dogbert@dogbert-VirtualBox ~/repos/rakudo $ ./perl6-gdb-m -I /home/dogbert/repos/rakudo/install/share/perl6/site/lib mapper.p6
================================================================================================
This is Rakudo Perl 6 running in the GNU debugger, which often allows the user to generate useful back-
traces to debug or report issues in Rakudo, the MoarVM backend or the currently running code.

This Rakudo version is 2017.02.55.g.320.c.2.fb.46 built on MoarVM version 2017.02.7.g.3.d.859008,
running on ubuntu (14.04.3.LTS.Trusty.Tahr) / linux (3.19.0.32.generic)

Type `bt full` to generate a backtrace if applicable, type `q` to quit or `help` for help.
------------------------------------------------------------------------------------------------
Reading symbols from /home/dogbert/repos/rakudo/install/bin/moar...done.
Starting program: /home/dogbert/repos/rakudo/install/bin/moar --execname=./perl6-gdb-m --libpath=/home/dogbert/repos/rakudo/install/share/nqp/lib --libpath=/home/dogbert/repos/rakudo/install/share/nqp/lib --libpath=. /home/dogbert/repos/rakudo/perl6.moarvm --nqp-lib=blib -I /home/dogbert/repos/rakudo/install/share/perl6/site/lib mapper.p6
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/i386-linux-gnu/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
p6recont_ro (tc=0x804c450, cur_op=0xb6991fea "\004") at src/vm/moar/ops/perl6_ops.c:268
268	        if (!MVM_is_null(tc, desc) && ((Rakudo_ContainerDescriptor *)desc)->rw) {
(gdb) bt
#0  p6recont_ro (tc=0x804c450, cur_op=0xb6991fea "\004") at src/vm/moar/ops/perl6_ops.c:268
#1  0xb7c3819d in MVM_interp_run (tc=tc@entry=0x804c450, initial_invoke=initial_invoke@entry=0xb7d045c0 <toplevel_initial_invoke>, invoke_data=0x1) at src/core/interp.c:5633
#2  0xb7d05196 in MVM_vm_run_file (instance=0x804c008, filename=0xbffff2b4 "/home/dogbert/repos/rakudo/perl6.moarvm") at src/moar.c:309
#3  0x08048d39 in main (argc=10, argv=0xbffff004) at src/main.c:201
(gdb) f 0
#0  p6recont_ro (tc=0x804c450, cur_op=0xb6991fea "\004") at src/vm/moar/ops/perl6_ops.c:268
268	        if (!MVM_is_null(tc, desc) && ((Rakudo_ContainerDescriptor *)desc)->rw) {
(gdb) p MVM_dump_backtrace(tc)
   at <unknown>:1  (./CORE.setting.moarvm:return)
 from <unknown>:1  (./CORE.setting.moarvm:return)
 from SETTING::src/core/Any-iterable-methods.pm:1506  (./CORE.setting.moarvm:pull-one)
 from SETTING::src/core/Any-iterable-methods.pm:362  (./CORE.setting.moarvm:pull-one)
 from SETTING::src/core/Any-iterable-methods.pm:362  (./CORE.setting.moarvm:pull-one)
 from SETTING::src/core/Any-iterable-methods.pm:362  (./CORE.setting.moarvm:pull-one)
 from SETTING::src/core/Rakudo/Internals.pm:1717  (./CORE.setting.moarvm:pull-one)
 from SETTING::src/core/Iterator.pm:55  (./CORE.setting.moarvm:push-all)
 from SETTING::src/core/Rakudo/Internals.pm:1766  (./CORE.setting.moarvm:coremap)
 from SETTING::src/core/Rakudo/Internals.pm:1685  (./CORE.setting.moarvm:coremap)
 from SETTING::src/core/metaops.pm:538  (./CORE.setting.moarvm:deepmap)
 from SETTING::src/core/metaops.pm:536  (./CORE.setting.moarvm:deepmap)
 from <unknown>:1  (./CORE.setting.moarvm:HYPER)
 from SETTING::src/core/metaops.pm:419  (./CORE.setting.moarvm:HYPER)
 from <unknown>:1  (./CORE.setting.moarvm:dispatch:<hyper>)
 from mapper.p6:22  (<ephemeral file>:methods)
 from mapper.p6:6  (<ephemeral file>:<unit>)
 from mapper.p6:1  (<ephemeral file>:<unit-outer>)
 from gen/moar/stage2/NQPHLL.nqp:1587  (/home/dogbert/repos/rakudo/install/share/nqp/lib/NQPHLL.moarvm:eval)
 from gen/moar/stage2/NQPHLL.nqp:1790  (/home/dogbert/repos/rakudo/install/share/nqp/lib/NQPHLL.moarvm:evalfiles)
 from gen/moar/stage2/NQPHLL.nqp:1684  (/home/dogbert/repos/rakudo/install/share/nqp/lib/NQPHLL.moarvm:command_eval)
 from src/Perl6/Compiler.nqp:42  (./blib/Perl6/Compiler.moarvm:command_eval)
 from gen/moar/stage2/NQPHLL.nqp:1658  (/home/dogbert/repos/rakudo/install/share/nqp/lib/NQPHLL.moarvm:command_line)
 from gen/moar/main.nqp:47  (/home/dogbert/repos/rakudo/perl6.moarvm:MAIN)
 from gen/moar/main.nqp:38  (/home/dogbert/repos/rakudo/perl6.moarvm:<mainline>)
 from <unknown>:1  (/home/dogbert/repos/rakudo/perl6.moarvm:<main>)
 from <unknown>:1  (/home/dogbert/repos/rakudo/perl6.moarvm:<entry>)
$1 = void