Adding upstream version 1.16.10.upstream/1.16.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1020 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/ssa/debug_test.go b/src/cmd/compile/internal/ssa/debug_test.go
new file mode 100644
index 0000000..3346312
--- /dev/null
+++ b/src/cmd/compile/internal/ssa/debug_test.go
@@ -0,0 +1,1020 @@
+// Copyright 2017 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 ssa_test
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"internal/testenv"
+	"io"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+)
+
+var (
+	update  = flag.Bool("u", false, "update test reference files")
+	verbose = flag.Bool("v", false, "print debugger interactions (very verbose)")
+	dryrun  = flag.Bool("n", false, "just print the command line and first debugging bits")
+	useGdb  = flag.Bool("g", false, "use Gdb instead of Delve (dlv), use gdb reference files")
+	force   = flag.Bool("f", false, "force run under not linux-amd64; also do not use tempdir")
+	repeats = flag.Bool("r", false, "detect repeats in debug steps and don't ignore them")
+	inlines = flag.Bool("i", false, "do inlining for gdb (makes testing flaky till inlining info is correct)")
+)
+
+var (
+	hexRe                 = regexp.MustCompile("0x[a-zA-Z0-9]+")
+	numRe                 = regexp.MustCompile("-?[0-9]+")
+	stringRe              = regexp.MustCompile("\"([^\\\"]|(\\.))*\"")
+	leadingDollarNumberRe = regexp.MustCompile("^[$][0-9]+")
+	optOutGdbRe           = regexp.MustCompile("[<]optimized out[>]")
+	numberColonRe         = regexp.MustCompile("^ *[0-9]+:")
+)
+
+var gdb = "gdb"      // Might be "ggdb" on Darwin, because gdb no longer part of XCode
+var debugger = "dlv" // For naming files, etc.
+
+var gogcflags = os.Getenv("GO_GCFLAGS")
+
+// optimizedLibs usually means "not running in a noopt test builder".
+var optimizedLibs = (!strings.Contains(gogcflags, "-N") && !strings.Contains(gogcflags, "-l"))
+
+// TestNexting go-builds a file, then uses a debugger (default delve, optionally gdb)
+// to next through the generated executable, recording each line landed at, and
+// then compares those lines with reference file(s).
+// Flag -u updates the reference file(s).
+// Flag -g changes the debugger to gdb (and uses gdb-specific reference files)
+// Flag -v is ever-so-slightly verbose.
+// Flag -n is for dry-run, and prints the shell and first debug commands.
+//
+// Because this test (combined with existing compiler deficiencies) is flaky,
+// for gdb-based testing by default inlining is disabled
+// (otherwise output depends on library internals)
+// and for both gdb and dlv by default repeated lines in the next stream are ignored
+// (because this appears to be timing-dependent in gdb, and the cleanest fix is in code common to gdb and dlv).
+//
+// Also by default, any source code outside of .../testdata/ is not mentioned
+// in the debugging histories.  This deals both with inlined library code once
+// the compiler is generating clean inline records, and also deals with
+// runtime code between return from main and process exit.  This is hidden
+// so that those files (in the runtime/library) can change without affecting
+// this test.
+//
+// These choices can be reversed with -i (inlining on) and -r (repeats detected) which
+// will also cause their own failures against the expected outputs.  Note that if the compiler
+// and debugger were behaving properly, the inlined code and repeated lines would not appear,
+// so the expected output is closer to what we hope to see, though it also encodes all our
+// current bugs.
+//
+// The file being tested may contain comments of the form
+// //DBG-TAG=(v1,v2,v3)
+// where DBG = {gdb,dlv} and TAG={dbg,opt}
+// each variable may optionally be followed by a / and one or more of S,A,N,O
+// to indicate normalization of Strings, (hex) addresses, and numbers.
+// "O" is an explicit indication that we expect it to be optimized out.
+// For example:
+//
+// 	if len(os.Args) > 1 { //gdb-dbg=(hist/A,cannedInput/A) //dlv-dbg=(hist/A,cannedInput/A)
+//
+// TODO: not implemented for Delve yet, but this is the plan
+//
+// After a compiler change that causes a difference in the debug behavior, check
+// to see if it is sensible or not, and if it is, update the reference files with
+// go test debug_test.go -args -u
+// (for Delve)
+// go test debug_test.go -args -u -d
+//
+func TestNexting(t *testing.T) {
+	testenv.SkipFlaky(t, 37404)
+
+	skipReasons := "" // Many possible skip reasons, list all that apply
+	if testing.Short() {
+		skipReasons = "not run in short mode; "
+	}
+	testenv.MustHaveGoBuild(t)
+
+	if *useGdb && !*force && !(runtime.GOOS == "linux" && runtime.GOARCH == "amd64") {
+		// Running gdb on OSX/darwin is very flaky.
