C++/CLI managed thread cleanup
- by Guillermo Prandi
Hi. I'm writing a managed C++/CLI library wrapper for the MySQL embedded server. The mysql C library requires me to call mysql_thread_init() for every thread that will be using it, and mysql_thread_end() for each thread that exits after using it.
Debugging any given VB.Net project I can see at least seven threads; I suppose my library will see only one thread if VB doesn't explicitly create worker threads itself (any confirmations on that?). However, I need clients to my library to be able to create worker threads if they need to, so my library must be thread-aware to some degree.
The first option I could think of is to expose some "EnterThread()" and "LeaveThread()" methods in my class, so the client code will explicitly call them at the beginning and before exiting their DoWork() method. This should work if (1) .Net doesn't "magically" create threads the user isn't aware of and (2) the user is careful enough to have the methods called in a try/finally structure of some sort.
However, I don't like it very much to have the user handle things manually like that, and I wonder if I could give her a hand on that matter. In a pure Win32 C/C++ DLL I do have the DllMain DLL_THREAD_ATTACH and DLL_THREAD_DETACH pseudo-events, and I could use them for calling mysql_thread_init() and mysql_thread_end() as needed, but there seem to be no such thing in C++/CLI managed code. At the expense of some performance (not much, I think) I can use TLS for detecting the "usage from a new thread" case, but I can imagine no mechanism for the thread exiting case.
So, my questions are: (1) could .net create application threads without the user being aware of them? and (2) is there any mechanism I could use similar to DLL_THREAD_ATTACH / DLL_THREAD_DETACH from managed C++/CLI?
Thanks in advance.
