From adf9b30e55943feb44669ebf773964fd32d4ee94 Mon Sep 17 00:00:00 2001
From: Marcel van Lohuizen <mpvl@golang.org>
Date: Fri, 28 Aug 2015 09:33:51 +0200
Subject: [PATCH] reflect: adjust access to unexported embedded structs

This CL changes reflect to allow access to exported fields and
methods in unexported embedded structs for gccgo and after gc
has been adjusted to disallow access to embedded unexported structs.

Adresses #12367, #7363, #11007, and #7247.

Change-Id: If80536eab35abcd25300d8ddc2d27d5c42d7e78e
Reviewed-on: https://go-review.googlesource.com/14010
Reviewed-by: Russ Cox <rsc@golang.org>
---
 src/reflect/export_test.go |  4 ++--
 src/reflect/type.go        |  2 +-
 src/reflect/value.go       | 27 +++++++++++++++++----------
 3 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/src/reflect/export_test.go b/src/reflect/export_test.go
index 0b9d0fde9e..26a648e193 100644
--- a/src/reflect/export_test.go
+++ b/src/reflect/export_test.go
@@ -8,13 +8,13 @@ import "unsafe"
 
 // MakeRO returns a copy of v with the read-only flag set.
 func MakeRO(v Value) Value {
-	v.flag |= flagRO
+	v.flag |= flagStickyRO
 	return v
 }
 
 // IsRO reports whether v's read-only flag is set.
 func IsRO(v Value) bool {
-	return v.flag&flagRO != 0
+	return v.flag&flagStickyRO != 0
 }
 
 var CallGC = &callGC
diff --git a/src/reflect/type.go b/src/reflect/type.go
index e98c960a03..aa56fcbe95 100644
--- a/src/reflect/type.go
+++ b/src/reflect/type.go
@@ -496,7 +496,7 @@ func (t *uncommonType) Method(i int) (m Method) {
 	fl := flag(Func)
 	if p.pkgPath != nil {
 		m.PkgPath = *p.pkgPath
-		fl |= flagRO
+		fl |= flagStickyRO
 	}
 	mt := p.typ
 	m.Type = mt
diff --git a/src/reflect/value.go b/src/reflect/value.go
index 001d0274ec..2317a7bec3 100644
--- a/src/reflect/value.go
+++ b/src/reflect/value.go
@@ -44,7 +44,8 @@ type Value struct {
 
 	// flag holds metadata about the value.
 	// The lowest bits are flag bits:
-	//	- flagRO: obtained via unexported field, so read-only
+	//	- flagStickyRO: obtained via unexported not embedded field, so read-only
+	//	- flagEmbedRO: obtained via unexported embedded field, so read-only
 	//	- flagIndir: val holds a pointer to the data
 	//	- flagAddr: v.CanAddr is true (implies flagIndir)
 	//	- flagMethod: v is a method value.
@@ -67,11 +68,13 @@ type flag uintptr
 const (
 	flagKindWidth        = 5 // there are 27 kinds
 	flagKindMask    flag = 1<<flagKindWidth - 1
-	flagRO          flag = 1 << 5
-	flagIndir       flag = 1 << 6
-	flagAddr        flag = 1 << 7
-	flagMethod      flag = 1 << 8
-	flagMethodShift      = 9
+	flagStickyRO    flag = 1 << 5
+	flagEmbedRO     flag = 1 << 6
+	flagIndir       flag = 1 << 7
+	flagAddr        flag = 1 << 8
+	flagMethod      flag = 1 << 9
+	flagMethodShift      = 10
+	flagRO          flag = flagStickyRO | flagEmbedRO
 )
 
 func (f flag) kind() Kind {
@@ -745,11 +748,15 @@ func (v Value) Field(i int) Value {
 	field := &tt.fields[i]
 	typ := field.typ
 
-	// Inherit permission bits from v.
-	fl := v.flag&(flagRO|flagIndir|flagAddr) | flag(typ.Kind())
+	// Inherit permission bits from v, but clear flagEmbedRO.
+	fl := v.flag&(flagStickyRO|flagIndir|flagAddr) | flag(typ.Kind())
 	// Using an unexported field forces flagRO.
 	if field.pkgPath != nil {
-		fl |= flagRO
+		if field.name == nil {
+			fl |= flagEmbedRO
+		} else {
+			fl |= flagStickyRO
+		}
 	}
 	// Either flagIndir is set and v.ptr points at struct,
 	// or flagIndir is not set and v.ptr is the actual struct data.
@@ -1104,7 +1111,7 @@ func (v Value) Method(i int) Value {
 	if v.typ.Kind() == Interface && v.IsNil() {
 		panic("reflect: Method on nil interface value")
 	}
-	fl := v.flag & (flagRO | flagIndir)
+	fl := v.flag & (flagStickyRO | flagIndir) // Clear flagEmbedRO
 	fl |= flag(Func)
 	fl |= flag(i)<<flagMethodShift | flagMethod
 	return Value{v.typ, v.ptr, fl}
-- 
2.50.0