On: D compilation is too slow and I am forking the compiler

[Asooka]

Not exactly a fork, but Emacs is (famous/notorious) for saving its initial environment by basically coredumping and loading the coredump on startup if the startup files haven't changed:

https://lwn.net/Articles/673724/

http://emacshorrors.com/posts/unexecute.html(quite unflattering as the link suggests, but factually accurate nonetheless)