On 1/25/21, 2:49 PM, "mpiwg-tools on behalf of Raffenetti, Kenneth J. via mpiwg-tools" <[email protected] on behalf of [email protected]> wrote: On 1/25/21, 12:44 PM, "mpiwg-tools on behalf of Raffenetti, Kenneth J. via mpiwg-tools" <[email protected] on behalf of [email protected]> wrote: On 1/25/21, 11:46 AM, "Marc-André Hermanns" <[email protected]> wrote: For me (although not explicitly defined in the text) that would imply that the dropped callback is only invoked once the library is in a state where a callback (and user_data) for the same level is defined and could be invoked. Does this make sense and clarify your concerns? Do you think this need more clarification in the text? I see. Yes, that makes sense for my implementation issue. I may have spoken too soon. I'm looking at pg 763, ln 37 (Handling Dropped Events): If an event occurs...[and] no callback function meeting the required callback safety level is registered, the event data may be dropped. To discover such data loss, the user can set a handler function for a specific event-registration handle. If a callback function meeting the required safety level is not registered, how do I decide which user buffer to provide to the dropped handler? Oh, so if I am reading your clarification correctly above, you are saying I should not invoke the dropped handler until a callback for that safety level has been registered. It is possible then that I might never call the dropped handler. Should I be managing dropped event counts for all safety levels? Ken