Bug 541003 - CPOW: Support throwing arbitrary exceptions from content to chrome. r=mrbkap

* * *
CPOW-specific exceptions (bug 541003). r=mrbkap

js/src/ipc/ObjectWrapperChild.cpp

@@ -59,6 +59,8 @@ namespace {
 
         nsCxPusher mStack;
         JSAutoRequest mRequest;
+        JSContext* const mContext;
+        const uint32 mSavedOptions;
         JS_DECL_USE_GUARD_OBJECT_NOTIFIER;
 
     public:
@@ -66,6 +68,9 @@ namespace {
         AutoContextPusher(JSContext* cx
                           JS_GUARD_OBJECT_NOTIFIER_PARAM)
             : mRequest(cx)
+            , mContext(cx)
+            , mSavedOptions(JS_SetOptions(cx, (JS_GetOptions(cx) |
+                                               JSOPTION_DONT_REPORT_UNCAUGHT)))
         {
             JS_GUARD_OBJECT_NOTIFIER_INIT;
             mStack.Push(cx);
@@ -73,10 +78,70 @@ namespace {
 
         ~AutoContextPusher() {
             mStack.Pop();
+            JS_SetOptions(mContext, mSavedOptions);
         }
 
     };
 
+    class StatusPtrOwner
+    {
+        OperationStatus* mStatusPtr;
+    public:
+        StatusPtrOwner() : mStatusPtr(NULL) {}
+        void SetStatusPtr(OperationStatus* statusPtr) {
+            mStatusPtr = statusPtr;
+            // By default, initialize mStatusPtr to failure without an
+            // exception.  Doing so only when the union is uninitialized
+            // allows AutoCheckOperation classes to be nested on the
+            // stack, just in case AnswerConstruct, for example, calls
+            // AnswerCall (as it once did, before there were unrelated
+            // problems with that approach).
+            if (mStatusPtr->type() == OperationStatus::T__None)
+                *mStatusPtr = JS_FALSE;
+        }
+        OperationStatus* StatusPtr() {
+            NS_ASSERTION(mStatusPtr, "Should have called SetStatusPtr by now.");
+            return mStatusPtr;
+        }
+    };
+
+    typedef AutoCheckOperationBase<StatusPtrOwner> ACOBase;
+
+    class AutoCheckOperation : public ACOBase
+    {
+        JS_DECL_USE_GUARD_OBJECT_NOTIFIER;
+    public:
+        AutoCheckOperation(ObjectWrapperChild* owc,
+                           OperationStatus* statusPtr
+                           JS_GUARD_OBJECT_NOTIFIER_PARAM)
+            : ACOBase(NULL, owc)
+        {
+            JS_GUARD_OBJECT_NOTIFIER_INIT;
+            SetStatusPtr(statusPtr);
+        }
+    };
+}
+
+void
+ObjectWrapperChild::CheckOperation(JSContext*,
+                                   OperationStatus* status)
+{
+    NS_PRECONDITION(status->type() != OperationStatus::T__None,
+                    "Checking an uninitialized operation.");
+
+    JSContext* cx = Manager()->GetContext();
+    jsval thrown;
+
+    if (JS_GetPendingException(cx, &thrown)) {
+        NS_ASSERTION(!(status->type() == OperationStatus::TJSBool &&
+                       status->get_JSBool()),
+                     "Operation succeeded but exception was thrown?");
+        JSVariant exception;
+        if (!jsval_to_JSVariant(cx, thrown, &exception))
+            exception = void_t(); // XXX Useful?
+        *status = exception;
+        JS_ClearPendingException(cx);
+    }
 }
 
 ObjectWrapperChild::ObjectWrapperChild(JSContext* cx, JSObject* obj)
@@ -257,88 +322,85 @@ ObjectWrapperChild::AnswerSomething(/* in-parameters */
 
 bool
 ObjectWrapperChild::AnswerAddProperty(const nsString& id,
-                                      JSBool* ok)
+                                      OperationStatus* status)
 {
     jsid interned_id;
 
-    *ok = JS_FALSE;
-
     JSContext* cx = Manager()->GetContext();
     AutoContextPusher acp(cx);
+    AutoCheckOperation aco(this, status);
 
     if (!jsid_from_nsString(cx, id, &interned_id))
         return false;
     
-    *ok = JS_DefinePropertyById(cx, mObj, interned_id, JSVAL_VOID,
+    *status = JS_DefinePropertyById(cx, mObj, interned_id, JSVAL_VOID,
                                     NULL, NULL, 0);
     return true;
 }
 
 bool
 ObjectWrapperChild::AnswerGetProperty(const nsString& id,
-                                      JSBool* ok, JSVariant* vp)
+                                      OperationStatus* status, JSVariant* vp)
 {
     jsid interned_id;
     jsval val;
 
