reflect: test name data is aligned

For #14962.

Change-Id: I3539d882487c99dee99ac953e039b79c6b963cf9
Reviewed-on: https://go-review.googlesource.com/21150
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/reflect/all_test.go

@@ -5065,3 +5065,16 @@ func TestNames(t *testing.T) {
 		}
 	}
 }
+
+type embed struct {
+	EmbedWithUnexpMeth
+}
+
+func TestNameBytesAreAligned(t *testing.T) {
+	typ := TypeOf(embed{})
+	b := FirstMethodNameBytes(typ)
+	v := uintptr(unsafe.Pointer(b))
+	if v%unsafe.Alignof((*byte)(nil)) != 0 {
+		t.Errorf("reflect.name.bytes pointer is not aligned: %x", v)
+	}
+}

src/reflect/export_test.go

@@ -70,3 +70,27 @@ func CachedBucketOf(m Type) Type {
 	tt := (*mapType)(unsafe.Pointer(t))
 	return tt.bucket
 }
+
+type EmbedWithUnexpMeth struct{}
+
+func (EmbedWithUnexpMeth) f() {}
+
+type pinUnexpMeth interface {
+	f()
+}
+
+var pinUnexpMethI = pinUnexpMeth(EmbedWithUnexpMeth{})
+
+func FirstMethodNameBytes(t Type) *byte {
+	_ = pinUnexpMethI
+
+	ut := t.uncommon()
+	if ut == nil {
+		panic("type has no methods")
+	}
+	m := ut.methods[0]
+	if *m.name.data(0)&(1<<2) == 0 {
+		panic("method name does not have pkgPath *string")
+	}
+	return m.name.bytes
+}