(trimmed))
+			}
+			s.races = append(s.races, raceOp{w, addr, id})
+			s.state = gotRaceOperationHeader
+			return "", nil
+		}
+		s.state = normal
+		return line, nil
+
+	case gotRaceOperationHeader:
+		call, err := parseFunc(trimmed)
+		if call != nil {
+			// TODO(maruel): Figure out.
+			//cur.Stack.Calls = append(cur.Stack.Calls, *call)
+			s.state = gotRaceOperationFunc
+			return "", err
+		}
+		return "", fmt.Errorf("expected a function after a race operation, got: %q", trimmed)
+
+	case gotRaceGoroutineHeader:
+		call, err := parseFunc(strings.TrimLeft(trimmed, "\t "))
+		if call != nil {
+			cur.Stack.Calls = append(cur.Stack.Calls, *call)
+			s.state = gotRaceGoroutineFunc
+			return "", err
+		}
+		return "", fmt.Errorf("expected a function after a race operation, got: %q", trimmed)
+
+	case gotRaceOperationFunc:
+		if match := reFile.FindStringSubmatch(trimmed); match != nil {
+			_, err := strconv.Atoi(match[2])
+			if err != nil {
+				return "", fmt.Errorf("failed to parse int on line: %q", strings.TrimSpace(trimmed))
+			}
+			/* TODO(maruel): Figure out.
+			// cur.Stack.Calls is guaranteed to have at least one item.
+			i := len(cur.Stack.Calls) - 1
+			cur.Stack.Calls[i].SrcPath = match[1]
+			cur.Stack.Calls[i].Line = num
+			*/
+			s.state = gotRaceOperationFile
+			return "", nil
+		}
+		return "", fmt.Errorf("expected a file after a race function, got: %q", trimmed)
+
+	case gotRaceGoroutineFunc:
+		if match := reFile.FindStringSubmatch(trimmed); match != nil {
+			num, err := strconv.Atoi(match[2])
+			if err != nil {
+				return "", fmt.Errorf("failed to parse int on line: %q", strings.TrimSpace(trimmed))
+			}
+			// cur.Stack.Calls is guaranteed to have at least one item.
+			i := len(cur.Stack.Calls) - 1
+			cur.Stack.Calls[i].SrcPath = match[1]
+			cur.Stack.Calls[i].Line = num
+			s.state = gotRaceGoroutineFile
+			return "", nil
+		}
+		return "", fmt.Errorf("expected a file after a race function, got: %q", trimmed)
+
+	case gotRaceOperationFile:
+		if trimmed == "" {
+			s.state = betweenRaces
+			return "", nil
+		}
+		return "", fmt.Errorf("expected an empty line after a race file, got: %q", trimmed)
+
+	case gotRaceGoroutineFile:
+		if trimmed == "" {
+			s.state = betweenRaces
+			return "", nil
+		}
+		if trimmed == raceHeaderFooter {
+			// Done.
+			s.state = normal
+			return "", nil
+		}
+		call, err := parseFunc(strings.TrimLeft(trimmed, "\t "))
+		if call != nil {
+			// TODO(maruel): Process match.
+			s.state = gotRaceGoroutineFunc
+			return "", err
+		}
+		return "", fmt.Errorf("expected a function or the end after a race file, got: %q", trimmed)
+
+	case betweenRaces:
+		// Either Previous or Goroutine.
+		if match := reRacePreviousOperationHeader.FindStringSubmatch(trimmed); match != nil {
+			w := match[1] == "write"
+			addr, err := strconv.ParseUint(match[2], 0, 64)
+			if err != nil {
+				return "", fmt.Errorf("failed to parse address on line: %q", strings.TrimSpace(trimmed))
+			}
+			id, err := strconv.Atoi(match[3])
+			if err != nil {
+				return "", fmt.Errorf("failed to parse goroutine id on line: %q", strings.TrimSpace(trimmed))
+			}
+			s.races = append(s.races, raceOp{w, addr, id})
+			s.state = gotRaceOperationHeader
+			return "", nil
+		}
+		if match := reRaceGoroutine.FindStringSubmatch(trimmed); match != nil {
+			id, err := strconv.Atoi(match[1])
+			if err != nil {
+				return "", fmt.Errorf("failed to parse goroutine id on line: %q", strings.TrimSpace(trimmed))
+			}
+			g := &Goroutine{
+				Signature: Signature{State: match[2]},
+				ID:        id,
+				First:     len(s.goroutines) == 0,
+			}
+			s.goroutines = append(s.goroutines, g)
+			s.state = gotRaceGoroutineHeader
+			return "", nil
+		}
+		return "", fmt.Errorf("expected an operator or goroutine, got: %q", trimmed)
+
+	default:
+		return "", errors.New("internal error")
+	}
+}
+
+// parseFunc only return an error if also returning a Call.
