[racket] Debugging a seg fault

I working on a small test program using Jay McCarthy's zmq FFI bindings.

I'm getting a segfault with this message:

SIGSEGV MAPERR si_code 1 fault on addr 0x285

Is there any guidance on how to spot the cause?  Here's what I have done so far
run racket with gdb - as gdb racket

In the gdb console...

handle SIGSEGV nostop
handle SIGSEGV noprint

(those last two seem to be necessary for my script to run at all)

And finally I run my racket file in gdb as follows
run -tm example.rkt

I then get this message, after my code actually starts:

SIGSEGV MAPERR si_code 1 fault on addr 0x285

Program received signal SIGABRT, Aborted.
[Switching to Thread 0x7fffe77fe700 (LWP 20186)]
0x00007ffff713e1e5 in __GI_raise (sig=sig at entry=6)
    at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
56 ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.


The nice thing about this problem is that it is consistently reproducible.

Any advice?

Chad