> Just to clarify this, we're talking about the executable in the unique cache folder.

Unless `-of` / `-od` / `--build-only` are in play.

> Yes in any case try to delete the previous exe, if that fails report an error to the user.

So you think we should forbid the user from starting a program, opening a second terminal, editing the program and starting a second instance?

>  Imagine the surprise when you updated your sources and rdmd runs an old exe.

Yes, that needs to be avoided. However, I don't think that can happen before or after this patch.