// See https://golang.org/issue/23469.
	output, err := exec.Command(swig, "-go", "-swiglib").Output()
	if err != nil {
		t.Skip("swig is missing Go support")
	}
	swigDir := strings.TrimSpace(string(output))

	_, err = os.Stat(filepath.Join(swigDir, "go"))
	if err != nil {
		t.Skip("swig is missing Go support")
	}

	// Check that swig has a new enough version.
	// See https://golang.org/issue/22858.

		wanted := strings.Split(string(bs), "\n")
		sort.Strings(wanted)
		for _, feature := range wanted {
			if feature == "" {
				continue
			}
			_, ok := w.features[feature]
			if !ok {
				t.Errorf("package %s: missing feature %q", fi.Name(), feature)
			}
			delete(w.features, feature)
		}

		for _, feature := range w.Features() {
			t.Errorf("package %s: extra feature not in golden file: %q", fi.Name(), feature)
		}
	}
}

		return
	}
	for _, c := range n.Doc.List {
		if !strings.HasPrefix(c.Text, "//export ") {
			continue
		}

		name := strings.TrimSpace(c.Text[9:])
		if name == "" {
			error_(c.Pos(), "export missing name")
		}

		if name != n.Name.Name {
			error_(c.Pos(), "export comment has wrong name %q, want %q", name, n.Name.Name)
		}

		doc := ""
		for _, c1 := range n.Doc.List {
			if c1 != c {

</p>

<pre>
s[0] == 2
s[1] == 3
s[2] == 4
</pre>

<p>
For convenience, any of the indices may be omitted. A missing <code>low</code>
index defaults to zero; a missing <code>high</code> index defaults to the length of the
sliced operand:
</p>

<pre>
a[2:]  // same as a[2 : len(a)]
a[:3]  // same as a[0 : 3]
a[:]   // same as a[0 : len(a)]

	{"retlo+12(FP)", "retlo+12(FP)"},
	{"runtime·gogo(SB)", "runtime.gogo(SB)"},
	{"·AddUint32(SB)", "pkg.AddUint32(SB)"},
	{"(R1, R3)", "(R1, R3)"},
	{"[R0,R1,g,R15", ""}, // Issue 11764 - asm hung parsing ']' missing register lists.
	{"[):[o-FP", ""},     // Issue 12469 - there was no infinite loop for ARM; these are just sanity checks.
	{"[):[R0-FP", ""},
	{"(", ""}, // Issue 12466 - backed up before beginning of line.
}

is okay, because cmd/link also processes the cgo_import_static directive and
knows that _cgo_gcc_Cfunc_sin is expected to be supplied by a host
object file, so cmd/link does not treat the missing symbol as an error when
creating go.o. Indeed, the definition for _cgo_gcc_Cfunc_sin will be
provided to the host linker by foo2.cgo.o, which in turn will need the

	callbackMutex.Unlock()
}

//export goCallback
func goCallback(p unsafe.Pointer) {
	i := *(*int)(p)

	callbackMutex.Lock()
	f := callbackFuncs[i]
	callbackMutex.Unlock()

	if f == nil {
		panic("missing callback function")
	}
	f()
}

func testCallback(t *testing.T) {
	var x = false
	nestedCall(func() { x = true })
	if !x {
		t.Fatal("nestedCall did not call func")
	}
}

			"gid": "gtgergergersagersgers",
		},
		ok: false,
	}, {
		in: map[string]string{
			"missing":          "missing",
			"SCHILY.xattr.key": "value",
		},
		want: &Header{
			Xattrs: map[string]string{"key": "value"},
			PAXRecords: map[string]string{
				"missing":          "missing",
				"SCHILY.xattr.key": "value",
			},
		},
		ok: true,
	}}

	for i, v := range vectors {

	{"3>>(1<<63)", "negative right shift count"},
	{"(1<<63)>>2", "right shift of value with high bit set"},
	{"(1<<62)>>2", ""},
	{`'\x80'`, "illegal UTF-8 encoding for character constant"},
	{"(23*4", "missing closing paren"},
	{")23*4", "unexpected ) evaluating expression"},
	{"18446744073709551616", "value out of range"},
}

func TestBadExpr(t *testing.T) {
	for i, test := range badExprTests {

<p>
The assemblers are designed to support the compiler so not all hardware instructions
are defined for all architectures: if the compiler doesn't generate it, it might not be there.
If you need to use a missing instruction, there are two ways to proceed.
One is to update the assembler to support that instruction, which is straightforward
but only worthwhile if it's likely the instruction will be used again.