multithreading - Is it dangerous to use synchronize in a non-VCL application?

Question

If Delphi code was written with synchronize to serialize access to the main VCL thread, but this code then is used in a non-VCL application, will it synchronize with the main thread of the application or just have no effect at all?

---

Example:

procedure TMyThread.Execute;
begin

  // ... other code

  Synchronize(SomeMethod);

  // ...

end;

Let's assume

• it is a non-VCL application which has a main thread which executes in an endless loop (or until terminated)
• the main thread does not call CheckSynchronize directly or in a WakeMainThread handler
• a secondary thread runs and executes Synchronize(SomeMethod) like in the example above

Will the thread hang on the Synchronize(SomeMethod) line?

Answer 1

TThread provides facilities for non-VCL programs to check the synchronization queue, so they can continue to use multithreaded libraries that expect to synchronize their methods. This is described in the documentation for CheckSynchronize. Remember that it's the application's job to check the queue, not your library's.

As long as the application honors its part of the contract, your use of Synchronize should be fine. If it doesn't, though, then your program will not work correctly, but I don't know what exact symptoms to expect. Hanging certainly sounds plausible.