(gdb) bt
#0  0x00007f07e33598a5 in raise () from /lib64/libc.so.6
#1  0x00007f07e335b085 in abort () from /lib64/libc.so.6
#2  0x000000000077dcd7 in fault_handler (sn=11, si=0xccb530, ctx=0xccb400) at ../../../racket/gc2/sighand.c:99
#3  <signal handler called>
#4  0x00000000006ced43 in scheme_uncopy_stack (ok=Cannot access memory at address 0x7fff6bae5c5c
) at ../../../racket/gc2/../src/setjmpup.c:327
#5  0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6bae6a00) at ../../../racket/gc2/../src/setjmpup.c:337
#6  0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6bae70d0) at ../../../racket/gc2/../src/setjmpup.c:337
#7  0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6bae77a0) at ../../../racket/gc2/../src/setjmpup.c:337
#8  0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6bae7e70) at ../../../racket/gc2/../src/setjmpup.c:337
#9  0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6bae8540) at ../../../racket/gc2/../src/setjmpup.c:337
#10 0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6bae8c10) at ../../../racket/gc2/../src/setjmpup.c:337
#11 0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6bae92e0) at ../../../racket/gc2/../src/setjmpup.c:337
#12 0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6bae99b0) at ../../../racket/gc2/../src/setjmpup.c:337
#13 0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6baea080) at ../../../racket/gc2/../src/setjmpup.c:337
#14 0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6baea750) at ../../../racket/gc2/../src/setjmpup.c:337
#15 0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6baeae20) at ../../../racket/gc2/../src/setjmpup.c:337
<...>
#4782 0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6c2d8950) at ../../../racket/gc2/../src/setjmpup.c:337
#4783 0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6c2d9020) at ../../../racket/gc2/../src/setjmpup.c:337
#4784 0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6c2d96f0) at ../../../racket/gc2/../src/setjmpup.c:337
#4785 0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6c2d9dc0) at ../../../racket/gc2/../src/setjmpup.c:337
#4786 0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6c2da4a0) at ../../../racket/gc2/../src/setjmpup.c:337
#4787 0x00000000006cf579 in scheme_longjmpup (b=0x7f07d948af10) at ../../../racket/gc2/../src/setjmpup.c:621
#4788 0x0000000000727b32 in do_swap_thread () at ../../../racket/gc2/../src/thread.c:2544
#4789 0x000000000072d5f4 in scheme_thread_block (sleep_time=0) at ../../../racket/gc2/../src/thread.c:4752
#4790 0x0000000000454f6d in scheme_do_eval (obj=0x7f07da6aa770, num_rands=1, rands=0x7fff6c2db3b0, get_value=-1) at ../../../racket/gc2/../src/eval.c:2905
#4791 0x00000000004769d6 in apply_k () at ../../../racket/gc2/../src/fun.c:1421
#4792 0x0000000000476233 in scheme_top_level_do_worker (k=0x476901 <apply_k>, eb=1, new_thread=0, dyn_state=0x0) at ../../../racket/gc2/../src/fun.c:1253
#4793 0x0000000000475c69 in scheme_top_level_do (k=0x476901 <apply_k>, eb=1) at ../../../racket/gc2/../src/fun.c:1141
#4794 0x0000000000476aae in _apply (rator=0x7f07da6aa770, num_rands=1, rands=0x7fff6c2db3b0, multi=1, eb=1) at ../../../racket/gc2/../src/fun.c:1436
#4795 0x0000000000476b14 in scheme_apply_multi (rator=0x7f07da6aa770, num_rands=1, rands=0x7fff6c2db3b0) at ../../../racket/gc2/../src/fun.c:1448
#4796 0x0000000000738a64 in do_next_will (w=0x7f07dab26360) at ../../../racket/gc2/../src/thread.c:8009
#4797 0x0000000000738f19 in will_executor_go (argc=1, argv=0x7f07d853df08) at ../../../racket/gc2/../src/thread.c:8093
#4798 0x00007f07e3dede31 in ?? ()
#4799 0x00007fff6c2db480 in ?? ()
#4800 0x00007f07dbddfc80 in ?? ()
#4801 0x0000000500000000 in ?? ()
#4802 0x00007f07e3f716f8 in ?? ()
#4803 0x0000000200000005 in ?? ()
#4804 0x00007f07d853df20 in ?? ()
#4805 0x0000000000000004 in ?? ()
#4806 0x00007f07d853df40 in ?? ()
#4807 0x00007f07d83bedc0 in ?? ()
#4808 0x00007f07d853df20 in ?? ()
#4809 0x00007fff6c2db4e0 in ?? ()
#4810 0x00007f07d9b2f019 in ?? ()
#4811 0x0000000000000000 in ?? ()
(gdb) frame 4786
#4786 0x00000000006cedf5 in scheme_uncopy_stack (ok=0, b=0x7f07d948af10, prev=0x7fff6c2da4a0) at ../../../racket/gc2/../src/setjmpup.c:337
337
(gdb) p b
$1 = (Scheme_Jumpup_Buf *) 0x7f07d948af10
(gdb) p *b
$2 = {stack_from = 0x0, stack_copy = 0x0, stack_size = 0, stack_max_size = 0, cont = 0x0, buf = {jb = {{jb = {{__jmpbuf = {0, 0, 0, 0, 0, 0, 0, 0}, __mask_was_saved = 0,
            __saved_mask = {__val = {0 <repeats 16 times>}}}}, stack_frame = 0}}, gcvs = 0, gcvs_cnt = 0}, gc_var_stack = 0x0, external_stack = 0x0}