encoding/binary: reject types with implementation-dependent sizes

Fixes #1201.

R=rsc
CC=golang-dev
https://golang.org/cl/3787044

src/pkg/encoding/binary/binary.go

@@ -198,6 +198,10 @@ func sizeof(v reflect.Type) int {
 		return sum
 
 	case *reflect.UintType, *reflect.IntType, *reflect.FloatType, *reflect.ComplexType:
+		switch t := t.Kind(); t {
+		case reflect.Int, reflect.Uint, reflect.Uintptr, reflect.Float, reflect.Complex:
+			return -1
+		}
 		return int(v.Size())
 	}
 	return -1

src/pkg/encoding/binary/binary_test.go

@@ -28,6 +28,15 @@ type Struct struct {
 	Array      [4]uint8
 }
 
+type T struct {
+	Int     int
+	Uint    uint
+	Float   float
+	Complex complex
+	Uintptr uintptr
+	Array   [4]int
+}
+
 var s = Struct{
 	0x01,
 	0x0203,
@@ -136,3 +145,20 @@ func TestWriteSlice(t *testing.T) {
 	err := Write(buf, BigEndian, res)
 	checkResult(t, "WriteSlice", BigEndian, err, buf.Bytes(), src)
 }
+
+func TestWriteT(t *testing.T) {
+	buf := new(bytes.Buffer)
+	ts := T{}
+	err := Write(buf, BigEndian, ts)
+	if err == nil {
+		t.Errorf("WriteT: have nil, want non-nil")
+	}
+
+	tv := reflect.Indirect(reflect.NewValue(ts)).(*reflect.StructValue)
+	for i, n := 0, tv.NumField(); i < n; i++ {
+		err = Write(buf, BigEndian, tv.Field(i).Interface())
+		if err == nil {
+			t.Errorf("WriteT.%v: have nil, want non-nil", tv.Field(i).Type())
+		}
+	}
+}