+		// Sometimes it is called ggdb, depending on how it is installed.
+		// It also sometimes requires an admin password typed into a dialog box.
+		// Various architectures tend to differ slightly sometimes, and keeping them
+		// all in sync is a pain for people who don't have them all at hand,
+		// so limit testing to amd64 (for now)
+		skipReasons += "not run when testing gdb (-g) unless forced (-f) or linux-amd64; "
+	}
+
+	if !*useGdb && !*force && testenv.Builder() == "linux-386-longtest" {
+		// The latest version of Delve does support linux/386. However, the version currently
+		// installed in the linux-386-longtest builder does not. See golang.org/issue/39309.
+		skipReasons += "not run when testing delve on linux-386-longtest builder unless forced (-f); "
+	}
+
+	if *useGdb {
+		debugger = "gdb"
+		_, err := exec.LookPath(gdb)
+		if err != nil {
+			if runtime.GOOS != "darwin" {
+				skipReasons += "not run because gdb not on path; "
+			} else {
+				// On Darwin, MacPorts installs gdb as "ggdb".
+				_, err = exec.LookPath("ggdb")
+				if err != nil {
+					skipReasons += "not run because gdb (and also ggdb) request by -g option not on path; "
+				} else {
+					gdb = "ggdb"
+				}
+			}
+		}
+	} else { // Delve
+		debugger = "dlv"
+		_, err := exec.LookPath("dlv")
+		if err != nil {
+			skipReasons += "not run because dlv not on path; "
+		}
+	}
+
+	if skipReasons != "" {
+		t.Skip(skipReasons[:len(skipReasons)-2])
+	}
+
+	optFlags := "" // Whatever flags are needed to test debugging of optimized code.
+	dbgFlags := "-N -l"
+	if *useGdb && !*inlines {
+		// For gdb (default), disable inlining so that a compiler test does not depend on library code.
+		// TODO: Technically not necessary in 1.10 and later, but it causes a largish regression that needs investigation.
+		optFlags += " -l"
+	}
+
+	moreargs := []string{}
+	if *useGdb && (runtime.GOOS == "darwin" || runtime.GOOS == "windows") {
+		// gdb and lldb on Darwin do not deal with compressed dwarf.
+		// also, Windows.
+		moreargs = append(moreargs, "-ldflags=-compressdwarf=false")
+	}
+
+	subTest(t, debugger+"-dbg", "hist", dbgFlags, moreargs...)
+	subTest(t, debugger+"-dbg", "scopes", dbgFlags, moreargs...)
+	subTest(t, debugger+"-dbg", "i22558", dbgFlags, moreargs...)
+
+	subTest(t, debugger+"-dbg-race", "i22600", dbgFlags, append(moreargs, "-race")...)
+
+	optSubTest(t, debugger+"-opt", "hist", optFlags, 1000, moreargs...)
+	optSubTest(t, debugger+"-opt", "scopes", optFlags, 1000, moreargs...)
+
+	// Was optSubtest, this test is observed flaky on Linux in Docker on (busy) macOS, probably because of timing
+	// glitches in this harness.
+	// TODO get rid of timing glitches in this harness.
+	skipSubTest(t, debugger+"-opt", "infloop", optFlags, 10, moreargs...)
+
+}
+
+// subTest creates a subtest that compiles basename.go with the specified gcflags and additional compiler arguments,
+// then runs the debugger on the resulting binary, with any comment-specified actions matching tag triggered.
+func subTest(t *testing.T, tag string, basename string, gcflags string, moreargs ...string) {
+	t.Run(tag+"-"+basename, func(t *testing.T) {
+		if t.Name() == "TestNexting/gdb-dbg-i22558" {
+			testenv.SkipFlaky(t, 31263)
+		}
+		testNexting(t, basename, tag, gcflags, 1000, moreargs...)
+	})
+}
+
+// skipSubTest is the same as subTest except that it skips the test if execution is not forced (-f)
+func skipSubTest(t *testing.T, tag string, basename string, gcflags string, count int, moreargs ...string) {
+	t.Run(tag+"-"+basename, func(t *testing.T) {
+		if *force {
+			testNexting(t, basename, tag, gcflags, count, moreargs...)
+		} else {
+			t.Skip("skipping flaky test becaused not forced (-f)")
+		}
+	})
+}
+
+// optSubTest is the same as subTest except that it skips the test if the runtime and libraries
+// were not compiled with optimization turned on.  (The skip may not be necessary with Go 1.10 and later)
+func optSubTest(t *testing.T, tag string, basename string, gcflags string, count int, moreargs ...string) {
+	// If optimized test is run with unoptimized libraries (compiled with -N -l), it is very likely to fail.
