In PowerBuilder 7 or earlier, if an error occurs that is not caught by an Error or ExternalException event, the application's SystemError event is triggered immediately. If there is no code associated with the SystemError event, the application is terminated. Otherwise, after the SystemError event executes, control returns to the location in the code where the error occurred.
In PowerBuilder 8 and later, if an error occurs that is not caught by the exception handling mechanism or by an Error or ExternalException event, the script terminates and the call stack is unwound. If the error occurs as the result of a Triggerevent call in a script, the calling script terminates and the call stack is unwound. In most cases, the SystemError event is not triggered until the call stack becomes empty. If an event of a response window caused the error, the SystemError event is triggered as soon as the response window event completes.
Because of this change in behavior, code that follows the statement that caused the error is not executed after the SystemError event is fired, as it would have been in previous releases. This change has a major impact on applications that rely on the previous behavior of returning control to the script where the error occurred. Code that relies on this behavior must be modified in PowerBuilder 8 and later.
You can handle potential errors by wrapping code that might cause an error in a try-catch block to prevent the SystemError event from being triggered when an execution error occurs. It is still advisable to code the SystemError event to handle any uncaught exceptions. You should not allow the application to continue after the SystemError event is invoked. The SystemError event should clean up and halt the application.