+func parseFunc(line string) (*Call, error) {
+	if match := reFunc.FindStringSubmatch(line); match != nil {
+		call := &Call{Func: Func{Raw: match[1]}}
+		for _, a := range strings.Split(match[2], ", ") {
+			if a == "..." {
+				call.Args.Elided = true
+				continue
+			}
+			if a == "" {
+				// Remaining values were dropped.
+				break
+			}
+			v, err := strconv.ParseUint(a, 0, 64)
+			if err != nil {
+				return call, fmt.Errorf("failed to parse int on line: %q", strings.TrimSpace(line))
+			}
+			call.Args.Values = append(call.Args.Values, Arg{Value: v})
+		}
+		return call, nil
+	}
+	return nil, nil
+}
+
+// hasPathPrefix returns true if any of s is the prefix of p.
+func hasPathPrefix(p string, s map[string]string) bool {
+	for prefix := range s {
+		if strings.HasPrefix(p, prefix+"/") {
+			return true
+		}
+	}
+	return false
+}
+
+// getFiles returns all the source files deduped and ordered.
+func getFiles(goroutines []*Goroutine) []string {
+	files := map[string]struct{}{}
+	for _, g := range goroutines {
+		for _, c := range g.Stack.Calls {
+			files[c.SrcPath] = struct{}{}
+		}
+	}
+	out := make([]string, 0, len(files))
+	for f := range files {
+		out = append(out, f)
+	}
+	sort.Strings(out)
+	return out
+}
+
+// splitPath splits a path into its components.
+//
+// The first item has its initial path separator kept.
+func splitPath(p string) []string {
+	if p == "" {
+		return nil
+	}
+	var out []string
+	s := ""
+	for _, c := range p {
+		if c != '/' || (len(out) == 0 && strings.Count(s, "/") == len(s)) {
+			s += string(c)
+		} else if s != "" {
+			out = append(out, s)
+			s = ""
+		}
+	}
+	if s != "" {
+		out = append(out, s)
+	}
+	return out
+}
+
+// isFile returns true if the path is a valid file.
+func isFile(p string) bool {
+	// TODO(maruel): Is it faster to open the file or to stat it? Worth a perf
+	// test on Windows.
+	i, err := os.Stat(p)
+	return err == nil && !i.IsDir()
+}
+
+// rootedIn returns a root if the file split in parts is rooted in root.
+func rootedIn(root string, parts []string) string {
+	//log.Printf("rootIn(%s, %v)", root, parts)
+	for i := 1; i < len(parts); i++ {
+		suffix := filepath.Join(parts[i:]...)
+		if isFile(filepath.Join(root, suffix)) {
+			return filepath.Join(parts[:i]...)
+		}
+	}
+	return ""
+}
+
+// findRoots sets member GOROOT and GOPATHs.
+func (c *Context) findRoots() {
+	c.GOPATHs = map[string]string{}
+	for _, f := range getFiles(c.Goroutines) {
+		// TODO(maruel): Could a stack dump have mixed cases? I think it's
+		// possible, need to confirm and handle.
+		//log.Printf("  Analyzing %s", f)
+		if c.GOROOT != "" && strings.HasPrefix(f, c.GOROOT+"/") {
+			continue
+		}
+		if hasPathPrefix(f, c.GOPATHs) {
+			continue
+		}
+		parts := splitPath(f)
+		if c.GOROOT == "" {
+			if r := rootedIn(c.localgoroot, parts); r != "" {
+				c.GOROOT = r
+				//log.Printf("Found GOROOT=%s", c.GOROOT)
+				continue
+			}
+		}
+		found := false
+		for _, l := range c.localgopaths {
+			if r := rootedIn(l, parts); r != "" {
+				//log.Printf("Found GOPATH=%s", r)
+				c.GOPATHs[r] = l
+				found = true
+				break
+			}
+		}
+		if !found {
+			// If the source is not found, just too bad.
+			//log.Printf("Failed to find locally: %s / %s", f, goroot)
+		}
+	}
+}
+
+func getGOPATHs() []string {
+	var out []string
+	for _, v := range filepath.SplitList(os.Getenv("GOPATH")) {
+		// Disallow non-absolute paths?
+		if v != "" {
+			out = append(out, v)
+		}
+	}
+	if len(out) == 0 {
+		homeDir := ""
+		u, err := user.Current()
+		if err != nil {
+			homeDir = os.Getenv("HOME")
+			if homeDir == "" {
+				panic(fmt.Sprintf("Could not get current user or $HOME: %s\n", err.Error()))
+			}
+		} else {
+			homeDir = u.HomeDir
+		}
+		out = []string{homeDir + "go"}
+	}
+	return out
+}