1. The wisdom of the Internet has not been able to figure out how to generate a core dump on MacOS 10.15.2 (Catalina).  The usual set of enabling steps can be performed without error, but still no core dump.

2. Until today I believed that there was no way to generate a Cygwin core dump.  I know now that there is, but I may not be able to test it until Monday.  I'll let you know, and hopefully that will provide insight into the MacOS problem as well.

3.  I will try to work further on the MacOS libffi problem (which surfaces when you do --disable-jit to bypass the above problem) to convince MacOS to use GNU libffi rather than the native one.  It probably has to do with pkg-config, which I barely understand.

"All problems are config problems."

John Cowan          http://vrici.lojban.org/~cowan        cowan@ccil.org
We are lost, lost.  No name, no business, no Precious, nothing.  Only empty.
Only hungry: yes, we are hungry.  A few little fishes, nassty bony little
fishes, for a poor creature, and they say death.  So wise they are; so just,
so very just.  --Gollum