-    *ok = JS_FALSE;
-
     JSContext* cx = Manager()->GetContext();
     AutoContextPusher acp(cx);
+    AutoCheckOperation aco(this, status);
 
     if (!jsid_from_nsString(cx, id, &interned_id))
         return false;
 
-    *ok = JS_GetPropertyById(cx, mObj, interned_id, &val);
+    *status = JS_GetPropertyById(cx, mObj, interned_id, &val);
 
     // Since we fully expect this call to jsval_to_JSVariant to return
     // true, we can't just leave vp uninitialized when JS_GetPropertyById
     // returns JS_FALSE.  This pitfall could be avoided in general if IPDL
     // ensured that outparams were pre-initialized to some default value
     // (XXXfixme cjones?).
-    return jsval_to_JSVariant(cx, *ok ? val : JSVAL_VOID, vp);
+    return jsval_to_JSVariant(cx, aco.Ok() ? val : JSVAL_VOID, vp);
 }
 
 bool
 ObjectWrapperChild::AnswerSetProperty(const nsString& id, const JSVariant& v,
-                                      JSBool* ok, JSVariant* vp)
+                                      OperationStatus* status, JSVariant* vp)
 {
     jsid interned_id;
     jsval val;
 
-    *ok = JS_FALSE;
     *vp = v;
 
     JSContext* cx = Manager()->GetContext();
     AutoContextPusher acp(cx);
+    AutoCheckOperation aco(this, status);
 
     if (!jsid_from_nsString(cx, id, &interned_id) ||
         !jsval_from_JSVariant(cx, v, &val))
         return false;
 
-    *ok = JS_SetPropertyById(cx, mObj, interned_id, &val);
+    *status = JS_SetPropertyById(cx, mObj, interned_id, &val);
 
-    return jsval_to_JSVariant(cx, *ok ? val : JSVAL_VOID, vp);
+    return jsval_to_JSVariant(cx, aco.Ok() ? val : JSVAL_VOID, vp);
 }
 
 bool
 ObjectWrapperChild::AnswerDelProperty(const nsString& id,
-                                      JSBool* ok, JSVariant* vp)
+                                      OperationStatus* status, JSVariant* vp)
 {
     jsid interned_id;
     jsval val;
 
-    *ok = JS_FALSE;
-
     JSContext* cx = Manager()->GetContext();
     AutoContextPusher acp(cx);
+    AutoCheckOperation aco(this, status);
 
     if (!jsid_from_nsString(cx, id, &interned_id))
         return false;
 
-    *ok = JS_DeletePropertyById2(cx, mObj, interned_id, &val);
+    *status = JS_DeletePropertyById2(cx, mObj, interned_id, &val);
 
-    return jsval_to_JSVariant(cx, *ok ? val : JSVAL_VOID, vp);
+    return jsval_to_JSVariant(cx, aco.Ok() ? val : JSVAL_VOID, vp);
 }
 
 static const PRUint32 sNextIdIndexSlot = 0;
@@ -370,13 +432,13 @@ static const JSClass sCPOW_NewEnumerateState_JSClass = {
 
 bool
 ObjectWrapperChild::AnswerNewEnumerateInit(/* no in-parameters */
-                                           JSBool* ok, JSVariant* statep, int* idp)
+                                           OperationStatus* status, JSVariant* statep, int* idp)
 {
-    *ok = JS_FALSE;
     *idp = 0;
 
     JSContext* cx = Manager()->GetContext();
     AutoContextPusher acp(cx);
+    AutoCheckOperation aco(this, status);
 
     JSClass* clasp = const_cast<JSClass*>(&sCPOW_NewEnumerateState_JSClass);
     JSObject* state = JS_NewObjectWithGivenProto(cx, clasp, NULL, NULL);
@@ -408,7 +470,7 @@ ObjectWrapperChild::AnswerNewEnumerateInit(/* no in-parameters */
     }
     *idp = strIds->Length();
 
-    *ok = (JS_SetPrivate(cx, state, strIds) &&
+    *status = (JS_SetPrivate(cx, state, strIds) &&
                JS_SetReservedSlot(cx, state, sNextIdIndexSlot,
                                   JSVAL_ZERO) &&
                JSObject_to_JSVariant(cx, state, statep));
@@ -418,17 +480,17 @@ ObjectWrapperChild::AnswerNewEnumerateInit(/* no in-parameters */
 
 bool
 ObjectWrapperChild::AnswerNewEnumerateNext(const JSVariant& in_state,
-                                           JSBool* ok, JSVariant* statep, nsString* idp)
+                                           OperationStatus* status, JSVariant* statep, nsString* idp)
 {
     JSObject* state;
     jsval v;
 
