David Heffernan

It's all proscribed by ieee754.

Are you talking about maths, or talking about ieee754?

Well, this depends on whether or not exceptions are masked.

I'm not recommending anything. I'm just stating how ieee754 defines these operations.

Well, for ieee754 the former is NaN and the latter is +inf.

Do yourself a favour and check whether exceptions are masked in the two programs at the point where exveptions are raised.

Probably you are calling some code, typically in a DLL, which changes the floating point control status to mask exceptions. Delphi default is for them to be unmasked, but most other Windows dev tools mask them.

Is this based on the WhatsApp API?

Well, Delphi's floating point library isn't threadsafe so they can have a party together!!

The code fails to compile in XE7 with the same E2512 error. I consider a set type to be a non-nullable value type so this must be a defect.

SetWindowDisplayAffinity(Application.MainFormHandle You really need to be calling this method from CreateWnd because of VCL window recreation. Also it's kinda odd that you would use MainFormHandle from a method of the main form. Why not use Handle? But it's important to move that code to CreateWnd.

You are on subscription when 10.4.2 lands, and then the subscription expires a month later.

Reading Marco's article on the recently released patches for 10.4.2 I noticed this text: Is that right? If you don't keep an active update subscription, you aren't entitled to bug fixes?

Neither is more suited than the other for multi-threaded programs. I don't think your usage scenario is particularly challenging or unusual as you seem to think.

You have already had numerous suggestions that meet all your requirements.