+	// This occurs in the noopt builders (for example).
+	t.Run(tag+"-"+basename, func(t *testing.T) {
+		if *force || optimizedLibs {
+			testNexting(t, basename, tag, gcflags, count, moreargs...)
+		} else {
+			t.Skip("skipping for unoptimized stdlib/runtime")
+		}
+	})
+}
+
+func testNexting(t *testing.T, base, tag, gcflags string, count int, moreArgs ...string) {
+	// (1) In testdata, build sample.go into test-sample.<tag>
+	// (2) Run debugger gathering a history
+	// (3) Read expected history from testdata/sample.<tag>.nexts
+	// optionally, write out testdata/sample.<tag>.nexts
+
+	testbase := filepath.Join("testdata", base) + "." + tag
+	tmpbase := filepath.Join("testdata", "test-"+base+"."+tag)
+
+	// Use a temporary directory unless -f is specified
+	if !*force {
+		tmpdir, err := ioutil.TempDir("", "debug_test")
+		if err != nil {
+			panic(fmt.Sprintf("Problem creating TempDir, error %v\n", err))
+		}
+		tmpbase = filepath.Join(tmpdir, "test-"+base+"."+tag)
+		if *verbose {
+			fmt.Printf("Tempdir is %s\n", tmpdir)
+		}
+		defer os.RemoveAll(tmpdir)
+	}
+	exe := tmpbase
+
+	runGoArgs := []string{"build", "-o", exe, "-gcflags=all=" + gcflags}
+	runGoArgs = append(runGoArgs, moreArgs...)
+	runGoArgs = append(runGoArgs, filepath.Join("testdata", base+".go"))
+
+	runGo(t, "", runGoArgs...)
+
+	nextlog := testbase + ".nexts"
+	tmplog := tmpbase + ".nexts"
+	var dbg dbgr
+	if *useGdb {
+		dbg = newGdb(tag, exe)
+	} else {
+		dbg = newDelve(tag, exe)
+	}
+	h1 := runDbgr(dbg, count)
+	if *dryrun {
+		fmt.Printf("# Tag for above is %s\n", dbg.tag())
+		return
+	}
+	if *update {
+		h1.write(nextlog)
+	} else {
+		h0 := &nextHist{}
+		h0.read(nextlog)
+		if !h0.equals(h1) {
+			// Be very noisy about exactly what's wrong to simplify debugging.
+			h1.write(tmplog)
+			cmd := exec.Command("diff", "-u", nextlog, tmplog)
+			line := asCommandLine("", cmd)
+			bytes, err := cmd.CombinedOutput()
+			if err != nil && len(bytes) == 0 {
+				t.Fatalf("step/next histories differ, diff command %s failed with error=%v", line, err)
+			}
+			t.Fatalf("step/next histories differ, diff=\n%s", string(bytes))
+		}
+	}
+}
+
+type dbgr interface {
+	start()
+	stepnext(s string) bool // step or next, possible with parameter, gets line etc.  returns true for success, false for unsure response
+	quit()
+	hist() *nextHist
+	tag() string
+}
+
+func runDbgr(dbg dbgr, maxNext int) *nextHist {
+	dbg.start()
+	if *dryrun {
+		return nil
+	}
+	for i := 0; i < maxNext; i++ {
+		if !dbg.stepnext("n") {
+			break
+		}
+	}
+	dbg.quit()
+	h := dbg.hist()
+	return h
+}
+
+func runGo(t *testing.T, dir string, args ...string) string {
+	var stdout, stderr bytes.Buffer
+	cmd := exec.Command(testenv.GoToolPath(t), args...)
+	cmd.Dir = dir
+	if *dryrun {
+		fmt.Printf("%s\n", asCommandLine("", cmd))
+		return ""
+	}
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	if err := cmd.Run(); err != nil {
+		t.Fatalf("error running cmd (%s): %v\nstdout:\n%sstderr:\n%s\n", asCommandLine("", cmd), err, stdout.String(), stderr.String())
+	}
+
+	if s := stderr.String(); s != "" {
+		t.Fatalf("Stderr = %s\nWant empty", s)
+	}
+
+	return stdout.String()
+}
+
+// tstring provides two strings, o (stdout) and e (stderr)
+type tstring struct {
+	o string
+	e string
+}
+
+func (t tstring) String() string {
+	return t.o + t.e
+}
+
+type pos struct {
+	line uint32
+	file uint8 // Artifact of plans to implement differencing instead of calling out to diff.