-    *ok = JS_FALSE;
     *statep = in_state;
     idp->Truncate();
     
     JSContext* cx = Manager()->GetContext();
     AutoContextPusher acp(cx);
+    AutoCheckOperation aco(this, status);
 
     if (!JSObject_from_JSVariant(cx, in_state, &state))
         return false;
@@ -444,12 +506,12 @@ ObjectWrapperChild::AnswerNewEnumerateNext(const JSVariant& in_state,
     NS_ASSERTION(i <= strIds->Length(), "Index of next jsid too large?");
 
     if (i == strIds->Length()) {
-        *ok = JS_TRUE;
+        *status = JS_TRUE;
         return JSObject_to_JSVariant(cx, NULL, statep);
     }
 
     *idp = strIds->ElementAt(i);
-    *ok = JS_SetReservedSlot(cx, state, sNextIdIndexSlot,
+    *status = JS_SetReservedSlot(cx, state, sNextIdIndexSlot,
                                  INT_TO_JSVAL(i + 1));
     return true;
 }
@@ -472,15 +534,15 @@ ObjectWrapperChild::RecvNewEnumerateDestroy(const JSVariant& in_state)
 
 bool
 ObjectWrapperChild::AnswerNewResolve(const nsString& id, const int& flags,
-                                     JSBool* ok, PObjectWrapperChild** obj2)
+                                     OperationStatus* status, PObjectWrapperChild** obj2)
 {
     jsid interned_id;
     
-    *ok = JS_FALSE;
     *obj2 = NULL;
 
     JSContext* cx = Manager()->GetContext();
     AutoContextPusher acp(cx);
+    AutoCheckOperation aco(this, status);
 
     if (!jsid_from_nsString(cx, id, &interned_id))
         return false;
@@ -492,7 +554,7 @@ ObjectWrapperChild::AnswerNewResolve(const nsString& id, const int& flags,
     if (!JS_GetPropertyDescriptorById(cx, mObj, interned_id, flags, &desc))
         return true;
 
-    *ok = JS_TRUE;
+    *status = JS_TRUE;
 
     if (desc.obj)
         *obj2 = Manager()->GetOrCreateWrapper(desc.obj);
@@ -502,13 +564,14 @@ ObjectWrapperChild::AnswerNewResolve(const nsString& id, const int& flags,
 
 bool
 ObjectWrapperChild::AnswerConvert(const JSType& type,
-                                  JSBool* ok, JSVariant* vp)
+                                  OperationStatus* status, JSVariant* vp)
 {
     jsval v;
     JSContext* cx = Manager()->GetContext();
     AutoContextPusher acp(cx);
-    *ok = JS_ConvertValue(cx, OBJECT_TO_JSVAL(mObj), type, &v);
-    return jsval_to_JSVariant(cx, *ok ? v : JSVAL_VOID, vp);
+    AutoCheckOperation aco(this, status);
+    *status = JS_ConvertValue(cx, OBJECT_TO_JSVAL(mObj), type, &v);
+    return jsval_to_JSVariant(cx, aco.Ok() ? v : JSVAL_VOID, vp);
 }
 
 namespace {
@@ -518,12 +581,11 @@ namespace {
 
 bool
 ObjectWrapperChild::AnswerCall(PObjectWrapperChild* receiver, const nsTArray<JSVariant>& argv,
-                               JSBool* ok, JSVariant* rval)
+                               OperationStatus* status, JSVariant* rval)
 {
-    *ok = JS_FALSE;
-
     JSContext* cx = Manager()->GetContext();
     AutoContextPusher acp(cx);
+    AutoCheckOperation aco(this, status);
 
     JSObject* obj;
     if (!JSObject_from_PObjectWrapperChild(cx, receiver, &obj))
@@ -541,20 +603,19 @@ ObjectWrapperChild::AnswerCall(PObjectWrapperChild* receiver, const nsTArray<JSV
             return false;
 
     jsval rv;
-    *ok = JS_CallFunctionValue(cx, obj, OBJECT_TO_JSVAL(mObj),
+    *status = JS_CallFunctionValue(cx, obj, OBJECT_TO_JSVAL(mObj),
                                    argv.Length(), jsargs, &rv);
 
-    return jsval_to_JSVariant(cx, *ok ? rv : JSVAL_VOID, rval);
+    return jsval_to_JSVariant(cx, aco.Ok() ? rv : JSVAL_VOID, rval);
 }
 
 bool
 ObjectWrapperChild::AnswerConstruct(const nsTArray<JSVariant>& argv,
-                                    JSBool* ok, PObjectWrapperChild** rval)
+                                    OperationStatus* status, PObjectWrapperChild** rval)
 {
-    *ok = JS_FALSE;
-
     JSContext* cx = Manager()->GetContext();
     AutoContextPusher acp(cx);
+    AutoCheckOperation aco(this, status);
 
