func (v *Variable) setValue(y *Variable) error {
	var err error
	switch v.Kind {
	case reflect.Float32, reflect.Float64:
		f, _ := constant.Float64Val(y.Value)
		err = v.writeFloatRaw(f, v.RealType.Size())
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		n, _ := constant.Int64Val(y.Value)
		err = v.writeUint(uint64(n), v.RealType.Size())
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		n, _ := constant.Uint64Val(y.Value)
		err = v.writeUint(n, v.RealType.Size())
	case reflect.Bool:
		err = v.writeBool(constant.BoolVal(y.Value))
	case reflect.Complex64, reflect.Complex128:
		real, _ := constant.Float64Val(constant.Real(y.Value))
		imag, _ := constant.Float64Val(constant.Imag(y.Value))
		err = v.writeComplex(real, imag, v.RealType.Size())
	default:
		fmt.Printf("default\n")
		if t, isptr := v.RealType.(*dwarf.PtrType); isptr {
			err = v.writeUint(uint64(y.Children[0].Addr), int64(t.ByteSize))
		} else {
			return fmt.Errorf("can not set variables of type %s (not implemented)", v.Kind.String())
		}
	}

	return err
}

func (p *exporter) value(x constant.Value) {
	if trace {
		p.tracef("value { ")
		defer p.tracef("} ")
	}

	switch kind := x.Kind(); kind {
	case constant.Bool:
		tag := falseTag
		if constant.BoolVal(x) {
			tag = trueTag
		}
		p.int(tag)
	case constant.Int:
		if i, ok := constant.Int64Val(x); ok {
			p.int(int64Tag)
			p.int64(i)
			return
		}
		p.int(floatTag)
		p.float(x)
	case constant.Float:
		p.int(fractionTag)
		p.fraction(x)
	case constant.Complex:
		p.int(complexTag)
		p.fraction(constant.Real(x))
		p.fraction(constant.Imag(x))
	case constant.String:
		p.int(stringTag)
		p.string(constant.StringVal(x))
	default:
		panic(fmt.Sprintf("unexpected value kind %d", kind))
	}
}

func BoolValue(expr ast.Expr, info *types.Info) (bool, bool) {
	v := info.Types[expr].Value
	if v != nil && v.Kind() == constant.Bool {
		return constant.BoolVal(v), true
	}
	switch e := expr.(type) {
	case *ast.BinaryExpr:
		switch e.Op {
		case token.LAND:
			if b, ok := BoolValue(e.X, info); ok {
				if !b {
					return false, true
				}
				return BoolValue(e.Y, info)
			}
		case token.LOR:
			if b, ok := BoolValue(e.X, info); ok {
				if b {
					return true, true
				}
				return BoolValue(e.Y, info)
			}
		}
	case *ast.UnaryExpr:
		if e.Op == token.NOT {
			if b, ok := BoolValue(e.X, info); ok {
				return !b, true
			}
		}
	case *ast.ParenExpr:
		return BoolValue(e.X, info)
	}
	return false, false
}

// constValue returns the value of the constant with the
// dynamic type tag appropriate for c.Type().
func constValue(c *ssa.Const) value {
	if c.IsNil() {
		return zero(c.Type()) // typed nil
	}

	if t, ok := c.Type().Underlying().(*types.Basic); ok {
		// TODO(adonovan): eliminate untyped constants from SSA form.
		switch t.Kind() {
		case types.Bool, types.UntypedBool:
			return exact.BoolVal(c.Value)
		case types.Int, types.UntypedInt:
			// Assume sizeof(int) is same on host and target.
			return int(c.Int64())
		case types.Int8:
			return int8(c.Int64())
		case types.Int16:
			return int16(c.Int64())
		case types.Int32, types.UntypedRune:
			return int32(c.Int64())
		case types.Int64:
			return c.Int64()
		case types.Uint:
			// Assume sizeof(uint) is same on host and target.
			return uint(c.Uint64())
		case types.Uint8:
			return uint8(c.Uint64())
		case types.Uint16:
			return uint16(c.Uint64())
		case types.Uint32:
			return uint32(c.Uint64())
		case types.Uint64:
			return c.Uint64()
		case types.Uintptr:
			// Assume sizeof(uintptr) is same on host and target.
			return uintptr(c.Uint64())
		case types.Float32:
			return float32(c.Float64())
		case types.Float64, types.UntypedFloat:
			return c.Float64()
		case types.Complex64:
			return complex64(c.Complex128())
		case types.Complex128, types.UntypedComplex:
			return c.Complex128()
		case types.String, types.UntypedString:
			if c.Value.Kind() == exact.String {
				return exact.StringVal(c.Value)
			}
			return string(rune(c.Int64()))
		}
	}