+}
+
+type nextHist struct {
+	f2i   map[string]uint8
+	fs    []string
+	ps    []pos
+	texts []string
+	vars  [][]string
+}
+
+func (h *nextHist) write(filename string) {
+	file, err := os.Create(filename)
+	if err != nil {
+		panic(fmt.Sprintf("Problem opening %s, error %v\n", filename, err))
+	}
+	defer file.Close()
+	var lastfile uint8
+	for i, x := range h.texts {
+		p := h.ps[i]
+		if lastfile != p.file {
+			fmt.Fprintf(file, "  %s\n", h.fs[p.file-1])
+			lastfile = p.file
+		}
+		fmt.Fprintf(file, "%d:%s\n", p.line, x)
+		// TODO, normalize between gdb and dlv into a common, comparable format.
+		for _, y := range h.vars[i] {
+			y = strings.TrimSpace(y)
+			fmt.Fprintf(file, "%s\n", y)
+		}
+	}
+	file.Close()
+}
+
+func (h *nextHist) read(filename string) {
+	h.f2i = make(map[string]uint8)
+	bytes, err := ioutil.ReadFile(filename)
+	if err != nil {
+		panic(fmt.Sprintf("Problem reading %s, error %v\n", filename, err))
+	}
+	var lastfile string
+	lines := strings.Split(string(bytes), "\n")
+	for i, l := range lines {
+		if len(l) > 0 && l[0] != '#' {
+			if l[0] == ' ' {
+				// file -- first two characters expected to be "  "
+				lastfile = strings.TrimSpace(l)
+			} else if numberColonRe.MatchString(l) {
+				// line number -- <number>:<line>
+				colonPos := strings.Index(l, ":")
+				if colonPos == -1 {
+					panic(fmt.Sprintf("Line %d (%s) in file %s expected to contain '<number>:' but does not.\n", i+1, l, filename))
+				}
+				h.add(lastfile, l[0:colonPos], l[colonPos+1:])
+			} else {
+				h.addVar(l)
+			}
+		}
+	}
+}
+
+// add appends file (name), line (number) and text (string) to the history,
+// provided that the file+line combo does not repeat the previous position,
+// and provided that the file is within the testdata directory.  The return
+// value indicates whether the append occurred.
+func (h *nextHist) add(file, line, text string) bool {
+	// Only record source code in testdata unless the inlines flag is set
+	if !*inlines && !strings.Contains(file, "/testdata/") {
+		return false
+	}
+	fi := h.f2i[file]
+	if fi == 0 {
+		h.fs = append(h.fs, file)
+		fi = uint8(len(h.fs))
+		h.f2i[file] = fi
+	}
+
+	line = strings.TrimSpace(line)
+	var li int
+	var err error
+	if line != "" {
+		li, err = strconv.Atoi(line)
+		if err != nil {
+			panic(fmt.Sprintf("Non-numeric line: %s, error %v\n", line, err))
+		}
+	}
+	l := len(h.ps)
+	p := pos{line: uint32(li), file: fi}
+
+	if l == 0 || *repeats || h.ps[l-1] != p {
+		h.ps = append(h.ps, p)
+		h.texts = append(h.texts, text)
+		h.vars = append(h.vars, []string{})
+		return true
+	}
+	return false
+}
+
+func (h *nextHist) addVar(text string) {
+	l := len(h.texts)
+	h.vars[l-1] = append(h.vars[l-1], text)
+}
+
+func invertMapSU8(hf2i map[string]uint8) map[uint8]string {
+	hi2f := make(map[uint8]string)
+	for hs, i := range hf2i {
+		hi2f[i] = hs
+	}
+	return hi2f
+}
+
+func (h *nextHist) equals(k *nextHist) bool {
+	if len(h.f2i) != len(k.f2i) {
+		return false
+	}
+	if len(h.ps) != len(k.ps) {
+		return false
+	}
+	hi2f := invertMapSU8(h.f2i)
+	ki2f := invertMapSU8(k.f2i)
+
+	for i, hs := range hi2f {
+		if hs != ki2f[i] {
+			return false
+		}
+	}
+
+	for i, x := range h.ps {
+		if k.ps[i] != x {
+			return false
+		}
+	}
+
+	for i, hv := range h.vars {
+		kv := k.vars[i]
+		if len(hv) != len(kv) {
+			return false
+		}
+		for j, hvt := range hv {
+			if hvt != kv[j] {
+				return false
+			}
+		}
+	}
+
+	return true
+}
+
+// canonFileName strips everything before "/src/" from a filename.
+// This makes file names portable across different machines,
+// home directories, and temporary directories.
