The only official information about the Macro functions I am aware of can be found in a short segment in this presentation, which describes the "Macro System" as an essential part of the next compiler generation. However, the CreateMExpr shown there isn't included in Mathematica 10.4.1. (But maybe someone can find parts of it digging deeper into it?)
Install version 11.3 of the player, write your script.wl
and run wolframscript -f script.wl
If you want a GUI check https://github.com/mmatera/iwolfram and run jupyter remotely. On AWS VM run jupyter-notebook --no-browser --port=7000 then on you local machine ssh -NfL localhost:7000:localhost:6001 <IP>)
I can confirm this issue.
For example, the following code will hang the front end of v12.0.0.
(* !!! SAVE ALL YOUR WORK BEFORE RUNNING THIS !!! *)
For[i = 0, True, i++, Print[i]]
As noted by Lucas in comments, one can use Task Manager/Activity Monitor to terminate WolframKernel process (but not Mathematica process). This way one will loose all evaluation ...