description: "What would change in the language spec?"
    validations:
      required: false

  - type: textarea
    id: informal-change
    attributes:
      label: "Informal Change"
      description: "Please also describe the change informally, as in a class teaching Go."
    validations:
      required: false

  - type: textarea
    id: go-backwards-compatiblity
    attributes:

	}
}

func TestUnreadRune(t *testing.T) {
	segments := []string{"Hello, world:", "日本語"}
	r := NewReader(&StringReader{data: segments})
	got := ""
	want := strings.Join(segments, "")
	// Normal execution.
	for {
		r1, _, err := r.ReadRune()
		if err != nil {
			if err != io.EOF {
				t.Error("unexpected error on ReadRune:", err)
			}
			break
		}
		got += string(r1)

// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

/*
Cgo enables the creation of Go packages that call C code.

# Using cgo with the go command

To use cgo write normal Go code that imports a pseudo-package "C".
The Go code can then refer to types such as C.size_t, variables such
as C.stdout, or functions such as C.putchar.

If the import of "C" is immediately preceded by a comment, that

</p>

<p>
The form <code>a … b</code> represents the set of characters from
<code>a</code> through <code>b</code> as alternatives. The horizontal
ellipsis <code>…</code> is also used elsewhere in the spec to informally denote various
enumerations or code snippets that are not further specified. The character <code>…</code>
(as opposed to the three characters <code>...</code>) is not a token of the Go
language.
</p>

for their own operations.
</p>

<h2 id="restrictions">Implementation Restrictions for Programs Containing Data Races</h2>

<p>
The preceding section gave a formal definition of data-race-free program execution.
This section informally describes the semantics that implementations must provide
for programs that do contain races.
</p>

<p>
Any implementation can, upon detecting a data race,

			}
			x = x<<8 | uint64(c)
		}
		if (x >> 63) > 0 {
			p.err = ErrHeader // Integer overflow
			return 0
		}
		if inv == 0xff {
			return ^int64(x)
		}
		return int64(x)
	}

	// Normal case is base-8 (octal) format.
	return p.parseOctal(b)
}

// formatNumeric encodes x into b using base-8 (octal) encoding if possible.
// Otherwise it will attempt to use base-256 (binary) encoding.

// deals with sparseDatas.
//
// However, the external API uses sparseHoles instead of sparseDatas because the
// zero value of sparseHoles logically represents a normal file (i.e., there are
// no holes in it). On the other hand, the zero value of sparseDatas implies
// that the file has no data in it, which is rather odd.
//

		{data2[:2048] + trash[:1], 1, io.ErrUnexpectedEOF},
		{data2[:2048] + trash[:511], 1, io.ErrUnexpectedEOF},
		{data2[:2048] + trash, 1, ErrHeader},
		{data2[:2560], 1, io.EOF}, // Exactly 2 empty blocks (normal end-of-stream)
		{data2[:2560] + trash[:1], 1, io.EOF},
		{data2[:2560] + trash[:511], 1, io.EOF},
		{data2[:2560] + trash, 1, io.EOF},
		{data2[:3072], 1, io.EOF},

pkg syscall (freebsd-arm64), const BPF_T_NONE = 3
pkg syscall (freebsd-arm64), const BPF_T_NONE ideal-int
pkg syscall (freebsd-arm64), const BPF_T_NORMAL = 0
pkg syscall (freebsd-arm64), const BPF_T_NORMAL ideal-int
pkg syscall (freebsd-arm64), const BPF_TAX = 0
pkg syscall (freebsd-arm64), const BPF_TAX ideal-int
pkg syscall (freebsd-arm64), const BPF_TXA = 128

pkg syscall (darwin-arm64), const MADV_FREE_REUSE = 8
pkg syscall (darwin-arm64), const MADV_FREE_REUSE ideal-int
pkg syscall (darwin-arm64), const MADV_NORMAL = 0
pkg syscall (darwin-arm64), const MADV_NORMAL ideal-int
pkg syscall (darwin-arm64), const MADV_RANDOM = 1
pkg syscall (darwin-arm64), const MADV_RANDOM ideal-int
pkg syscall (darwin-arm64), const MADV_SEQUENTIAL = 2