+func canonFileName(f string) string {
+	i := strings.Index(f, "/src/")
+	if i != -1 {
+		f = f[i+1:]
+	}
+	return f
+}
+
+/* Delve */
+
+type delveState struct {
+	cmd  *exec.Cmd
+	tagg string
+	*ioState
+	atLineRe         *regexp.Regexp // "\n =>"
+	funcFileLinePCre *regexp.Regexp // "^> ([^ ]+) ([^:]+):([0-9]+) .*[(]PC: (0x[a-z0-9]+)"
+	line             string
+	file             string
+	function         string
+}
+
+func newDelve(tag, executable string, args ...string) dbgr {
+	cmd := exec.Command("dlv", "exec", executable)
+	cmd.Env = replaceEnv(cmd.Env, "TERM", "dumb")
+	if len(args) > 0 {
+		cmd.Args = append(cmd.Args, "--")
+		cmd.Args = append(cmd.Args, args...)
+	}
+	s := &delveState{tagg: tag, cmd: cmd}
+	// HAHA Delve has control characters embedded to change the color of the => and the line number
+	// that would be '(\\x1b\\[[0-9;]+m)?' OR TERM=dumb
+	s.atLineRe = regexp.MustCompile("\n=>[[:space:]]+[0-9]+:(.*)")
+	s.funcFileLinePCre = regexp.MustCompile("> ([^ ]+) ([^:]+):([0-9]+) .*[(]PC: (0x[a-z0-9]+)[)]\n")
+	s.ioState = newIoState(s.cmd)
+	return s
+}
+
+func (s *delveState) tag() string {
+	return s.tagg
+}
+
+func (s *delveState) stepnext(ss string) bool {
+	x := s.ioState.writeReadExpect(ss+"\n", "[(]dlv[)] ")
+	excerpts := s.atLineRe.FindStringSubmatch(x.o)
+	locations := s.funcFileLinePCre.FindStringSubmatch(x.o)
+	excerpt := ""
+	if len(excerpts) > 1 {
+		excerpt = excerpts[1]
+	}
+	if len(locations) > 0 {
+		fn := canonFileName(locations[2])
+		if *verbose {
+			if s.file != fn {
+				fmt.Printf("%s\n", locations[2]) // don't canonocalize verbose logging
+			}
+			fmt.Printf("  %s\n", locations[3])
+		}
+		s.line = locations[3]
+		s.file = fn
+		s.function = locations[1]
+		s.ioState.history.add(s.file, s.line, excerpt)
+		// TODO: here is where variable processing will be added.  See gdbState.stepnext as a guide.
+		// Adding this may require some amount of normalization so that logs are comparable.
+		return true
+	}
+	if *verbose {
+		fmt.Printf("DID NOT MATCH EXPECTED NEXT OUTPUT\nO='%s'\nE='%s'\n", x.o, x.e)
+	}
+	return false
+}
+
+func (s *delveState) start() {
+	if *dryrun {
+		fmt.Printf("%s\n", asCommandLine("", s.cmd))
+		fmt.Printf("b main.test\n")
+		fmt.Printf("c\n")
+		return
+	}
+	err := s.cmd.Start()
+	if err != nil {
+		line := asCommandLine("", s.cmd)
+		panic(fmt.Sprintf("There was an error [start] running '%s', %v\n", line, err))
+	}
+	s.ioState.readExpecting(-1, 5000, "Type 'help' for list of commands.")
+	s.ioState.writeReadExpect("b main.test\n", "[(]dlv[)] ")
+	s.stepnext("c")
+}
+
+func (s *delveState) quit() {
+	expect("", s.ioState.writeRead("q\n"))
+}
+
+/* Gdb */
+
+type gdbState struct {
+	cmd  *exec.Cmd
+	tagg string
+	args []string
+	*ioState
+	atLineRe         *regexp.Regexp
+	funcFileLinePCre *regexp.Regexp
+	line             string
+	file             string
+	function         string
+}
+
+func newGdb(tag, executable string, args ...string) dbgr {
+	// Turn off shell, necessary for Darwin apparently
+	cmd := exec.Command(gdb, "-nx",
+		"-iex", fmt.Sprintf("add-auto-load-safe-path %s/src/runtime", runtime.GOROOT()),
+		"-ex", "set startup-with-shell off", executable)
+	cmd.Env = replaceEnv(cmd.Env, "TERM", "dumb")
+	s := &gdbState{tagg: tag, cmd: cmd, args: args}
+	s.atLineRe = regexp.MustCompile("(^|\n)([0-9]+)(.*)")
+	s.funcFileLinePCre = regexp.MustCompile(
+		"([^ ]+) [(][^)]*[)][ \\t\\n]+at ([^:]+):([0-9]+)")
+	// runtime.main () at /Users/drchase/GoogleDrive/work/go/src/runtime/proc.go:201
