Has anyone else had problems with critical sections, specificly EnterCriticalSection and LeaveCriticalSection, blowing up when running on Mac and Lazarus 1.6.4?
Note this probably would not have anything to do with the version of Lazarus, since critical sections are FPC System unit features. I assume you're using FPC 3.0.2 or trunk.
I would agree that it's probably your code, since our own code is usually the culprit. Can you isolate the critical section code in order to create a sample test app that demonstrates the problem? If so, then post a bug report.
If the code worked with a previous version of FPC, then it should still work with newer versions of FPC.
A program is only as good as the testing done on all supported platforms. If you're usually working on Windows, it's easy for changes to slip in that have not been tested on other platforms, making you think that the code used to work - some code worked, I don't doubt, but maybe not the latest code.
It's also possible for serious bugs still to be lurking in the FPC RTL, even after all of these years, hence the importance of a reproducible bug report. I recently ran into a showstopper bug in the FPC RTL, so it can happen (fortunately it was easy to fix), although that's normally the last place I would look for the source of a problem.
http://bugs.freepascal.org/view.php?id=31555