Don't ignore any errors returned by PostCreate. Also, don't override an exception if one is already reported, as the further away from the original problem we get, the less precise the error message will be. bug 326497, r=brendan sr=shaver

js/src/xpconnect/src/xpcprivate.h

@@ -2515,6 +2515,7 @@ private:
 
     static void BuildAndThrowException(JSContext* cx, nsresult rv, const char* sz);
     static JSBool ThrowExceptionObject(JSContext* cx, nsIException* e);
+    static JSBool CheckForPendingException(nsresult result, XPCCallContext &ccx);
 
 private:
     static JSBool sVerbose;

js/src/xpconnect/src/xpcthrower.cpp

@@ -49,11 +49,41 @@ void
 XPCThrower::Throw(nsresult rv, JSContext* cx)
 {
     const char* format;
+    if(JS_IsExceptionPending(cx))
+        return;
     if(!nsXPCException::NameAndFormatForNSResult(rv, nsnull, &format))
         format = "";
     BuildAndThrowException(cx, rv, format);
 }
 
+/*
+ * If there has already been an exception thrown, see if we're throwing the
+ * same sort of exception, and if we are, don't clobber the old one. ccx
+ * should be the current call context.
+ */
+// static
+JSBool
+XPCThrower::CheckForPendingException(nsresult result, XPCCallContext &ccx)
+{
+    nsXPConnect* xpc = nsXPConnect::GetXPConnect();
+    if(!xpc)
+        return JS_FALSE;
+
+    nsCOMPtr<nsIException> e;
+    xpc->GetPendingException(getter_AddRefs(e));
+    if(!e)
+        return JS_FALSE;
+    xpc->SetPendingException(nsnull);
+
+    nsresult e_result;
+    if(NS_FAILED(e->GetResult(&e_result)) || e_result != result)
+        return JS_FALSE;
+
+    if(!ThrowExceptionObject(ccx, e))
+        JS_ReportOutOfMemory(ccx);
+    return JS_TRUE;
+}
+
 // static
 void
 XPCThrower::Throw(nsresult rv, XPCCallContext& ccx)
@@ -61,6 +91,9 @@ XPCThrower::Throw(nsresult rv, XPCCallContext& ccx)
     char* sz;
     const char* format;
 
+    if(CheckForPendingException(rv, ccx))
+        return;
+
     if(!nsXPCException::NameAndFormatForNSResult(rv, nsnull, &format))
         format = "";
 
@@ -91,24 +124,8 @@ XPCThrower::ThrowBadResult(nsresult rv, nsresult result, XPCCallContext& ccx)
     *  call. So we'll just throw that exception into our JS.
     */
 
-    nsXPConnect* xpc = nsXPConnect::GetXPConnect();
-    if(xpc)
-    {
-        nsCOMPtr<nsIException> e;
-        xpc->GetPendingException(getter_AddRefs(e));
-        if(e)
-        {
-            xpc->SetPendingException(nsnull);
-
-            nsresult e_result;
-            if(NS_SUCCEEDED(e->GetResult(&e_result)) && e_result == result)
-            {
-                if(!ThrowExceptionObject(ccx, e))
-                    JS_ReportOutOfMemory(ccx);
-                return;
-            }
-        }
-    }
+    if(CheckForPendingException(result, ccx))
+        return;
 
     // else...
 

js/src/xpconnect/src/xpcwrappednative.cpp

@@ -461,8 +461,10 @@ XPCWrappedNative::GetNewOrUsed(XPCCallContext& ccx,
         XPCNativeScriptableInfo* si = wrapper->GetScriptableInfo();
         if(si && si->GetFlags().WantPostCreate())
         {
-            si->GetCallback()->
-                PostCreate(wrapper, ccx, wrapper->GetFlatJSObject());
+            rv = si->GetCallback()->
+                     PostCreate(wrapper, ccx, wrapper->GetFlatJSObject());
+            if(NS_FAILED(rv))
+                return rv;
         }
     }