+	//                                    function              file    line
+	// Thread 2 hit Breakpoint 1, main.main () at /Users/drchase/GoogleDrive/work/debug/hist.go:18
+	s.ioState = newIoState(s.cmd)
+	return s
+}
+
+func (s *gdbState) tag() string {
+	return s.tagg
+}
+
+func (s *gdbState) start() {
+	run := "run"
+	for _, a := range s.args {
+		run += " " + a // Can't quote args for gdb, it will pass them through including the quotes
+	}
+	if *dryrun {
+		fmt.Printf("%s\n", asCommandLine("", s.cmd))
+		fmt.Printf("tbreak main.test\n")
+		fmt.Printf("%s\n", run)
+		return
+	}
+	err := s.cmd.Start()
+	if err != nil {
+		line := asCommandLine("", s.cmd)
+		panic(fmt.Sprintf("There was an error [start] running '%s', %v\n", line, err))
+	}
+	s.ioState.readSimpleExpecting("[(]gdb[)] ")
+	x := s.ioState.writeReadExpect("b main.test\n", "[(]gdb[)] ")
+	expect("Breakpoint [0-9]+ at", x)
+	s.stepnext(run)
+}
+
+func (s *gdbState) stepnext(ss string) bool {
+	x := s.ioState.writeReadExpect(ss+"\n", "[(]gdb[)] ")
+	excerpts := s.atLineRe.FindStringSubmatch(x.o)
+	locations := s.funcFileLinePCre.FindStringSubmatch(x.o)
+	excerpt := ""
+	addedLine := false
+	if len(excerpts) == 0 && len(locations) == 0 {
+		if *verbose {
+			fmt.Printf("DID NOT MATCH %s", x.o)
+		}
+		return false
+	}
+	if len(excerpts) > 0 {
+		excerpt = excerpts[3]
+	}
+	if len(locations) > 0 {
+		fn := canonFileName(locations[2])
+		if *verbose {
+			if s.file != fn {
+				fmt.Printf("%s\n", locations[2])
+			}
+			fmt.Printf("  %s\n", locations[3])
+		}
+		s.line = locations[3]
+		s.file = fn
+		s.function = locations[1]
+		addedLine = s.ioState.history.add(s.file, s.line, excerpt)
+	}
+	if len(excerpts) > 0 {
+		if *verbose {
+			fmt.Printf("  %s\n", excerpts[2])
+		}
+		s.line = excerpts[2]
+		addedLine = s.ioState.history.add(s.file, s.line, excerpt)
+	}
+
+	if !addedLine {
+		// True if this was a repeat line
+		return true
+	}
+	// Look for //gdb-<tag>=(v1,v2,v3) and print v1, v2, v3
+	vars := varsToPrint(excerpt, "//"+s.tag()+"=(")
+	for _, v := range vars {
+		response := printVariableAndNormalize(v, func(v string) string {
+			return s.ioState.writeReadExpect("p "+v+"\n", "[(]gdb[)] ").String()
+		})
+		s.ioState.history.addVar(response)
+	}
+	return true
+}
+
+// printVariableAndNormalize extracts any slash-indicated normalizing requests from the variable
+// name, then uses printer to get the value of the variable from the debugger, and then
+// normalizes and returns the response.
+func printVariableAndNormalize(v string, printer func(v string) string) string {
+	slashIndex := strings.Index(v, "/")
+	substitutions := ""
+	if slashIndex != -1 {
+		substitutions = v[slashIndex:]
+		v = v[:slashIndex]
+	}
+	response := printer(v)
+	// expect something like "$1 = ..."
+	dollar := strings.Index(response, "$")
+	cr := strings.Index(response, "\n")
+
+	if dollar == -1 { // some not entirely expected response, whine and carry on.
+		if cr == -1 {
+			response = strings.TrimSpace(response) // discards trailing newline
+			response = strings.Replace(response, "\n", "<BR>", -1)
+			return "$ Malformed response " + response
+		}
+		response = strings.TrimSpace(response[:cr])
+		return "$ " + response
+	}
+	if cr == -1 {
+		cr = len(response)
+	}
+	// Convert the leading $<number> into the variable name to enhance readability
+	// and reduce scope of diffs if an earlier print-variable is added.
+	response = strings.TrimSpace(response[dollar:cr])
+	response = leadingDollarNumberRe.ReplaceAllString(response, v)
+
+	// Normalize value as requested.
