[runtime/metrics](/pkg/runtime/metrics/) counter
named `/godebug/non-default-behavior/<name>:events`
that counts the number of times a particular program's
behavior has changed based on a non-default value
for that setting.
For example, when `GODEBUG=http2client=0` is set,
`/godebug/non-default-behavior/http2client:events`
counts the number of HTTP transports that the program
has configured without HTTP/2 support.

// the token is the last token.
//
// The value is useful to stop processing early or when it is necessary to
// deliver a final empty token (which is different from a nil token).
// One could achieve the same behavior with a custom error value but
// providing one here is tidier.
// See the emptyFinalToken example for a use of this value.
var ErrFinalToken = errors.New("final token")

"C? Go? Cgo!" for an introduction to using cgo:
https://golang.org/doc/articles/c_go_cgo.html.

CFLAGS, CPPFLAGS, CXXFLAGS, FFLAGS and LDFLAGS may be defined with pseudo
#cgo directives within these comments to tweak the behavior of the C, C++
or Fortran compiler. Values defined in multiple directives are concatenated
together. The directive can include a list of build constraints limiting its
effect to systems satisfying one of the constraints

				"ctime":                         "1386065770.449252304",
				"SCHILY.xattr.security.selinux": "unconfined_u:object_r:default_t:s0\x00",
			},
			Format: FormatPAX,
		}},
	}, {
		// Matches the behavior of GNU, BSD, and STAR tar utilities.
		file: "testdata/gnu-multi-hdrs.tar",
		headers: []*Header{{
			Name:     "GNU2/GNU2/long-path-name",
			Linkname: "GNU4/GNU4/long-linkpath-name",
			ModTime:  time.Unix(0, 0),

// and the GODEBUG environment variable contains `zipinsecurepath=0`,
// OpenReader returns the reader with an ErrInsecurePath error.
// A future version of Go may introduce this behavior by default.
// Programs that want to accept non-local names can ignore
// the ErrInsecurePath error and use the returned reader.
func OpenReader(name string) (*ReadCloser, error) {
	f, err := os.Open(name)
	if err != nil {

	STLXP	(R6, R11), (RSP), R6                             // ERROR "constrained unpredictable behavior"
	STXP	(R6, R11), (R2), R2                              // ERROR "constrained unpredictable behavior"
	STLXR	R3, (RSP), R3                                    // ERROR "constrained unpredictable behavior"
	STXR	R3, (R4), R4                                     // ERROR "constrained unpredictable behavior"

// untyped nil causes a run-time error (a different panic).
// The GODEBUG setting panicnil=1 disables the run-time error.
func panic(v any)

// The recover built-in function allows a program to manage behavior of a
// panicking goroutine. Executing a call to recover inside a deferred
// function (but not any function called by it) stops the panicking sequence
// by restoring normal execution and retrieves the error value passed to the

	}
	return 0, io.EOF
}

// Make sure that an empty Buffer remains empty when
// it is "grown" before a Read that panics
func TestReadFromPanicReader(t *testing.T) {

	// First verify non-panic behaviour
	var buf Buffer
	i, err := buf.ReadFrom(panicReader{})
	if err != nil {
		t.Fatal(err)
	}
	if i != 0 {
		t.Fatalf("unexpected return from bytes.ReadFrom (1): got: %d, want %d", i, 0)
	}

	// non-space bytes, so we're done. Non-ASCII cases have already
	// been handled above.
	if start == stop {
		// Special case to preserve previous TrimLeftFunc behavior,
		// returning nil instead of empty slice if all spaces.
		return nil
	}
	return s[start:stop]
}

// Runes interprets s as a sequence of UTF-8-encoded code points.

such as those in the <a href="/pkg/sync/"><code>sync</code></a>
and <a href="/pkg/sync/atomic/"><code>sync/atomic</code></a> packages.
</p>

<p>
If you must read the rest of this document to understand the behavior of your program,
you are being too clever.
</p>

<p>
Don't be clever.
</p>

<h3 id="overview">Informal Overview</h3>

<p>