mobile/bind: stop tracking foreign objects in the Go reference tracker

ToRefNum only handles Go objects, but it can be passed foreign object
proxies as well. Add a check whether the object is a proxy, and if so,
simply return its refnum and don't track it.

Change-Id: Ib17bd11b48e472c3bec0e5fb06661b201c3dfa97
Reviewed-on: https://go-review.googlesource.com/20681
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

bind/gengo.go

@@ -275,6 +275,8 @@ func (g *goGen) genInterface(obj *types.TypeName) {
 	}
 	g.Printf("type proxy%s_%s _seq.Ref\n\n", g.pkgPrefix, obj.Name())
 
+	g.Printf("func (p *proxy%s_%s) Bind_proxy_refnum__() int32 { return p.Num }\n\n", g.pkgPrefix, obj.Name())
+
 	for _, m := range summary.callable {
 		sig := m.Type().(*types.Signature)
 		params := sig.Params()

bind/java/SeqTest.java

@@ -497,4 +497,9 @@ public class SeqTest extends InstrumentationTestCase {
     Testpkg.WithImportedI(i);
     Testpkg.WithImportedS(s);
   }
+
+  public void testIDup() {
+    Testpkg.I want = new AnI();
+    assertTrue("java object passed through Go should not be wrapped", want == Testpkg.IDup(want));
+  }
 }

bind/objc/SeqTest.m

@@ -367,4 +367,10 @@ static int numI = 0;
 	[fields setS:s];
 }
 
+- (void)testIDup {
+	Number *want = [[Number alloc] init];
+	Number *got = GoTestpkgIDup(want);
+	XCTAssertEqual(got, want, @"ObjC object passed through Go should not be wrapped");
+}
+
 @end

bind/seq/ref.go

@@ -45,9 +45,23 @@ type Ref struct {
 	Num int32
 }
 
-// ToRefNum increments the reference count for a Go object and
-// return its refnum.
+type proxy interface {
+	// Use a strange name and hope that user code does not implement it
+	Bind_proxy_refnum__() int32
+}
+
+// ToRefNum increments the reference count for an object and
+// returns its refnum.
 func ToRefNum(obj interface{}) int32 {
+	// We don't track foreign objects, so if obj is a proxy
+	// return its refnum.
+	if r, ok := obj.(proxy); ok {
+		refnum := r.Bind_proxy_refnum__()
+		if refnum <= 0 {
+			panic(fmt.Errorf("seq: proxy contained invalid Go refnum: %d", refnum))
+		}
+		return refnum
+	}
 	refs.Lock()
 	num := refs.refs[obj]
 	if num != 0 {

bind/testdata/interfaces.go.golden

@@ -38,6 +38,8 @@ func proxyinterfaces_Error_Err(refnum C.int32_t) C.nstring {
 
 type proxyinterfaces_Error _seq.Ref
 
+func (p *proxyinterfaces_Error) Bind_proxy_refnum__() int32 { return p.Num }
+
 func (p *proxyinterfaces_Error) Err() error {
 	res := C.cproxyinterfaces_Error_Err(C.int32_t(p.Num))
 	_res_str := decodeString(res)
@@ -56,6 +58,8 @@ func proxyinterfaces_I_Rand(refnum C.int32_t) C.int32_t {
 
 type proxyinterfaces_I _seq.Ref
 
+func (p *proxyinterfaces_I) Bind_proxy_refnum__() int32 { return p.Num }
+
 func (p *proxyinterfaces_I) Rand() int32 {
 	res := C.cproxyinterfaces_I_Rand(C.int32_t(p.Num))
 	_res := int32(res)
@@ -90,6 +94,8 @@ func proxyinterfaces_I3_F(refnum C.int32_t) C.int32_t {
 
 type proxyinterfaces_I3 _seq.Ref
 
+func (p *proxyinterfaces_I3) Bind_proxy_refnum__() int32 { return p.Num }
+
 func (p *proxyinterfaces_I3) F() interfaces.I1 {
 	res := C.cproxyinterfaces_I3_F(C.int32_t(p.Num))
 	var _res interfaces.I1
@@ -112,6 +118,8 @@ func proxyinterfaces_WithParam_HasParam(refnum C.int32_t, param_p0 C.char) {
 
 type proxyinterfaces_WithParam _seq.Ref
 
+func (p *proxyinterfaces_WithParam) Bind_proxy_refnum__() int32 { return p.Num }
+
 func (p *proxyinterfaces_WithParam) HasParam(param_p0 bool) {
 	var _param_p0 C.char = 0
 	if param_p0 {

bind/testdata/issue10788.go.golden

@@ -58,6 +58,8 @@ func proxyissue10788_TestInterface_MultipleUnnamedParams(refnum C.int32_t, param
 
 type proxyissue10788_TestInterface _seq.Ref
 
+func (p *proxyissue10788_TestInterface) Bind_proxy_refnum__() int32 { return p.Num }
+
 func (p *proxyissue10788_TestInterface) DoSomeWork(param_s *issue10788.TestStruct) {
 	var _param_s C.int32_t = _seq.NullRefNum
 	if param_s != nil {

bind/testdata/issue12403.go.golden

@@ -49,6 +49,8 @@ func proxyissue12403_Parsable_ToJSON(refnum C.int32_t) (C.nstring, C.nstring) {
 
 type proxyissue12403_Parsable _seq.Ref
 
+func (p *proxyissue12403_Parsable) Bind_proxy_refnum__() int32 { return p.Num }
+
 func (p *proxyissue12403_Parsable) FromJSON(param_jstr string) string {
 	_param_jstr := encodeString(param_jstr)
 	res := C.cproxyissue12403_Parsable_FromJSON(C.int32_t(p.Num), _param_jstr)

bind/testdata/structs.go.golden

@@ -104,6 +104,8 @@ func proxystructs_I_M(refnum C.int32_t) {
 
 type proxystructs_I _seq.Ref
 
+func (p *proxystructs_I) Bind_proxy_refnum__() int32 { return p.Num }
+
 func (p *proxystructs_I) M() {
 	C.cproxystructs_I_M(C.int32_t(p.Num))
 }

bind/testdata/vars.go.golden

@@ -23,6 +23,8 @@ var _ = _seq.FromRefNum
 
 type proxyvars_I _seq.Ref
 
+func (p *proxyvars_I) Bind_proxy_refnum__() int32 { return p.Num }
+
 //export var_setvars_ABool
 func var_setvars_ABool(v C.char) {
 	_v := v != 0

bind/testpkg/testpkg.go

@@ -138,6 +138,10 @@ func NumSCollected() int {
 	return numSCollected
 }
 
+func IDup(i I) I {
+	return i
+}
+
 func StrDup(s string) string {
 	return s
 }