After reinstalling my OS X, my system had these permissions set on "/cores" folder:

drwxr-xr-x 2 root wheel 64 Aug 23 18:01 cores

Which would make our crash handler call to abort() fail to generate the core file, so hs_err_pid crash log file would end up lying:

# Core dump will be written. Default location: /cores/core.64980
...
Dumping core ...

as core file would NOT be written.

The solution is for the user to do:

sudo chmod a+w /cores

but it would be nice if hs_err_pid would say something about it.

For example it already says this:

# No core dump will be written. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again

if ulimit is not set, so it should say something similar if wrong permissions are set on "/cores" folder, that prohibit core file dumps.