I’m in the process of upgrading an application from 18.2 to 19.1. And in the new version I’m faced with an error 4390 that was not there before.

It stems from this definition in Winuser.pkg:

External_Function SendMessage 'SendMessageA' User32.dll ;
Handle hwnd Integer uMsg Longptr wParam Longptr lParam Returns Longptr

And in my code I have:

Function sendMessage tSendMessageRequest Request Returns tSendMessageResponse

The error is:

- Error 4390: C:\Work\ApplicationBroker\3.7\AppSrc\Messaging.wo (ln 62) Illegal method name definition SENDMESSAGE is already defined as an external_function

In 18.2 both Winuser.pkg and my code was the same, but no error. What has changed, and how do I get rid of this error? I can’t change the name of my function, because it is part of a public web service API.