	panic(fmt.Sprintf("constValue: %s", c))
}

func (g *ObjcGen) genConstM(o *types.Const) {
	if _, ok := o.Type().(*types.Basic); !ok {
		g.Printf("// skipped const %s with unsupported type: %T\n\n", o.Name(), o)
		return
	}
	cName := fmt.Sprintf("%s%s", g.namePrefix, o.Name())
	objcType := g.objcType(o.Type())

	switch b := o.Type().(*types.Basic); b.Kind() {
	case types.Bool, types.UntypedBool:
		v := "NO"
		if constant.BoolVal(o.Val()) {
			v = "YES"
		}
		g.Printf("const BOOL %s = %s;\n", cName, v)

	case types.String, types.UntypedString:
		g.Printf("NSString* const %s = @%s;\n", cName, constExactString(o))

	case types.Int, types.Int8, types.Int16, types.Int32:
		g.Printf("const %s %s = %s;\n", objcType, cName, o.Val())

	case types.Int64, types.UntypedInt:
		i, exact := constant.Int64Val(o.Val())
		if !exact {
			g.errorf("const value %s for %s cannot be represented as %s", o.Val(), o.Name(), objcType)
			return
		}
		if i == math.MinInt64 {
			// -9223372036854775808LL does not work because 922337203685477508 is
			// larger than max int64.
			g.Printf("const int64_t %s = %dLL-1;\n", cName, i+1)
		} else {
			g.Printf("const int64_t %s = %dLL;\n", cName, i)
		}

	case types.Float32, types.Float64, types.UntypedFloat:
		f, _ := constant.Float64Val(o.Val())
		if math.IsInf(f, 0) || math.Abs(f) > math.MaxFloat64 {
			g.errorf("const value %s for %s cannot be represented as double", o.Val(), o.Name())
			return
		}
		g.Printf("const %s %s = %g;\n", objcType, cName, f)

	default:
		g.errorf("unsupported const type %s for %s", b, o.Name())
	}
}

func (p *exporter) value(x constant.Value) {
	if trace {
		p.tracef("= ")
	}

	switch x.Kind() {
	case constant.Bool:
		tag := falseTag
		if constant.BoolVal(x) {
			tag = trueTag
		}
		p.tag(tag)

	case constant.Int:
		if v, exact := constant.Int64Val(x); exact {
			// common case: x fits into an int64 - use compact encoding
			p.tag(int64Tag)
			p.int64(v)
			return
		}
		// uncommon case: large x - use float encoding
		// (powers of 2 will be encoded efficiently with exponent)
		p.tag(floatTag)
		p.float(constant.ToFloat(x))

	case constant.Float:
		p.tag(floatTag)
		p.float(x)

	case constant.Complex:
		p.tag(complexTag)
		p.float(constant.Real(x))
		p.float(constant.Imag(x))

	case constant.String:
		p.tag(stringTag)
		p.string(constant.StringVal(x))

	case constant.Unknown:
		// package contains type errors
		p.tag(unknownTag)

	default:
		log.Fatalf("gcimporter: unexpected value %v (%T)", x, x)
	}
}

func (bp *Breakpoint) checkCondition(thread *Thread) (bool, error) {
	if bp.Cond == nil {
		return true, nil
	}
	scope, err := thread.Scope()
	if err != nil {
		return true, err
	}
	v, err := scope.evalAST(bp.Cond)
	if err != nil {
		return true, fmt.Errorf("error evaluating expression: %v", err)
	}
	if v.Unreadable != nil {
		return true, fmt.Errorf("condition expression unreadable: %v", v.Unreadable)
	}
	if v.Kind != reflect.Bool {
		return true, errors.New("condition expression not boolean")
	}
	return constant.BoolVal(v.Value), nil
}