     AutoJSArgs args;
     PRUint32 argc = argv.Length();
@@ -569,7 +630,7 @@ ObjectWrapperChild::AnswerConstruct(const nsTArray<JSVariant>& argv,
 
     JSObject* obj = JS_New(cx, mObj, argc, jsargs);
 
-    *ok = !!obj;
+    *status = !!obj;
     *rval = Manager()->GetOrCreateWrapper(obj);
 
     return true;
@@ -577,13 +638,14 @@ ObjectWrapperChild::AnswerConstruct(const nsTArray<JSVariant>& argv,
 
 bool
 ObjectWrapperChild::AnswerHasInstance(const JSVariant& v,
-                                      JSBool* ok, JSBool* bp)
+                                      OperationStatus* status, JSBool* bp)
 {
     jsval candidate;
     JSContext* cx = Manager()->GetContext();
     AutoContextPusher acp(cx);
+    AutoCheckOperation aco(this, status);
     if (!jsval_from_JSVariant(cx, v, &candidate))
         return false;
-    *ok = JS_HasInstance(cx, mObj, candidate, bp);
+    *status = JS_HasInstance(cx, mObj, candidate, bp);
     return true;
 }

js/src/ipc/ObjectWrapperChild.h

@@ -43,6 +43,9 @@
 
 #include "mozilla/jsipc/PObjectWrapperChild.h"
 
+// For OperationChecker and AutoCheckOperationBase.
+#include "mozilla/jsipc/ObjectWrapperParent.h"
+
 using mozilla::jsipc::JSVariant;
 
 namespace mozilla {
@@ -52,6 +55,7 @@ class ContextWrapperChild;
 
 class ObjectWrapperChild
     : public PObjectWrapperChild
+    , public OperationChecker
 {
 public:
 
@@ -59,6 +63,8 @@ public:
 
     JSObject* GetJSObject() const { return mObj; }
 
+    void CheckOperation(JSContext* cx, OperationStatus* status);
+    
 private:
 
     JSObject* const mObj;
@@ -81,39 +87,39 @@ protected:
     void ActorDestroy(ActorDestroyReason why);
 
     bool AnswerAddProperty(const nsString& id,
-                           JSBool* ok);
+                           OperationStatus* status);
 
     bool AnswerGetProperty(const nsString& id,
-                           JSBool* ok, JSVariant* vp);
+                           OperationStatus* status, JSVariant* vp);
 
     bool AnswerSetProperty(const nsString& id, const JSVariant& v,
-                           JSBool* ok, JSVariant* vp);
+                           OperationStatus* status, JSVariant* vp);
 
     bool AnswerDelProperty(const nsString& id,
-                           JSBool* ok, JSVariant* vp);
+                           OperationStatus* status, JSVariant* vp);
 
     bool AnswerNewEnumerateInit(/* no in-parameters */
-                                JSBool* ok, JSVariant* statep, int* idp);
+                                OperationStatus* status, JSVariant* statep, int* idp);
 
     bool AnswerNewEnumerateNext(const JSVariant& in_state,
-                                JSBool* ok, JSVariant* statep, nsString* idp);
+                                OperationStatus* status, JSVariant* statep, nsString* idp);
 
     bool RecvNewEnumerateDestroy(const JSVariant& in_state);
 
     bool AnswerNewResolve(const nsString& id, const int& flags,
-                          JSBool* ok, PObjectWrapperChild** obj2);
+                          OperationStatus* status, PObjectWrapperChild** obj2);
 
     bool AnswerConvert(const JSType& type,
-                       JSBool* ok, JSVariant* vp);
+                       OperationStatus* status, JSVariant* vp);
 
     bool AnswerCall(PObjectWrapperChild* receiver, const nsTArray<JSVariant>& argv,
-                    JSBool* ok, JSVariant* rval);
+                    OperationStatus* status, JSVariant* rval);
 
     bool AnswerConstruct(const nsTArray<JSVariant>& argv,
-                         JSBool* ok, PObjectWrapperChild** rval);
+                         OperationStatus* status, PObjectWrapperChild** rval);
 
     bool AnswerHasInstance(const JSVariant& v,
-                           JSBool* ok, JSBool* bp);
+                           OperationStatus* status, JSBool* bp);
 };
 
 }}

js/src/ipc/ObjectWrapperParent.cpp

@@ -103,6 +103,69 @@ namespace {
 
     };
 
