this is my "intermittent core dump during a live demo" badge

Parrot

(gdb) bt
#0  0x00000000014001c0 in ?? ()
#1  0x00007f146f5e6c9b in Parrot_StringBuilder_nci_append_format (interp=0x1398460, _self=<value optimized out>)
   from /home/leto/git/rakudo/parrot_install/lib/libparrot.so.2.6.0
#2  0x00007f146f577a4a in Parrot_NCI_invoke (interp=0x1398460, _self=0x140dd80, next=0x7f146c039fd8)
   from /home/leto/git/rakudo/parrot_install/lib/libparrot.so.2.6.0
#3  0x00007f146f554131 in runops_fast_core (interp=0x1398460, runcore_unused=<value optimized out>, pc=0x898e420) at src/runcore/cores.c:514
#4  0x00007f146f553b6d in runops_int (interp=0x1398460, offset=<value optimized out>) at src/runcore/main.c:237
#5  0x00007f146f52b3de in runops (interp=<value optimized out>, offs=<value optimized out>) at src/call/ops.c:127
#6  0x00007f146f527591 in Parrot_pcc_invoke_from_sig_object (interp=0x1398460, sub_obj=<value optimized out>, call_object=<value optimized out>)
    at src/call/pcc.c:325
#7  0x00007f146f51c85d in Parrot_ext_call (interp=0x1398460, sub_pmc=0x8213930, signature=<value optimized out>) at src/extend.c:322
#8  0x00007f146f8a46da in plperl6_run (interp=0x1398460, code=0x6eda4f0, fcinfo=0x7fff6a94b440, numargs=1) at plparrot.c:488
#9  0x00007f146f8a48a4 in plperl6_func_handler (fcinfo=<value optimized out>) at plparrot.c:228
#10 plperl6_call_handler (fcinfo=<value optimized out>) at plparrot.c:427
#11 0x000000000057c1e2 in ExecMakeFunctionResult (fcache=<value optimized out>, econtext=<value optimized out>, isNull=0x81cf968 "Q~", isDone=0x81cfaa8)
    at execQual.c:1827
#12 0x00000000005771c6 in ExecTargetList (projInfo=<value optimized out>, isDone=<value optimized out>) at execQual.c:5079
#13 ExecProject (projInfo=<value optimized out>, isDone=<value optimized out>) at execQual.c:5294
#14 0x000000000058e4ab in ExecResult (node=0x81cebe0) at nodeResult.c:155
#15 0x0000000000576748 in ExecProcNode (node=0x81cebe0) at execProcnode.c:355
#16 0x00000000005752fe in ExecutePlan (queryDesc=0x11aa848, direction=144237728, count=0) at execMain.c:1190
#17 standard_ExecutorRun (queryDesc=0x11aa848, direction=144237728, count=0) at execMain.c:280
#18 0x000000000063e947 in PortalRunSelect (portal=0x110f028, forward=<value optimized out>, count=0, dest=0x10f54c8) at pquery.c:952
#19 0x000000000063fdf0 in PortalRun (portal=<value optimized out>, count=<value optimized out>, isTopLevel=<value optimized out>, 
    dest=<value optimized out>, altdest=<value optimized out>, completionTag=<value optimized out>) at pquery.c:796
#20 0x000000000063c12b in exec_simple_query (query_string=<value optimized out>) at postgres.c:1052
#21 0x000000000063d16b in PostgresMain (argc=<value optimized out>, argv=<value optimized out>, username=<value optimized out>) at postgres.c:3869
#22 0x0000000000602841 in BackendRun () at postmaster.c:3535
#23 BackendStartup () at postmaster.c:3223
#24 ServerLoop () at postmaster.c:1431
#25 0x000000000060515d in PostmasterMain (argc=3, argv=0x10ec8d0) at postmaster.c:1092
#26 0x00000000005a57c0 in main (argc=3, argv=0x10ec8c0) at main.c:188