func (c *converter) convertConstantValue(v goconstant.Value) constant.Value {
	if v == nil {
		return nil
	}
	if v, ok := c.converted[v]; ok {
		return v.(constant.Value)
	}
	var ret constant.Value
	switch v.Kind() {
	case goconstant.Bool:
		ret = constant.MakeBool(goconstant.BoolVal(v))
	case goconstant.String:
		ret = constant.MakeString(goconstant.StringVal(v))
	case goconstant.Int:
		ret = constant.MakeFromLiteral(v.String(), token.INT, 0)
	case goconstant.Float:
		ret = constant.MakeFromLiteral(v.String(), token.FLOAT, 0)
	case goconstant.Complex:
		ret = constant.MakeFromLiteral(v.String(), token.IMAG, 0)
	}
	c.converted[v] = ret
	return ret
}

//.........这里部分代码省略.........
		// unsafe.Offsetof(x T) uintptr, where x must be a selector
		// (no argument evaluated yet)
		arg0 := call.Args[0]
		selx, _ := unparen(arg0).(*ast.SelectorExpr)
		if selx == nil {
			check.invalidArg(arg0.Pos(), "%s is not a selector expression", arg0)
			check.use(arg0)
			return
		}

		check.expr(x, selx.X)
		if x.mode == invalid {
			return
		}

		base := derefStructPtr(x.typ)
		sel := selx.Sel.Name
		obj, index, indirect := LookupFieldOrMethod(base, false, check.pkg, sel)
		switch obj.(type) {
		case nil:
			check.invalidArg(x.pos(), "%s has no single field %s", base, sel)
			return
		case *Func:
			// TODO(gri) Using derefStructPtr may result in methods being found
			// that don't actually exist. An error either way, but the error
			// message is confusing. See: https://play.golang.org/p/al75v23kUy ,
			// but go/types reports: "invalid argument: x.m is a method value".
			check.invalidArg(arg0.Pos(), "%s is a method value", arg0)
			return
		}
		if indirect {
			check.invalidArg(x.pos(), "field %s is embedded via a pointer in %s", sel, base)
			return
		}

		// TODO(gri) Should we pass x.typ instead of base (and indirect report if derefStructPtr indirected)?
		check.recordSelection(selx, FieldVal, base, obj, index, false)

		offs := check.conf.offsetof(base, index)
		x.mode = constant_
		x.val = constant.MakeInt64(offs)
		x.typ = Typ[Uintptr]
		// result is constant - no need to record signature

	case _Sizeof:
		// unsafe.Sizeof(x T) uintptr
		check.assignment(x, nil, "argument to unsafe.Sizeof")
		if x.mode == invalid {
			return
		}

		x.mode = constant_
		x.val = constant.MakeInt64(check.conf.sizeof(x.typ))
		x.typ = Typ[Uintptr]
		// result is constant - no need to record signature

	case _Assert:
		// assert(pred) causes a typechecker error if pred is false.
		// The result of assert is the value of pred if there is no error.
		// Note: assert is only available in self-test mode.
		if x.mode != constant_ || !isBoolean(x.typ) {
			check.invalidArg(x.pos(), "%s is not a boolean constant", x)
			return
		}
		if x.val.Kind() != constant.Bool {
			check.errorf(x.pos(), "internal error: value of %s should be a boolean constant", x)
			return
		}
		if !constant.BoolVal(x.val) {
			check.errorf(call.Pos(), "%s failed", call)
			// compile-time assertion failure - safe to continue
		}
		// result is constant - no need to record signature

	case _Trace:
		// trace(x, y, z, ...) dumps the positions, expressions, and
		// values of its arguments. The result of trace is the value
		// of the first argument.
		// Note: trace is only available in self-test mode.
		// (no argument evaluated yet)
		if nargs == 0 {
			check.dump("%s: trace() without arguments", call.Pos())
			x.mode = novalue
			break
		}
		var t operand
		x1 := x
		for _, arg := range call.Args {
			check.rawExpr(x1, arg, nil) // permit trace for types, e.g.: new(trace(T))
			check.dump("%s: %s", x1.pos(), x1)
			x1 = &t // use incoming x only for first argument
		}
		// trace is only available in test mode - no need to record signature