+    class StatusMemberOwner
+    {
+        OperationStatus mStatus;
+    public:
+        StatusMemberOwner() : mStatus(JS_FALSE) {}
+        OperationStatus* StatusPtr() {
+            return &mStatus;
+        }
+    };
+
+    typedef AutoCheckOperationBase<StatusMemberOwner> ACOBase;
+
+    class AutoCheckOperation : public ACOBase
+    {
+        JS_DECL_USE_GUARD_OBJECT_NOTIFIER;
+    public:
+        AutoCheckOperation(JSContext* cx,
+                           ObjectWrapperParent* owp
+                           JS_GUARD_OBJECT_NOTIFIER_PARAM)
+            : ACOBase(cx, owp)
+        {
+            JS_GUARD_OBJECT_NOTIFIER_INIT;
+        }
+    };
+
+}
+
+void
+ObjectWrapperParent::CheckOperation(JSContext* cx,
+                                    OperationStatus* status)
+{
+    NS_PRECONDITION(status->type() != OperationStatus::T__None,
+                    "Checking an uninitialized operation.");
+
+    switch (status->type()) {
+    case OperationStatus::TJSVariant:
+        {
+            jsval thrown;
+            if (jsval_from_JSVariant(cx, status->get_JSVariant(), &thrown))
+                JS_SetPendingException(cx, thrown);
+            *status = JS_FALSE;
+        }
+        break;
+    case OperationStatus::TJSBool:
+        if (!status->get_JSBool() && !JS_IsExceptionPending(cx)) {
+            NS_WARNING("CPOW operation failed without setting an exception.");
+        }
+        break;
+    default:
+        NS_NOTREACHED("Invalid or uninitialized OperationStatus type.");
+        break;
+    }
+}
+
+template <typename RType>
+static RType
+with_error(JSContext* cx,
+               RType rval,
+               const char* error = NULL)
+{
+    if (!JS_IsExceptionPending(cx))
+        JS_ReportError(cx, error ? error : "Unspecified CPOW error");
+    return rval;
 }
 
 const JSExtendedClass ObjectWrapperParent::sCPOW_JSClass = {
@@ -198,7 +261,7 @@ ObjectWrapperParent::jsval_to_JSVariant(JSContext* cx, jsval from,
         {
             PObjectWrapperParent* powp;
             if (!JSObject_to_PObjectWrapperParent(cx, JSVAL_TO_OBJECT(from), &powp))
-                return false;
+                return with_error(cx, false, "Cannot pass parent-created object to child");
             *to = powp;
         }
         return true;
@@ -217,8 +280,9 @@ ObjectWrapperParent::jsval_to_JSVariant(JSContext* cx, jsval from,
         *to = !!JSVAL_TO_BOOLEAN(from);
         return true;
     case JSTYPE_XML:
+        return with_error(cx, false, "CPOWs currently cannot handle JSTYPE_XML");
     default:
-        return false;
+        return with_error(cx, false, "Bad jsval type");
     }
 }
 
@@ -332,22 +396,22 @@ ObjectWrapperParent::CPOW_AddProperty(JSContext *cx, JSObject *obj, jsval id,
 
     ObjectWrapperParent* self = Unwrap(cx, obj);
     if (!self)
-        return JS_FALSE;
+        return with_error(cx, JS_FALSE, "Unwrapping failed in CPOW_AddProperty");
 
     if (AutoResolveFlag::IsSet(cx, obj))
         return JS_TRUE;
 
+    AutoCheckOperation aco(cx, self);
+
     nsString in_id;
 
     if (!jsval_to_nsString(cx, id, &in_id))
         return JS_FALSE;
 
-    JSBool out_ok;
-
     return (self->Manager()->RequestRunToCompletion() &&
             self->CallAddProperty(in_id,
-                                  &out_ok) &&
-            out_ok);
+                                  aco.StatusPtr()) &&
+            aco.Ok());
 }
 
 /*static*/ JSBool
@@ -359,20 +423,21 @@ ObjectWrapperParent::CPOW_GetProperty(JSContext *cx, JSObject *obj, jsval id,
 
     ObjectWrapperParent* self = Unwrap(cx, obj);
     if (!self)
-        return JS_FALSE;
+        return with_error(cx, JS_FALSE, "Unwrapping failed in CPOW_GetProperty");
+
+    AutoCheckOperation aco(cx, self);
 
     nsString in_id;
 
     if (!jsval_to_nsString(cx, id, &in_id))
         return JS_FALSE;
 
-    JSBool out_ok;
     JSVariant out_v;
     
     return (self->Manager()->RequestRunToCompletion() &&
             self->CallGetProperty(in_id,
-                                  &out_ok, &out_v) &&
-            out_ok &&
+                                  aco.StatusPtr(), &out_v) &&
+            aco.Ok() &&
             self->jsval_from_JSVariant(cx, out_v, vp));
 }
 