+	if strings.Contains(substitutions, "A") {
+		response = hexRe.ReplaceAllString(response, "<A>")
+	}
+	if strings.Contains(substitutions, "N") {
+		response = numRe.ReplaceAllString(response, "<N>")
+	}
+	if strings.Contains(substitutions, "S") {
+		response = stringRe.ReplaceAllString(response, "<S>")
+	}
+	if strings.Contains(substitutions, "O") {
+		response = optOutGdbRe.ReplaceAllString(response, "<Optimized out, as expected>")
+	}
+	return response
+}
+
+// varsToPrint takes a source code line, and extracts the comma-separated variable names
+// found between lookfor and the next ")".
+// For example, if line includes "... //gdb-foo=(v1,v2,v3)" and
+// lookfor="//gdb-foo=(", then varsToPrint returns ["v1", "v2", "v3"]
+func varsToPrint(line, lookfor string) []string {
+	var vars []string
+	if strings.Contains(line, lookfor) {
+		x := line[strings.Index(line, lookfor)+len(lookfor):]
+		end := strings.Index(x, ")")
+		if end == -1 {
+			panic(fmt.Sprintf("Saw variable list begin %s in %s but no closing ')'", lookfor, line))
+		}
+		vars = strings.Split(x[:end], ",")
+		for i, y := range vars {
+			vars[i] = strings.TrimSpace(y)
+		}
+	}
+	return vars
+}
+
+func (s *gdbState) quit() {
+	response := s.ioState.writeRead("q\n")
+	if strings.Contains(response.o, "Quit anyway? (y or n)") {
+		defer func() {
+			if r := recover(); r != nil {
+				if s, ok := r.(string); !(ok && strings.Contains(s, "'Y\n'")) {
+					// Not the panic that was expected.
+					fmt.Printf("Expected a broken pipe panic, but saw the following panic instead")
+					panic(r)
+				}
+			}
+		}()
+		s.ioState.writeRead("Y\n")
+	}
+}
+
+type ioState struct {
+	stdout  io.ReadCloser
+	stderr  io.ReadCloser
+	stdin   io.WriteCloser
+	outChan chan string
+	errChan chan string
+	last    tstring // Output of previous step
+	history *nextHist
+}
+
+func newIoState(cmd *exec.Cmd) *ioState {
+	var err error
+	s := &ioState{}
+	s.history = &nextHist{}
+	s.history.f2i = make(map[string]uint8)
+	s.stdout, err = cmd.StdoutPipe()
+	line := asCommandLine("", cmd)
+	if err != nil {
+		panic(fmt.Sprintf("There was an error [stdoutpipe] running '%s', %v\n", line, err))
+	}
+	s.stderr, err = cmd.StderrPipe()
+	if err != nil {
+		panic(fmt.Sprintf("There was an error [stdouterr] running '%s', %v\n", line, err))
+	}
+	s.stdin, err = cmd.StdinPipe()
+	if err != nil {
+		panic(fmt.Sprintf("There was an error [stdinpipe] running '%s', %v\n", line, err))
+	}
+
+	s.outChan = make(chan string, 1)
+	s.errChan = make(chan string, 1)
+	go func() {
+		buffer := make([]byte, 4096)
+		for {
+			n, err := s.stdout.Read(buffer)
+			if n > 0 {
+				s.outChan <- string(buffer[0:n])
+			}
+			if err == io.EOF || n == 0 {
+				break
+			}
+			if err != nil {
+				fmt.Printf("Saw an error forwarding stdout")
+				break
+			}
+		}
+		close(s.outChan)
+		s.stdout.Close()
+	}()
+
+	go func() {
+		buffer := make([]byte, 4096)
+		for {
+			n, err := s.stderr.Read(buffer)
+			if n > 0 {
+				s.errChan <- string(buffer[0:n])
+			}
+			if err == io.EOF || n == 0 {
+				break
+			}
+			if err != nil {
+				fmt.Printf("Saw an error forwarding stderr")
+				break
+			}
+		}
+		close(s.errChan)
+		s.stderr.Close()
+	}()
+	return s
+}
+
+func (s *ioState) hist() *nextHist {
+	return s.history
+}
+
+// writeRead writes ss, then reads stdout and stderr, waiting 500ms to
+// be sure all the output has appeared.
