if err := b.UnreadByte(); err == nil {
		t.Fatal("UnreadByte after ReadByte at EOF: got no error")
	}

	// check not at EOF
	b.WriteString("abcdefghijklmnopqrstuvwxyz")

	// after unsuccessful read
	if n, err := b.Read(nil); n != 0 || err != nil {
		t.Fatalf("Read(nil) = %d,%v; want 0,nil", n, err)
	}
	if err := b.UnreadByte(); err == nil {
		t.Fatal("UnreadByte after Read(nil): got no error")
	}

		// say "pkg syscall (darwin-amd64), type RawSockaddrInet6 struct" is missing.
		// See https://go.dev/issue/4303.
		{
			name: "contexts reconverging after api/next/* update",
			features: []string{
				"A",
				"pkg syscall, type RawSockaddrInet6 struct",
			},
			required: []string{
				"A",

	{"[X0]", "register list: expected '-' after `[X0`, found ']'"},
	{"[X0-]", "register list: bad high register in `[X0-]`"},
	{"[X0-x]", "register list: bad high register in `[X0-x`"},
	{"[X0-X1-X2]", "register list: expected ']' after `[X0-X1`, found '-'"},
	{"[X0,X3]", "register list: expected '-' after `[X0`, found ','"},
	{"[X0,X1,X2,X3]", "register list: expected '-' after `[X0`, found ','"},

</pre>

<p>
the variable <code>a</code> will be initialized after <code>b</code> but
whether <code>x</code> is initialized before <code>b</code>, between
<code>b</code> and <code>a</code>, or after <code>a</code>, and
thus also the moment at which <code>sideEffect()</code> is called (before
or after <code>x</code> is initialized) is not specified.
</p>

<p>

	extern GoInt64 MyFunction(int arg1, int arg2, GoString arg3);
	extern struct MyFunction2_return MyFunction2(int arg1, int arg2, GoString arg3);

found in the _cgo_export.h generated header, after any preambles
copied from the cgo input files. Functions with multiple
return values are mapped to functions returning a struct.

Not all Go types can be mapped to C types in a useful way.

			{
				Name:     "bar.txt",
				Content:  []byte("bar\n"),
				Modified: time.Date(2012, 3, 8, 16, 59, 12, 0, timeZone(-8*time.Hour)),
				Mode:     0644,
			},
		},
	},
	{
		// created by Go, after we wrote the "optional" data
		// descriptor signatures (which are required by macOS)
		Name: "go-with-datadesc-sig.zip",
		File: []ZipTestFile{
			{
				Name:     "foo.txt",
				Content:  []byte("foo\n"),

# license that can be found in the LICENSE file.

set -e
if [ ! -f make.bash ]; then
	echo 'all.bash must be run from $GOROOT/src' 1>&2
	exit 1
fi
. ./make.bash "$@" --no-banner
bash run.bash --no-rebuild

	mu sync.Mutex // guards Close and Write
	fw *flate.Writer
}

func (w *pooledFlateWriter) Write(p []byte) (n int, err error) {
	w.mu.Lock()
	defer w.mu.Unlock()
	if w.fw == nil {
		return 0, errors.New("Write after Close")
	}
	return w.fw.Write(p)
}

func (w *pooledFlateWriter) Close() error {
	w.mu.Lock()
	defer w.mu.Unlock()
	var err error
	if w.fw != nil {
		err = w.fw.Close()
		flateWriterPool.Put(w.fw)

      description: Breaking the Go 1 compatibility guarantee is a large cost and requires a large benefit.
      placeholder: |
       Yes or No

       If yes, 
        1. Show example code before and after the change.

    validations:
      required: true

  - type: textarea
    id: orthogonality
    attributes:
      label: "Orthogonality: How does this change interact or overlap with existing features?"

// license that can be found in the LICENSE file.

// Package tar implements access to tar archives.
//
// Tape archives (tar) are a file format for storing a sequence of files that
// can be read and written in a streaming manner.
// This package aims to cover most variations of the format,
// including those produced by GNU and BSD tar tools.
package tar

import (
	"errors"
	"fmt"
	"internal/godebug"
	"io/fs"
	"math"
	"path"