@@ -385,7 +450,9 @@ ObjectWrapperParent::CPOW_SetProperty(JSContext *cx, JSObject *obj, jsval id,
 
     ObjectWrapperParent* self = Unwrap(cx, obj);
     if (!self)
-        return JS_FALSE;
+        return with_error(cx, JS_FALSE, "Unwrapping failed in CPOW_SetProperty");
+
+    AutoCheckOperation aco(cx, self);
 
     nsString in_id;
     JSVariant in_v;
@@ -394,13 +461,12 @@ ObjectWrapperParent::CPOW_SetProperty(JSContext *cx, JSObject *obj, jsval id,
         !self->jsval_to_JSVariant(cx, *vp, &in_v))
         return JS_FALSE;
 
-    JSBool out_ok;
     JSVariant out_v;
 
     return (self->Manager()->RequestRunToCompletion() &&
             self->CallSetProperty(in_id, in_v,
-                                  &out_ok, &out_v) &&
-            out_ok &&
+                                  aco.StatusPtr(), &out_v) &&
+            aco.Ok() &&
             self->jsval_from_JSVariant(cx, out_v, vp));
 }    
     
@@ -413,32 +479,34 @@ ObjectWrapperParent::CPOW_DelProperty(JSContext *cx, JSObject *obj, jsval id,
 
     ObjectWrapperParent* self = Unwrap(cx, obj);
     if (!self)
-        return JS_FALSE;
+        return with_error(cx, JS_FALSE, "Unwrapping failed in CPOW_DelProperty");
+
+    AutoCheckOperation aco(cx, self);
 
     nsString in_id;
 
     if (!jsval_to_nsString(cx, id, &in_id))
         return JS_FALSE;
 
-    JSBool out_ok;
     JSVariant out_v;
     
     return (self->Manager()->RequestRunToCompletion() &&
             self->CallDelProperty(in_id,
-                                  &out_ok, &out_v) &&
-            out_ok &&
+                                  aco.StatusPtr(), &out_v) &&
+            aco.Ok() &&
             jsval_from_JSVariant(cx, out_v, vp));
 }
 
 JSBool
 ObjectWrapperParent::NewEnumerateInit(JSContext* cx, jsval* statep, jsid* idp)
 {
-    JSBool out_ok;
+    AutoCheckOperation aco(cx, this);
+
     JSVariant out_state;
     int out_id;
 
-    return (CallNewEnumerateInit(&out_ok, &out_state, &out_id) &&
-            out_ok &&
+    return (CallNewEnumerateInit(aco.StatusPtr(), &out_state, &out_id) &&
+            aco.Ok() &&
             jsval_from_JSVariant(cx, out_state, statep) &&
             (!idp || jsid_from_int(cx, out_id, idp)));
 }
@@ -446,17 +514,19 @@ ObjectWrapperParent::NewEnumerateInit(JSContext* cx, jsval* statep, jsid* idp)
 JSBool
 ObjectWrapperParent::NewEnumerateNext(JSContext* cx, jsval* statep, jsid* idp)
 {
+    AutoCheckOperation aco(cx, this);
+
     JSVariant in_state;
+
     if (!jsval_to_JSVariant(cx, *statep, &in_state))
         return JS_FALSE;
 
-    JSBool out_ok;
     JSVariant out_state;
     nsString out_id;
 
     if (CallNewEnumerateNext(in_state,
-                             &out_ok, &out_state, &out_id) &&
-        out_ok &&
+                             aco.StatusPtr(), &out_state, &out_id) &&
+        aco.Ok() &&
         jsval_from_JSVariant(cx, out_state, statep) &&
         jsid_from_nsString(cx, out_id, idp))
     {
@@ -471,7 +541,10 @@ ObjectWrapperParent::NewEnumerateNext(JSContext* cx, jsval* statep, jsid* idp)
 JSBool
 ObjectWrapperParent::NewEnumerateDestroy(JSContext* cx, jsval state)
 {
+    AutoCheckOperation aco(cx, this);
+
     JSVariant in_state;
+
     if (!jsval_to_JSVariant(cx, state, &in_state))
         return JS_FALSE;
 
@@ -487,7 +560,7 @@ ObjectWrapperParent::CPOW_NewEnumerate(JSContext *cx, JSObject *obj,
 
     ObjectWrapperParent* self = Unwrap(cx, obj);
     if (!self)
-        return JS_FALSE;
+        return with_error(cx, JS_FALSE, "Unwrapping failed in CPOW_NewEnumerate");
 
     switch (enum_op) {
     case JSENUMERATE_INIT:
@@ -499,6 +572,7 @@ ObjectWrapperParent::CPOW_NewEnumerate(JSContext *cx, JSObject *obj,
         return self->NewEnumerateDestroy(cx, *statep);
     }
 
