n = int64(m)
	if m != len(b) && err == nil {
		err = io.ErrShortWrite
	}
	return
}

// Reset resets the [Reader.Reader] to be reading from b.
func (r *Reader) Reset(b []byte) { *r = Reader{b, 0, -1} }

// NewReader returns a new [Reader.Reader] reading from b.

			r.ReadAt(buf[:], int64(i))
		}(i)
	}
	wg.Wait()
}

func TestEmptyReaderConcurrent(t *testing.T) {
	// Test for the race detector, to verify a Read that doesn't yield any bytes
	// is okay to use from multiple goroutines. This was our historic behavior.
	// See golang.org/issue/7856
	r := NewReader([]byte{})
	var wg sync.WaitGroup
	for i := 0; i < 5; i++ {
		wg.Add(2)
		go func() {
			defer wg.Done()

	Debug      = flag.Bool("debug", false, "dump instructions as they are parsed")
	OutputFile = flag.String("o", "", "output file; default foo.o for /a/b/c/foo.s as first argument")
	TrimPath   = flag.String("trimpath", "", "remove prefix from recorded source file paths")
	Shared     = flag.Bool("shared", false, "generate code that can be linked into a shared library")

		}
	}
	if crawled[url] {
		return
	}
	crawled[url] = true

	wg.Add(1)
	go func() {
		urlq <- url
	}()
}

func addProblem(url, errmsg string) {
	msg := fmt.Sprintf("Error on %s: %s (from %s)", url, errmsg, linkSources[url])
	if *verbose {
		log.Print(msg)
	}
	problems = append(problems, msg)
}

func crawlLoop() {
	for url := range urlq {
		if err := doCrawl(url); err != nil {

// Arenas are useful for improving efficiency as they may be freed back to
// the runtime manually, though any memory obtained from freed arenas must
// not be accessed once that happens. An Arena is automatically freed once
// it is no longer referenced, so it must be kept alive (see runtime.KeepAlive)
// until any memory allocated from it is no longer needed.
//
// An Arena must never be used concurrently by multiple goroutines.
type Arena struct {

		}
		// There is one final token to be delivered, which may be the empty string.
		// Returning bufio.ErrFinalToken here tells Scan there are no more tokens after this
		// but does not trigger an error to be returned from Scan itself.
		return 0, data, bufio.ErrFinalToken
	}
	scanner.Split(onComma)
	// Scan.
	for scanner.Scan() {
		fmt.Printf("%q ", scanner.Text())
	}
	if err := scanner.Err(); err != nil {

// (due to the printer possibly inserting newlines because of position
// information) operators.
var gofmtLineReplacer = strings.NewReplacer(
	// Want to replace \n without ; after everything from
	// https://golang.org/ref/spec#Operators_and_punctuation
	// EXCEPT ++ -- ) ] }
	"++\n", "++;",
	"--\n", "--;",

	"+\n", "+ ",
	"-\n", "- ",
	"*\n", "* ",
	"/\n", "/ ",
	"%\n", "% ",

	c.SetCallback(cb)
	s := c.Call()
	if s != "Callback::run" {
		fatal("unexpected string from Call: %q", s)
	}
	c.DelCallback()
}

func testCallback() {
	c := NewCaller()
	cb := NewDirectorCallback(&GoCallback{})
	c.SetCallback(cb)
	s := c.Call()
	if s != "GoCallback.Run" {
		fatal("unexpected string from Call with callback: %q", s)
	}
	c.DelCallback()
	DeleteDirectorCallback(cb)

		case "linux":
			// Copied from golang.org/x/sys/unix/dev_linux.go.
			major := uint32((dev & 0x00000000000fff00) >> 8)
			major |= uint32((dev & 0xfffff00000000000) >> 32)
			minor := uint32((dev & 0x00000000000000ff) >> 0)
			minor |= uint32((dev & 0x00000ffffff00000) >> 12)
			h.Devmajor, h.Devminor = int64(major), int64(minor)
		case "darwin", "ios":
			// Copied from golang.org/x/sys/unix/dev_darwin.go.

		nproc = 7
	}
	if setNproc {
		var rlim syscall.Rlimit
		if syscall.Getrlimit(nproc, &rlim) == nil {
			max := int(rlim.Cur) / (threads + 5)
			if attempts > max {
				t.Logf("lowering attempts from %d to %d for RLIMIT_NPROC", attempts, max)
				attempts = max
			}
		}
	}

	if os.Getenv("test18146") == "exec" {
		runtime.GOMAXPROCS(1)
		for n := threads; n > 0; n-- {
			go func() {
				for {