+func (s *ioState) writeRead(ss string) tstring {
+	if *verbose {
+		fmt.Printf("=> %s", ss)
+	}
+	_, err := io.WriteString(s.stdin, ss)
+	if err != nil {
+		panic(fmt.Sprintf("There was an error writing '%s', %v\n", ss, err))
+	}
+	return s.readExpecting(-1, 500, "")
+}
+
+// writeReadExpect writes ss, then reads stdout and stderr until something
+// that matches expectRE appears.  expectRE should not be ""
+func (s *ioState) writeReadExpect(ss, expectRE string) tstring {
+	if *verbose {
+		fmt.Printf("=> %s", ss)
+	}
+	if expectRE == "" {
+		panic("expectRE should not be empty; use .* instead")
+	}
+	_, err := io.WriteString(s.stdin, ss)
+	if err != nil {
+		panic(fmt.Sprintf("There was an error writing '%s', %v\n", ss, err))
+	}
+	return s.readSimpleExpecting(expectRE)
+}
+
+func (s *ioState) readExpecting(millis, interlineTimeout int, expectedRE string) tstring {
+	timeout := time.Millisecond * time.Duration(millis)
+	interline := time.Millisecond * time.Duration(interlineTimeout)
+	s.last = tstring{}
+	var re *regexp.Regexp
+	if expectedRE != "" {
+		re = regexp.MustCompile(expectedRE)
+	}
+loop:
+	for {
+		var timer <-chan time.Time
+		if timeout > 0 {
+			timer = time.After(timeout)
+		}
+		select {
+		case x, ok := <-s.outChan:
+			if !ok {
+				s.outChan = nil
+			}
+			s.last.o += x
+		case x, ok := <-s.errChan:
+			if !ok {
+				s.errChan = nil
+			}
+			s.last.e += x
+		case <-timer:
+			break loop
+		}
+		if re != nil {
+			if re.MatchString(s.last.o) {
+				break
+			}
+			if re.MatchString(s.last.e) {
+				break
+			}
+		}
+		timeout = interline
+	}
+	if *verbose {
+		fmt.Printf("<= %s%s", s.last.o, s.last.e)
+	}
+	return s.last
+}
+
+func (s *ioState) readSimpleExpecting(expectedRE string) tstring {
+	s.last = tstring{}
+	var re *regexp.Regexp
+	if expectedRE != "" {
+		re = regexp.MustCompile(expectedRE)
+	}
+	for {
+		select {
+		case x, ok := <-s.outChan:
+			if !ok {
+				s.outChan = nil
+			}
+			s.last.o += x
+		case x, ok := <-s.errChan:
+			if !ok {
+				s.errChan = nil
+			}
+			s.last.e += x
+		}
+		if re != nil {
+			if re.MatchString(s.last.o) {
+				break
+			}
+			if re.MatchString(s.last.e) {
+				break
+			}
+		}
+	}
+	if *verbose {
+		fmt.Printf("<= %s%s", s.last.o, s.last.e)
+	}
+	return s.last
+}
+
+// replaceEnv returns a new environment derived from env
+// by removing any existing definition of ev and adding ev=evv.
+func replaceEnv(env []string, ev string, evv string) []string {
+	evplus := ev + "="
+	var found bool
+	for i, v := range env {
+		if strings.HasPrefix(v, evplus) {
+			found = true
+			env[i] = evplus + evv
+		}
+	}
+	if !found {
+		env = append(env, evplus+evv)
+	}
+	return env
+}
+
+// asCommandLine renders cmd as something that could be copy-and-pasted into a command line
+// If cwd is not empty and different from the command's directory, prepend an appropriate "cd"
+func asCommandLine(cwd string, cmd *exec.Cmd) string {
+	s := "("
+	if cmd.Dir != "" && cmd.Dir != cwd {
+		s += "cd" + escape(cmd.Dir) + ";"
+	}
+	for _, e := range cmd.Env {
+		if !strings.HasPrefix(e, "PATH=") &&
+			!strings.HasPrefix(e, "HOME=") &&
+			!strings.HasPrefix(e, "USER=") &&
+			!strings.HasPrefix(e, "SHELL=") {
+			s += escape(e)
+		}
+	}
+	for _, a := range cmd.Args {
+		s += escape(a)
+	}
+	s += " )"
+	return s
+}
+
+// escape inserts escapes appropriate for use in a shell command line
+func escape(s string) string {
+	s = strings.Replace(s, "\\", "\\\\", -1)
+	s = strings.Replace(s, "'", "\\'", -1)
+	// Conservative guess at characters that will force quoting
+	if strings.ContainsAny(s, "\\ ;#*&$~?!|[]()<>{}`") {
+		s = " '" + s + "'"
+	} else {
+		s = " " + s
+	}
+	return s
+}
+
+func expect(want string, got tstring) {
+	if want != "" {
+		match, err := regexp.MatchString(want, got.o)
+		if err != nil {
+			panic(fmt.Sprintf("Error for regexp %s, %v\n", want, err))
+		}
+		if match {
+			return
+		}
+		// Ignore error as we have already checked for it before
+		match, _ = regexp.MatchString(want, got.e)
+		if match {
+			return
+		}
+		fmt.Printf("EXPECTED '%s'\n GOT O='%s'\nAND E='%s'\n", want, got.o, got.e)
+	}
+}