+    NS_NOTREACHED("Unknown enum_op value in CPOW_NewEnumerate");
     return JS_FALSE;
 }
 
@@ -511,20 +585,21 @@ ObjectWrapperParent::CPOW_NewResolve(JSContext *cx, JSObject *obj, jsval id,
 
     ObjectWrapperParent* self = Unwrap(cx, obj);
     if (!self)
-        return JS_FALSE;
+        return with_error(cx, JS_FALSE, "Unwrapping failed in CPOW_NewResolve");
+
+    AutoCheckOperation aco(cx, self);
 
     nsString in_id;
 
     if (!jsval_to_nsString(cx, id, &in_id))
         return JS_FALSE;
 
-    JSBool out_ok;
     PObjectWrapperParent* out_pobj;
 
     if (!self->Manager()->RequestRunToCompletion() ||
         !self->CallNewResolve(in_id, flags,
-                              &out_ok, &out_pobj) ||
-        !out_ok ||
+                              aco.StatusPtr(), &out_pobj) ||
+        !aco.Ok() ||
         !JSObject_from_PObjectWrapperParent(cx, out_pobj, objp))
         return JS_FALSE;
 
@@ -547,7 +622,7 @@ ObjectWrapperParent::CPOW_Convert(JSContext *cx, JSObject *obj, JSType type,
 
     ObjectWrapperParent* self = Unwrap(cx, obj);
     if (!self)
-        return JS_FALSE;
+        return with_error(cx, JS_FALSE, "Unwrapping failed in CPOW_Convert");
 
     *vp = OBJECT_TO_JSVAL(obj);
 
@@ -573,7 +648,9 @@ ObjectWrapperParent::CPOW_Call(JSContext* cx, JSObject* obj, uintN argc,
     ObjectWrapperParent* function =
         Unwrap(cx, JSVAL_TO_OBJECT(JS_ARGV_CALLEE(argv)));
     if (!function)
-        return JS_FALSE;
+        return with_error(cx, JS_FALSE, "Could not unwrap CPOW function");
+
+    AutoCheckOperation aco(cx, function);
 
     ObjectWrapperParent* receiver = Unwrap(cx, obj);
     if (!receiver) {
@@ -589,13 +666,12 @@ ObjectWrapperParent::CPOW_Call(JSContext* cx, JSObject* obj, uintN argc,
         if (!jsval_to_JSVariant(cx, argv[i], in_argv.AppendElement()))
             return JS_FALSE;
 
-    JSBool out_ok;
     JSVariant out_rval;
 
     return (function->Manager()->RequestRunToCompletion() &&
             function->CallCall(receiver, in_argv,
-                               &out_ok, &out_rval) &&
-            out_ok &&
+                               aco.StatusPtr(), &out_rval) &&
+            aco.Ok() &&
             jsval_from_JSVariant(cx, out_rval, rval));
 }
 
@@ -608,20 +684,21 @@ ObjectWrapperParent::CPOW_Construct(JSContext *cx, JSObject *obj, uintN argc,
     ObjectWrapperParent* constructor =
         Unwrap(cx, JSVAL_TO_OBJECT(JS_ARGV_CALLEE(argv)));
     if (!constructor)
-        return JS_FALSE;
+        return with_error(cx, JS_FALSE, "Could not unwrap CPOW constructor function");
+
+    AutoCheckOperation aco(cx, constructor);
 
     nsTArray<JSVariant> in_argv(argc);
     for (uintN i = 0; i < argc; i++)
         if (!jsval_to_JSVariant(cx, argv[i], in_argv.AppendElement()))
             return JS_FALSE;
 
-    JSBool out_ok;
     PObjectWrapperParent* out_powp;
 
     return (constructor->Manager()->RequestRunToCompletion() &&
             constructor->CallConstruct(in_argv,
-                                       &out_ok, &out_powp) &&
-            out_ok &&
+                                       aco.StatusPtr(), &out_powp) &&
+            aco.Ok() &&
             jsval_from_PObjectWrapperParent(cx, out_powp, rval));
 }
 
@@ -635,19 +712,19 @@ ObjectWrapperParent::CPOW_HasInstance(JSContext *cx, JSObject *obj, jsval v,
 
     ObjectWrapperParent* self = Unwrap(cx, obj);
     if (!self)
-        return JS_FALSE;
+        return with_error(cx, JS_FALSE, "Unwrapping failed in CPOW_HasInstance");
+
+    AutoCheckOperation aco(cx, self);
 
