if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
	if err := json.Unmarshal(b1, &t1); err != nil  {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}

	var t2 time.Time
	b2, err := os.ReadFile(os.Args[2])
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
	if err := json.Unmarshal(b2, &t2); err != nil  {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}

env GOTOOLCHAIN=go1.9999x
! go version
stderr 'go: download go1.9999x for .*: toolchain not available'

# GOTOOLCHAIN from network
[!exec:/bin/sh] stop 'the fake proxy serves shell scripts instead of binaries'
env GOTOOLCHAIN=go1.999testmod
go version
stderr 'go: downloading go1.999testmod \(.*/.*\)'

# GOTOOLCHAIN cached from network
go version
! stderr downloading
stdout go1.999testmod

	out, err := cmd.CombinedOutput()
	if err != nil {
		fmt.Fprintf(os.Stderr, "%s env GOROOT: %v, %s\n", exe, err, out)
		os.Exit(1)
	}
	goroot, err := filepath.EvalSymlinks(strings.TrimSpace(string(out)))
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
	want, err = filepath.EvalSymlinks(want)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
	if !strings.EqualFold(goroot, want) {

stderr 'compile( |\.exe"?)'
stderr 'main.go:2.* can inline main' # from compiler
stderr 'link(\.exe"?)? -'
stderr '\d+ symbols' # from linker

# ... but not the second, even though it still prints the compiler and linker output.
go build -x -gcflags=-m -ldflags='-v -w' main.go
! stderr 'compile( |\.exe"?)'
stderr 'main.go:2.* can inline main' # from compiler
! stderr 'link(\.exe"?)? -'
stderr '\d+ symbols' # from linker

	if (i != 0) {
		fprintf(stderr, "pthread_join: %s\n", strerror(i));
		exit(EXIT_FAILURE);
	}

	i = pthread_create(&tid, NULL, thread2, NULL);
	if (i != 0) {
		fprintf(stderr, "pthread_create: %s\n", strerror(i));
		exit(EXIT_FAILURE);
	}

	i = pthread_join(tid, NULL);
	if (i != 0) {
		fprintf(stderr, "pthread_join: %s\n", strerror(i));
		exit(EXIT_FAILURE);
	}

	if (!ok) {

go build -a -n -v -gcflags=-e z1 z2
stderr 'compile.* -p z1.* -e '
stderr 'compile.* -p z2.* -e '
stderr 'compile.* -p y'
! stderr 'compile.* -p [^z].* -e '

# -gcflags can specify package=flags, and can be repeated; last match wins
go build -a -n -v -gcflags=-e -gcflags=z1=-N z1 z2
stderr 'compile.* -p z1.* -N '
! stderr 'compile.* -p z1.* -e '
! stderr 'compile.* -p z2.* -N '
stderr 'compile.* -p z2.* -e '
stderr 'compile.* -p y'

	}
}

func warn(s string, a ...interface{}) {
	fmt.Fprintf(os.Stderr, "warning: ")
	fmt.Fprintf(os.Stderr, s, a...)
	fmt.Fprintf(os.Stderr, "\n")
	if *hwflag {
		panic("unexpected warning")
	}
}

func fatal(s string, a ...interface{}) {
	fmt.Fprintf(os.Stderr, "error: ")
	fmt.Fprintf(os.Stderr, s, a...)
	fmt.Fprintf(os.Stderr, "\n")
	if *hflag {
		panic("fatal error")
	}
	Exit(1)
}

env GOENV=badenv
env GOOS=
env GOARCH=
env GOEXPERIMENT=

! go env
stderr '^go(\.exe)?: unknown GOEXPERIMENT badexp$'

go env -u GOEXPERIMENT

! go env
stderr '^go: unsupported GOOS/GOARCH pair bados/badarch$'

! go env -u GOOS
stderr '^go: unsupported GOOS/GOARCH pair \w+/badarch$'

! go env -u GOARCH
stderr '^go: unsupported GOOS/GOARCH pair bados/\w+$'

go env -u GOOS GOARCH

go env

stderr 'package command-line-arguments: invalid package directory .*uh-oh'

go run .
! stdout panic
! stderr panic
stderr '^ok$'

[cgo] go run main.go
[!cgo] go run main_nocgo.go
! stdout panic
! stderr panic
stderr '^ok$'

go test -v
! stdout panic
! stderr panic
stdout '^ok$'  # 'go test' combines the test's stdout into stderr

go test -v .
! stdout panic
! stderr panic

# 'go get' should update the main module's go.mod file to a version compatible with the
# go version required for rsc.io/future, not fail.
go get .
stderr '^go: module rsc.io/future@v1.0.0 requires go >= 1.999; switching to go1.999testmod$'
stderr '^go: upgraded go 1.21 => 1.999$'
stderr '^go: added toolchain go1.999testmod$'


# Now, the various 'go mod' subcommands should succeed.

go mod download

go mod verify