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Concurrency::task.wait() throws invalid_operation

Concurrency::task.wait() throws invalid_operation exception: "Illegal to wait on a task in a Windows Runtime STA."

This exception occurs since ~14th November 2022 and seems to be Microsoft update related.

The exception does not occur, when building in Debug mode. Edit: it was true only for some Visual Studio versions. The latest release do throw the exception regardless of Debug or Release modes.

The code runs in a C++ application as managed-C++.

Any known Microsoft issues in this direction? Edit: the exception seems to be correct but it never showed up until some updates.

Solution

  • The issue appears if single threaded COM initialization via CoInitializeEx(NULL, COINIT_APARTMENTTHREADED); or CoInitialize(NULL); is done prior to calling Concurrency::task.wait().

    The issue can be fixed by initializing COM with

    CoInitializeEx(NULL, COINIT_MULTITHREADED);

    or

    Windows::Foundation::Initialize(RO_INIT_MULTITHREADED);

    If you want to call Concurrency::task.wait() on a thread which is already initialized as COINIT_APARTMENTTHREADED and you cannot change it - start your concurrency task in a new thread via e.g. std::thread.