Filter from SetUnhandledExceptionFilter not capturing C++ exceptions from threads started with _beginthread on windows server 2022

Question

We have found a the change in behaviour of the SetUnhandledExceptionFilter API call. On windows server 2016, this enables any uncaught C++ exceptions to be handled by a registered filter, including on our worker threads. In our filter callback we have alternative handling, including stopping the applications from terminating, but on windows server 2022, our filter doesn't get called for C++ exceptions on our worker threads, but the application is terminated instead.

There is no mention of a change in behaviour of this on certain windows versions in the windows API documentation.

Some investigation has shown this seems to be related to different versions of UCRT.dll (universal C run time) between different windows server OS versions.

And also in relation to any threads created using _beginthread/_beginthreadex It seems this has been changed to _beginthread to now be noexcept() in behaviour - similar to std::thread behaviour. But the problem is that this is not based which version of the C++ compiler/toolset or C/C++ libraries that we compile/link against, but what the OS shipped UCRT.DLL is compiler against, and so relates to the windows OS version.

We are needing to upgrade some servers to windows server 2022 from 2016, but this is changing the behaviour of out existing applications, that rely on the SetUnhandledExceptionFilter behaviour to catch any C++ exceptions. And so this is blocking our migration. This applications need to be running continually (except for allowed shutdown times on weekends), and so crashes/shutdown are major incidents.

Answer 1

#include <windows.h>

#include <stdio.h>

#include <eh.h>

// Define a custom exception filter function

LONG WINAPI CustomUnhandledExceptionFilter(EXCEPTION_POINTERS* ExceptionInfo) {

// Handle exceptions here

// For example, log the exception or perform custom actions

printf("Unhandled exception occurred!\n");

return EXCEPTION_EXECUTE_HANDLER;

}

int main() {

// Set the custom unhandled exception filter

SetUnhandledExceptionFilter(CustomUnhandledExceptionFilter);

// Create a worker thread

HANDLE thread = (HANDLE)_beginthread([](void* param) {

    // Worker thread code

    // For example, simulate an exception

    throw std::runtime_error("Simulated exception");

}, 0, nullptr);

WaitForSingleObject(thread, INFINITE);

CloseHandle(thread);

return 0;

}