gdb debug core file?

[stanton arch]

How do you debug a core file with gdb under emacs now?

I'm using emacs 24.5.1 and I can't figure out invocation to debug core file.

My emacs is starting with "gdb -i=mi" now and it seems to work fine running  
and debug some program:
 gdb -i=mi myprogram 

I've tried passing args and names to executable and core file various ways but 
haven't figured out correct way.

Thanks