This is a PITA under Linux, I figured this out but nor happy I had to look.
I wish Linux was like OpenBSD, where you get core files by default. This give me yet another reason to switch to OpenBSD, I only wish some other issues I am having with OpenBSD could get solved.
By this, are you referring to the behavior: "By default, this memory image is written to a file named programname.core in the working directory, provided the terminated process had write permission in the directory[...]" (from https://man.openbsd.org/core.5) ?
Also, do you know if there's a way to obtain a core file from a running process on OpenBSD? I don't see a port of gcore, and (e)gdb on OpenBSD doesn't support the generate-core-file command (it says, "Can't create a corefile").
kill -ABRT pid
should do it
However, I tried your suggestion from another terminal, and gdb appears to shield the program somehow. What ended up working is running "signal SIGABRT" from within gdb.
One thing that's still lacking is gcore's ability to take a snapshot of the core without killing the program. "Unlike after a crash, after gcore finishes its job the program remains running without any change." https://www.man7.org/linux/man-pages/man1/gcore.1.html
I've previously configured `/proc/sys/kernel/core_pattern` to generate core dumps by default (and not pipe them to a core dump collection program, which may be useful for error reporting but is rarely what I want).
There's also `gcore` for doing on-demand core dumps.
I wish it were possible to configure core dump behaviour per-process (or something similar).
ulimit -S -c unlimited
sudo sysctl -w kernel.core_pattern=core
took me a while to figure this out, HTH