reflect: correct type descriptor for call of interface method
When preparing a call with an interface method, the argument
frame holds the receiver "iword", but funcLayout was being
asked to write a descriptor as if the receiver were a complete
interface value. This was originally caught by running a large
program with Debug=3 in runtime/mgc0.c, but the new panic
in funcLayout suffices to catch the mistake with the existing
tests.
Fixes #7748.
LGTM=bradfitz, iant
R=golang-codereviews, bradfitz, iant
CC=golang-codereviews, khr
https://golang.org/cl/88100048
diff --git a/src/pkg/reflect/value.go b/src/pkg/reflect/value.go
index 720090b..39cc919 100644
--- a/src/pkg/reflect/value.go
+++ b/src/pkg/reflect/value.go
@@ -440,9 +440,8 @@
rcvrtype *rtype
)
if v.flag&flagMethod != 0 {
- rcvrtype = t
rcvr = v
- t, fn = methodReceiver(op, v, int(v.flag)>>flagMethodShift)
+ rcvrtype, t, fn = methodReceiver(op, v, int(v.flag)>>flagMethodShift)
} else if v.flag&flagIndir != 0 {
fn = *(*unsafe.Pointer)(v.ptr)
} else {
@@ -529,8 +528,7 @@
y := (*methodValue)(fn)
if y.fn == methodValueCallCode {
rcvr = y.rcvr
- rcvrtype = rcvr.typ
- t, fn = methodReceiver("call", rcvr, y.method)
+ rcvrtype, t, fn = methodReceiver("call", rcvr, y.method)
}
// Compute frame type, allocate a chunk of memory for frame
@@ -668,9 +666,10 @@
// described by v. The Value v may or may not have the
// flagMethod bit set, so the kind cached in v.flag should
// not be used.
+// The return value rcvrtype gives the method's actual receiver type.
// The return value t gives the method type signature (without the receiver).
// The return value fn is a pointer to the method code.
-func methodReceiver(op string, v Value, methodIndex int) (t *rtype, fn unsafe.Pointer) {
+func methodReceiver(op string, v Value, methodIndex int) (rcvrtype, t *rtype, fn unsafe.Pointer) {
i := methodIndex
if v.typ.Kind() == Interface {
tt := (*interfaceType)(unsafe.Pointer(v.typ))
@@ -685,9 +684,11 @@
if iface.itab == nil {
panic("reflect: " + op + " of method on nil interface value")
}
+ rcvrtype = iface.itab.typ
fn = unsafe.Pointer(&iface.itab.fun[i])
t = m.typ
} else {
+ rcvrtype = v.typ
ut := v.typ.uncommon()
if ut == nil || i < 0 || i >= len(ut.methods) {
panic("reflect: internal error: invalid method index")
@@ -746,8 +747,7 @@
// The gc compilers know to do that for the name "reflect.callMethod".
func callMethod(ctxt *methodValue, frame unsafe.Pointer) {
rcvr := ctxt.rcvr
- rcvrtype := rcvr.typ
- t, fn := methodReceiver("call", rcvr, ctxt.method)
+ rcvrtype, t, fn := methodReceiver("call", rcvr, ctxt.method)
frametype, argSize, retOffset := funcLayout(t, rcvrtype)
// Make a new frame that is one word bigger so we can store the receiver.
