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 {
					_ = md5.Sum([]byte("Hello, !"))
				}
			}()

When using cgo, Go must not assume that it owns all details of the
process. In particular it needs to coordinate with C in the use of
threads and thread-local storage. The runtime package declares a few
variables:

	var (
		iscgo             bool
		_cgo_init         unsafe.Pointer
		_cgo_thread_start unsafe.Pointer
	)

Any package using cgo imports "runtime/cgo", which provides

	buf := make([]byte, 1)
	if _, err := b.Read(nil); err != nil {
		t.Fatalf("1st nil Read = %v; want nil", err)
	}
	if _, err := b.Read(buf); err != errFake {
		t.Fatalf("1st Read = %v; want errFake", err)
	}
	if _, err := b.Read(nil); err != nil {
		t.Fatalf("2nd nil Read = %v; want nil", err)
	}
	if _, err := b.Read(buf); err != nil {
		t.Fatalf("3rd Read with buffer = %v; want nil", err)
	}

	if lockedOSThread() {
		t.Fatal("locked OS thread on entry to TestCallbackPanic")
	}
	defer func() {
		s := recover()
		if s == nil {
			t.Fatal("did not panic")
		}
		if s.(string) != "callback panic" {
			t.Fatal("wrong panic:", s)
		}
		if lockedOSThread() {
			t.Fatal("locked OS thread on exit from TestCallbackPanic")
		}
	}()
	nestedCall(func() { panic("callback panic") })

<code>T</code>’s embedded interfaces.
</p>

<pre>
type Reader interface {
	Read(p []byte) (n int, err error)
	Close() error
}

type Writer interface {
	Write(p []byte) (n int, err error)
	Close() error
}

// ReadWriter's methods are Read, Write, and Close.
type ReadWriter interface {
	Reader  // includes methods of Reader in ReadWriter's method set

//   int i;
//   nts = argc;
//   t = calloc(nts, sizeof(pthread_t));
//   pthread_mutex_init(&mu, NULL);
//   for (i = 0; i < nts; i++) {
//     pthread_create(&t[i], NULL, aFn, NULL);
//   }
// }
//
// void cleanup(void) {
//   int i;
//   pthread_mutex_lock(&mu);
//   all_done = 1;
//   pthread_mutex_unlock(&mu);
//   for (i = 0; i < nts; i++) {
//     pthread_join(t[i], NULL);
//   }
//   pthread_mutex_destroy(&mu);

}

var errUnreadByte = errors.New("bytes.Buffer: UnreadByte: previous operation was not a successful read")

// UnreadByte unreads the last byte returned by the most recent successful
// read operation that read at least one byte. If a write has happened since
// the last read, if the last read returned an error, or if the read read zero
// bytes, UnreadByte returns an error.
func (b *Buffer) UnreadByte() error {

pkg syscall (darwin-arm64), const SYS___PTHREAD_CANCELED = 333
pkg syscall (darwin-arm64), const SYS___PTHREAD_CANCELED ideal-int
pkg syscall (darwin-arm64), const SYS___PTHREAD_CHDIR = 348
pkg syscall (darwin-arm64), const SYS___PTHREAD_CHDIR ideal-int
pkg syscall (darwin-arm64), const SYS___PTHREAD_FCHDIR = 349
pkg syscall (darwin-arm64), const SYS___PTHREAD_FCHDIR ideal-int

pkg debug/macho, type SymtabCmd struct, Strsize uint32
pkg debug/macho, type SymtabCmd struct, Symoff uint32
pkg debug/macho, type Thread struct
pkg debug/macho, type Thread struct, Cmd LoadCmd
pkg debug/macho, type Thread struct, Data []uint32
pkg debug/macho, type Thread struct, Len uint32
pkg debug/macho, type Thread struct, Type uint32
pkg debug/macho, type Type uint32
pkg debug/pe, const IMAGE_FILE_MACHINE_AM33 ideal-int

pkg syscall (freebsd-arm64), const RUSAGE_SELF = 0
pkg syscall (freebsd-arm64), const RUSAGE_SELF ideal-int
pkg syscall (freebsd-arm64), const RUSAGE_THREAD = 1
pkg syscall (freebsd-arm64), const RUSAGE_THREAD ideal-int
pkg syscall (freebsd-arm64), const S_IFMT = 61440
pkg syscall (freebsd-arm64), const S_IRWXG = 56
pkg syscall (freebsd-arm64), const S_IRWXG ideal-int