WinForm Timer time interval is less than execution time

If the interval of SetTimer is T, its response to the event OnTimer code executes over time is T, and t>t.
So, one time not executed, the next time, how will the program execute?

Possible situations:
1. Discard the code that has not been executed, and start the new execution;
2, do not discard, the timer message into the message queue queued, wait until the original code execution, immediately start a new execution;
3, re-enter, is the original also continue to execute, at the same time start a new implementation;

Answer: The second one, or, the first one is discarded. But the drop is that the message queue is full and the second message doesn't go in.

is generally the second case.

WinForm Timer time interval is less than execution time