Third party code is modifying the FPU control word

Question

The introduction - the long and boring part

(The question is at the end)

I am getting severe head aches over a third party COM component that keeps changing the

Answer 1

Although FP control word is per-thread, dllmain functions are called when new threads are created, i don't think you can avoid this short of going to a new process.

I suggest you spin-off a new process to run the COM and chat with the process with your favorite inter-process communication method (e.g. windows message, out-of-proc COM, named pipe, socket, etc). In this way the COM server is free to do all kinds of damage (including crashing itself) without bring your host process down.

Another idea is to write a DLL whose sole purpose is to reset the FPU in its DllMain and load it immediately after the offending DLL. Windows is probably using the loading order to call DllMain when new threads are created, including threads created by the COM server. Note this depends on Windows's internal behavior. Also the COM server may actually depends on fp exceptions since it enables them. Disabling FP exceptions may causes the COM server to behave unexpectedly.