     JSVariant in_v;
 
     if (!jsval_to_JSVariant(cx, v, &in_v))
         return JS_FALSE;
 
-    JSBool out_ok;
-
     return (self->Manager()->RequestRunToCompletion() &&
             self->CallHasInstance(in_v,
-                                  &out_ok, bp) &&
-            out_ok);
+                                  aco.StatusPtr(), bp) &&
+            aco.Ok());
 }
 
 /*static*/ JSBool
@@ -660,7 +737,7 @@ ObjectWrapperParent::CPOW_Equality(JSContext *cx, JSObject *obj, jsval v,
     
     ObjectWrapperParent* self = Unwrap(cx, obj);
     if (!self)
-        return JS_FALSE;
+        return with_error(cx, JS_FALSE, "Unwrapping failed in CPOW_Equality");
 
     if (JSVAL_IS_PRIMITIVE(v))
         return JS_TRUE;

js/src/ipc/ObjectWrapperParent.h

@@ -50,8 +50,15 @@ namespace jsipc {
 
 class ContextWrapperParent;
 
+class OperationChecker {
+public:
+    virtual void CheckOperation(JSContext* cx,
+                                OperationStatus* status) = 0;
+};
+
 class ObjectWrapperParent
     : public PObjectWrapperParent
+    , public OperationChecker
 {
 public:
 
@@ -65,6 +72,9 @@ public:
         return OBJECT_TO_JSVAL(GetJSObject(cx));
     }
 
+    void CheckOperation(JSContext* cx,
+                        OperationStatus* status);
+
     static const JSExtendedClass sCPOW_JSClass;
 
 protected:
@@ -136,6 +146,33 @@ private:
                                     jsval* to);
 };
 
+template <class StatusOwnerPolicy>
+class AutoCheckOperationBase
+    : public StatusOwnerPolicy
+{
+    JSContext* const mContext;
+    OperationChecker* const mChecker;
+
+protected:
+
+    AutoCheckOperationBase(JSContext* cx,
+                           OperationChecker* checker)
+        : mContext(cx)
+        , mChecker(checker)
+    {}
+
+    virtual ~AutoCheckOperationBase() {
+        mChecker->CheckOperation(mContext, StatusOwnerPolicy::StatusPtr());
+    }
+
+public:
+
+    bool Ok() {
+        return (StatusOwnerPolicy::StatusPtr()->type() == OperationStatus::TJSBool &&
+                StatusOwnerPolicy::StatusPtr()->get_JSBool());
+    }
+};
+
 }}
 
 #endif

js/src/ipc/PObjectWrapper.ipdl

@@ -59,6 +59,11 @@ union JSVariant {
           // and IPC::ParamTraits mistakes JSIntn for int.
 };
 
+union OperationStatus {
+    JSBool;
+    JSVariant; // Exception thrown.
+};
+
 rpc protocol PObjectWrapper
 {
     manager PContextWrapper;
@@ -67,28 +72,28 @@ child:
     __delete__(); // unroot
 
     rpc AddProperty(nsString id)
-        returns (JSBool ok);
+        returns (OperationStatus status);
 
     rpc GetProperty(nsString id)
-        returns (JSBool ok,
+        returns (OperationStatus status,
                  JSVariant vp);
 
     rpc SetProperty(nsString id,
                     JSVariant v)
-        returns (JSBool ok,
+        returns (OperationStatus status,
                  JSVariant vp);
 
     rpc DelProperty(nsString id)
-        returns (JSBool ok,
+        returns (OperationStatus status,
                  JSVariant vp);
 
     rpc NewEnumerateInit()
-        returns (JSBool ok,
+        returns (OperationStatus status,
                  JSVariant statep,
                  int idp);
 
     rpc NewEnumerateNext(JSVariant in_state)
-        returns (JSBool ok,
+        returns (OperationStatus status,
                  JSVariant statep,
                  nsString idp);
 
@@ -96,24 +101,24 @@ child:
 
     rpc NewResolve(nsString id,
                    int flags)
-        returns (JSBool ok,
+        returns (OperationStatus status,
                  nullable PObjectWrapper obj2);
 
     rpc Convert(JSType type)
-        returns (JSBool ok,
+        returns (OperationStatus status,
                  JSVariant vp);
 
     rpc Call(PObjectWrapper receiver,
              JSVariant[] argv)
-        returns (JSBool ok,
+        returns (OperationStatus status,
                  JSVariant rval);
 
     rpc Construct(JSVariant[] argv)
-        returns (JSBool ok,
+        returns (OperationStatus status,
                  nullable PObjectWrapper rval);
 
     rpc HasInstance(JSVariant v)
-        returns (JSBool ok,
+        returns (OperationStatus status,
                  JSBool bp);
 };