log.Printf(" url %s has #%s", url, id)
		}
		fragExists[urlFrag{url, id}] = true
	}
	return nil
}

func main() {
	flag.Parse()

	go crawlLoop()
	crawl(*root, "")

	wg.Wait()
	close(urlq)
	for uf, needers := range neededFrags {
		if !fragExists[uf] {
			problems = append(problems, fmt.Sprintf("Missing fragment for %+v from %v", uf, needers))
		}
	}

pkg syscall (freebsd-riscv64), const SYS_KSEM_UNLINK = 406 #53466
pkg syscall (freebsd-riscv64), const SYS_KSEM_UNLINK ideal-int #53466
pkg syscall (freebsd-riscv64), const SYS_KSEM_WAIT = 402 #53466
pkg syscall (freebsd-riscv64), const SYS_KSEM_WAIT ideal-int #53466
pkg syscall (freebsd-riscv64), const SYS_KTIMER_CREATE = 235 #53466
pkg syscall (freebsd-riscv64), const SYS_KTIMER_CREATE ideal-int #53466

				time.Sleep(time.Millisecond)
				continue
			}

			t.Error(err)
			return
		}
		cmds = append(cmds, cmd)
	}

	failures := 0
	for _, cmd := range cmds {
		err := cmd.Wait()
		if err == nil {
			continue
		}

		t.Errorf("syscall.Exec failed: %v\n%s", err, cmd.Stdout)
		failures++
	}

	if failures > 0 {
		t.Logf("Failed %v of %v attempts.", failures, len(cmds))

	for _, context := range contexts {
		context := context
		wg.Add(1)
		go func() {
			defer wg.Done()
			_ = NewWalker(context, filepath.Join(testenv.GOROOT(nil), "src"))
		}()
	}
	wg.Wait()
})

func TestIssue21181(t *testing.T) {
	if testing.Short() {
		t.Skip("skipping with -short")
	}
	if *flagCheck {
		// slow, not worth repeating in -check
		t.Skip("skipping with -check set")

linkage to the desired libraries. The main function is provided by
_cgo_main.c:

	int main() { return 0; }
	void crosscall2(void(*fn)(void*), void *a, int c, uintptr_t ctxt) { }
	uintptr_t _cgo_wait_runtime_init_done(void) { return 0; }
	void _cgo_release_context(uintptr_t ctxt) { }
	char* _cgo_topofstack(void) { return (char*)0; }
	void _cgo_allocate(void *a, int c) { }
	void _cgo_panic(void *a, int c) { }

immediately, yielding the element type's <a href="#The_zero_value">zero value</a>
after any previously sent values have been received.
</p>

<pre>
v1 := &lt;-ch
v2 = &lt;-ch
f(&lt;-ch)
&lt;-strobe  // wait until clock pulse and discard received value
</pre>

<p>
A receive expression used in an <a href="#Assignments">assignment</a> or initialization of the special form
</p>

<pre>
x, ok = &lt;-ch

pkg syscall (netbsd-arm64-cgo), const SYS__LWP_UNPARK_ALL ideal-int
pkg syscall (netbsd-arm64-cgo), const SYS__LWP_UNPARK ideal-int
pkg syscall (netbsd-arm64-cgo), const SYS__LWP_WAIT = 312
pkg syscall (netbsd-arm64-cgo), const SYS__LWP_WAIT ideal-int
pkg syscall (netbsd-arm64-cgo), const SYS__LWP_WAKEUP = 315
pkg syscall (netbsd-arm64-cgo), const SYS__LWP_WAKEUP ideal-int
pkg syscall (netbsd-arm64-cgo), const SYS_MADVISE = 75

pkg syscall (windows-386), const USAGE_MATCH_TYPE_OR ideal-int
pkg syscall (windows-386), const WAIT_ABANDONED ideal-int
pkg syscall (windows-386), const WAIT_FAILED ideal-int
pkg syscall (windows-386), const WAIT_OBJECT_0 ideal-int
pkg syscall (windows-386), const WAIT_TIMEOUT ideal-int
pkg syscall (windows-386), const WSADESCRIPTION_LEN ideal-int

pkg syscall (darwin-arm64), const SYS_SEM_UNLINK ideal-int
pkg syscall (darwin-arm64), const SYS_SEM_WAIT = 271
pkg syscall (darwin-arm64), const SYS_SEM_WAIT ideal-int
pkg syscall (darwin-arm64), const SYS_SEM_WAIT_NOCANCEL = 420
pkg syscall (darwin-arm64), const SYS_SEM_WAIT_NOCANCEL ideal-int
pkg syscall (darwin-arm64), const SYS_SENDFILE = 337
pkg syscall (darwin-arm64), const SYS_SENDFILE ideal-int

pkg syscall (freebsd-arm64), const SYS_KSEM_UNLINK = 406
pkg syscall (freebsd-arm64), const SYS_KSEM_UNLINK ideal-int
pkg syscall (freebsd-arm64), const SYS_KSEM_WAIT = 402
pkg syscall (freebsd-arm64), const SYS_KSEM_WAIT ideal-int
pkg syscall (freebsd-arm64), const SYS_KTIMER_CREATE = 235
pkg syscall (freebsd-arm64), const SYS_KTIMER_CREATE ideal-int
pkg syscall (freebsd-arm64), const SYS_KTIMER_DELETE = 236