Answers to related questions all suggest using
lsof or checking under
/proc/NPID/, which is not helpful for when the process is already gone and only its core-dump remains.
However, it should be possible to obtain the file-descriptors opened by the late process, along with the filesystem-identifier(s) and inode-number for each.
I realize, this is OS-specific, but I only need it for (modern) Linux... I suppose, it needs to be a script fed to gdb, but what are the global symbols to look for?