libgo: update to Go 1.15.4 release

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/268177

2 files changed, 22 insertions, 2 deletions

diff --git a/libgo/go/reflect/deepequal.go b/libgo/go/reflect/deepequal.go
index 8a2bf8b..b99c345 100644
--- a/libgo/go/reflect/deepequal.go
+++ b/libgo/go/reflect/deepequal.go
@@ -37,7 +37,17 @@ func deepValueEqual(v1, v2 Value, visited map[visit]bool, depth int) bool {
 	// and it's safe and valid to get Value's internal pointer.
 	hard := func(v1, v2 Value) bool {
 		switch v1.Kind() {
-		case Map, Slice, Ptr, Interface:
+		case Ptr:
+			if v1.typ.ptrdata == 0 {
+				// go:notinheap pointers can't be cyclic.
+				// At least, all of our current uses of go:notinheap have
+				// that property. The runtime ones aren't cyclic (and we don't use
+				// DeepEqual on them anyway), and the cgo-generated ones are
+				// all empty structs.
+				return false
+			}
+			fallthrough
+		case Map, Slice, Interface:
 			// Nil pointers cannot be cyclic. Avoid putting them in the visited map.
 			return !v1.IsNil() && !v2.IsNil()
 		}
diff --git a/libgo/go/reflect/value.go b/libgo/go/reflect/value.go
index 64f7432..1394dd3 100644
--- a/libgo/go/reflect/value.go
+++ b/libgo/go/reflect/value.go
@@ -91,6 +91,7 @@ func (f flag) ro() flag {
 
 // pointer returns the underlying pointer represented by v.
 // v.Kind() must be Ptr, Map, Chan, Func, or UnsafePointer
+// if v.Kind() == Ptr, the base type must not be go:notinheap.
 func (v Value) pointer() unsafe.Pointer {
 	if v.typ.size != ptrSize || !v.typ.pointers() {
 		panic("can't call pointer on a non-pointer Value")
@@ -1263,7 +1264,16 @@ func (v Value) Pointer() uintptr {
 	// TODO: deprecate
 	k := v.kind()
 	switch k {
-	case Chan, Map, Ptr, UnsafePointer:
+	case Ptr:
+		if v.typ.ptrdata == 0 {
+			// Handle pointers to go:notinheap types directly,
+			// so we never materialize such pointers as an
+			// unsafe.Pointer. (Such pointers are always indirect.)
+			// See issue 42076.
+			return *(*uintptr)(v.ptr)
+		}
+		fallthrough
+	case Chan, Map, UnsafePointer:
 		return uintptr(v.pointer())
 	case Func:
 		p := v.pointer()