How do I guarantee fast shutdown of my win32 app?

Question

I\'ve got a C++ Win32 application that has a number of threads that might be busy doing IO (HTTP calls, etc) when the user wants to shutdown the application. Currently, I p

Answer 1

*NULL = 0 is the fastest way. if you don't want to crash, call exit() or its win32 equivalent.

Answer 2

Instruct the user to unplug the computer. Short of that, you have to abandon your asynchronous activities to the wind. Or is that HWIND? I can never remember in C++. Of course, you could take the middle road and quickly note in a text file or reg key what action was abandoned so that the next time the program runs it can take up that action again automatically or ask the user if they want to do so. Depending on what data you lose when you abandon the asynch action, you may not be able to do that. If you're interacting with the user, you may want to consider a dialog or some UI interaction that explains why its taking so long.

Personally, I prefer the instruction to the user to just unplug the computer. :)

Answer 3

You can call TerminateProcess - this will stop the process immediately, without notifying anyone and without waiting for anything.

Answer 4

I once had a similar problem, albeit in Visual Basic 6: threads from an app would connect to different servers, download some data, perform some operations looping upon that data, and store on a centralized server the result.

Then, new requirement was that threads should be stoppable from main form. I accomplished this in an easy though dirty fashion, by having the threads stop after N loops (equivalent roughly to half a second) to try to open a mutex with a specific name. Upon success, they immediately stopped whatever they were doing and quit, continued otherwise.

This mutex was created only by the main form, once it was created all the threads would soon close themselves. The disadvantage was that user needed to manually specify it wanted to run the threads again - another button to "Enable threads to run" accomplished this by releasing the mutex :D

This trick is guaranteed to work for mutex operations are atomic. Problem is you're never sure a thread really closed - a failure in the logic of handling the "openMutex succeeded" case could mean it never ends. You also don't know when/if all the threads have closed (assuming your code is right, this would take roughly the same time it takes for the loops to stop and "listen").

With VB's "apartment" model of multi-threading it's somewhat difficult to send info from the threads to the main app back and forth, it's much easier to "fire and forget" or to send it only from the main app to the thread. Thus, the need of these kind of long-cuts. Using C++ you're free to use your multi-threading model, so these constraints might not apply to you.

Answer 5

Whatever you do, do NOT use TerminateThread, especially on anything that could be in OS HTTP calls. You could potentially break IE until reboot.

Change all of your IO to an asynchronous or non-blocking model so that they can watch for termination events.