Help with confusing C code in loader?

[walt]

I'm trying to debug a problem in /boot/loader but I'm stumped by
this line in sys/boot/common/module.c:

error = (file_formats[i]->l_load)(filename, loadaddr, &fp);

This seems to refer to a line in common/bootstrap.h:

int (* l_load)(char *filename, u_int64_t dest, struct preloaded_file **result);

And that's where I lose the thread.  I can't figure out what the
(* l_load) means because 'l_load' doesn't seem to be defined in
any obvious place.

Any clues most welcome.