	default:
		unreachable()
	}

	return true
}

func (c *funcContext) translateExpr(expr ast.Expr) *expression {
	exprType := c.p.TypeOf(expr)
	if value := c.p.Types[expr].Value; value != nil {
		basic := exprType.Underlying().(*types.Basic)
		switch {
		case isBoolean(basic):
			return c.formatExpr("%s", strconv.FormatBool(constant.BoolVal(value)))
		case isInteger(basic):
			if is64Bit(basic) {
				if basic.Kind() == types.Int64 {
					d, ok := constant.Int64Val(constant.ToInt(value))
					if !ok {
						panic("could not get exact uint")
					}
					return c.formatExpr("new %s(%s, %s)", c.typeName(exprType), strconv.FormatInt(d>>32, 10), strconv.FormatUint(uint64(d)&(1<<32-1), 10))
				}
				d, ok := constant.Uint64Val(constant.ToInt(value))
				if !ok {
					panic("could not get exact uint")
				}
				return c.formatExpr("new %s(%s, %s)", c.typeName(exprType), strconv.FormatUint(d>>32, 10), strconv.FormatUint(d&(1<<32-1), 10))
			}
			d, ok := constant.Int64Val(constant.ToInt(value))
			if !ok {
				panic("could not get exact int")
			}
			return c.formatExpr("%s", strconv.FormatInt(d, 10))
		case isFloat(basic):
			f, _ := constant.Float64Val(value)
			return c.formatExpr("%s", strconv.FormatFloat(f, 'g', -1, 64))
		case isComplex(basic):
			r, _ := constant.Float64Val(constant.Real(value))
			i, _ := constant.Float64Val(constant.Imag(value))
			if basic.Kind() == types.UntypedComplex {
				exprType = types.Typ[types.Complex128]
			}
			return c.formatExpr("new %s(%s, %s)", c.typeName(exprType), strconv.FormatFloat(r, 'g', -1, 64), strconv.FormatFloat(i, 'g', -1, 64))
		case isString(basic):
			return c.formatExpr("%s", encodeString(constant.StringVal(value)))
		default:
			panic("Unhandled constant type: " + basic.String())
		}
	}

	var obj types.Object
	switch e := expr.(type) {
	case *ast.SelectorExpr:
		obj = c.p.Uses[e.Sel]
	case *ast.Ident:
		obj = c.p.Defs[e]
		if obj == nil {
			obj = c.p.Uses[e]
		}
	}

	if obj != nil && typesutil.IsJsPackage(obj.Pkg()) {
		switch obj.Name() {
		case "Global":
			return c.formatExpr("$global")
		case "Module":
			return c.formatExpr("$module")
		case "Undefined":
			return c.formatExpr("undefined")
		}
	}

	switch e := expr.(type) {
	case *ast.CompositeLit:
		if ptrType, isPointer := exprType.(*types.Pointer); isPointer {
			exprType = ptrType.Elem()
		}

		collectIndexedElements := func(elementType types.Type) []string {
			var elements []string
			i := 0
			zero := c.translateExpr(c.zeroValue(elementType)).String()
			for _, element := range e.Elts {
				if kve, isKve := element.(*ast.KeyValueExpr); isKve {
					key, ok := constant.Int64Val(constant.ToInt(c.p.Types[kve.Key].Value))
					if !ok {
						panic("could not get exact int")
					}
					i = int(key)
					element = kve.Value
				}
				for len(elements) <= i {
					elements = append(elements, zero)
				}
				elements[i] = c.translateImplicitConversionWithCloning(element, elementType).String()
				i++
			}
			return elements
		}

		switch t := exprType.Underlying().(type) {
		case *types.Array:
			elements := collectIndexedElements(t.Elem())
			if len(elements) == 0 {
				return c.formatExpr("%s.zero()", c.typeName(t))
			}
//.........这里部分代码省略.........