Segfault in MVMCallCapture.gc_mark

[niner]

nine@sphinx:~/rakudo/nqp/MoarVM (master=)> perl6-gdb-m -e 'class SQLString { }; my $stringy = Str.^find_method("Stringy"); my $handler = $stringy.wrap(method () { SQLString.new(:str(callsame)) }); say "foo".Stringy'
================================================================================================
This Rakudo version is 2016.09.33.ge.12.ebb.9 built on MoarVM version 2016.09.1.gdebb.859,
running on opensuse (Tumbleweed) / linux (4.6.3.1.default)
------------------------------------------------------------------------------------------------
Reading symbols from /home/nine/rakudo/install/bin/moar...done.
Starting program: /home/nine/rakudo/install/bin/moar --execname=/home/nine/rakudo/install/bin/perl6-gdb-m --libpath=/home/nine/rakudo/install/share/nqp/lib --libpath=/home/nine/rakudo/install/share/perl6/lib --libpath=/home/nine/rakudo/install/share/perl6/runtime /home/nine/rakudo/install/share/perl6/runtime/perl6.moarvm -e class\ SQLString\ \{\ \}\;\ my\ \$stringy\ =\ Str.\^find_method\(\"Stringy\"\)\;\ my\ \$handler\ =\ \$stringy.wrap\(method\ \(\)\ \{\ SQLString.new\(:str\(callsame\)\)\ \}\)\;\ say\ \"foo\".Stringy
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff78fcb7f in gc_mark (tc=0x6037c0, st=0x606830, data=0x386a0d8, worklist=0x39f9cc0) at src/6model/reprs/MVMCallCapture.c:55
55                  if (flag_map[flag] & MVM_CALLSITE_ARG_NAMED) {
(gdb) l
50              MVMArgProcContext *ctx = body->apc;
51              MVMuint8  *flag_map = ctx->arg_flags ? ctx->arg_flags : ctx->callsite->arg_flags;
52              MVMuint16  count = ctx->arg_count;
53              MVMuint16  i, flag;
54              for (i = 0, flag = 0; i < count; i++, flag++) {
55                  if (flag_map[flag] & MVM_CALLSITE_ARG_NAMED) {
56                      /* Current position is name, then next is value. */
57                      MVM_gc_worklist_add(tc, worklist, &ctx->args[i].s);
58                      i++;
59                  }
(gdb) p flag_map
$1 = (MVMuint8 *) 0x3800000035 <error: Cannot access memory at address 0x3800000035>
(gdb) p ctx->arg_flags
$2 = (MVMCallsiteEntry *) 0x0
(gdb) p ctx->callsite->arg_flags
$3 = (MVMCallsiteEntry *) 0x3800000035 <error: Cannot access memory at address 0x3800000035>
(gdb) bt full
#0  0x00007ffff78fcb7f in gc_mark (tc=0x6037c0, st=0x606830, data=0x386a0d8, worklist=0x39f9cc0) at src/6model/reprs/MVMCallCapture.c:55
        ctx = 0x30bfd80
        count = 1
        i = 0
        flag = 0
        flag_map = 0x3800000035 <error: Cannot access memory at address 0x3800000035>
        body = 0x386a0d8
#1  0x00007ffff78c27b0 in MVM_gc_mark_collectable (tc=0x6037c0, worklist=0x39f9cc0, new_addr=0x386a0c0) at src/gc/collect.c:399
        new_addr_obj = 0x386a0c0
        i = 0
        sc_idx = 0
        __PRETTY_FUNCTION__ = "MVM_gc_mark_collectable"
#2  0x00007ffff78c1602 in process_worklist (tc=0x6037c0, worklist=0x39f9cc0, wtp=0x7fffffffbcd0, gen=0 '\000') at src/gc/collect.c:313
        item = 0x7ffff667dbb8
        item_gen2 = 0 '\000'
        to_gen2 = 1 '\001'
        gen2 = 0x603d00
        item_ptr = 0x34ec5b8
        new_addr = 0x386a0c0
        gen2count = 46
        __PRETTY_FUNCTION__ = "process_worklist"
#3  0x00007ffff78c1142 in MVM_gc_collect (tc=0x6037c0, what_to_do=0 '\000', gen=0 '\000') at src/gc/collect.c:129
        fromspace = 0x7ffff663b010
        tospace = 0x7ffff4d9c010
        worklist = 0x39f9cc0
        wtp = {num_target_threads = 0, target_work = 0x0}
#4  0x00007ffff78bc821 in run_gc (tc=0x6037c0, what_to_do=0 '\000') at src/gc/orchestrate.c:304
        other = 0x6037c0
        gen = 0 '\000'
        i = 0
        n = 1
#5  0x00007ffff78bcd05 in MVM_gc_enter_from_allocator (tc=0x6037c0) at src/gc/orchestrate.c:438
        last_starter = 0x622c80
        num_threads = 0
#6  0x00007ffff78bd0b7 in MVM_gc_allocate_nursery (tc=0x6037c0, size=280) at src/gc/allocation.c:32
        allocated = 0x7ffff6a3ae08
#7  0x00007ffff78bcfa5 in MVM_gc_allocate (tc=0x6037c0, size=280) at src/gc/allocation.h:13
No locals.
#8  0x00007ffff78bd133 in MVM_gc_allocate_zeroed (tc=0x6037c0, size=280) at src/gc/allocation.c:49
No locals.
#9  0x00007ffff78bd39e in MVM_gc_allocate_frame (tc=0x6037c0) at src/gc/allocation.c:99
        f = 0x6037c0
#10 0x00007ffff7892317 in MVM_frame_force_to_heap (tc=0x6037c0, frame=0x7ffff7fd45a8) at src/core/frame.c:657
        promoted = 0x7ffff6a3ae08
        cur_to_promote = 0x7ffff7fd4378
        new_cur_frame = 0x7ffff4df3460
        update_caller = 0x7ffff4df3578
        result = 0x7ffff4df3460
#11 0x00007ffff5e76b08 in p6finddispatcher (tc=0x6037c0, cur_op=0x30ab7e4 "") at src/vm/moar/ops/perl6_ops.c:543
        ctx = 0x2291390
#12 0x00007ffff788a574 in MVM_interp_run (tc=0x6037c0, initial_invoke=0x7ffff797de79 <toplevel_initial_invoke>, invoke_data=0x6738b8) at src/core/interp.c:5599
        op_before = 0x30ab7e4 ""
        record = 0xf18118
        op = 1029
        LABELS = {0x7ffff7860023 <MVM_interp_run+214>, 0x7ffff786005f <MVM_interp_run+274>, 0x7ffff7860061 <MVM_interp_run+276>, 0x7ffff7860061 <MVM_interp_run+276>, 0x7ffff786007c <MVM_interp_run+303>, 
          0x7ffff78600ff <MVM_interp_run+434>, 0x7ffff786011a <MVM_interp_run+461>, 0x7ffff78601a2 <MVM_interp_run+597>, 0x7ffff7860237 <MVM_interp_run+746>, 0x7ffff78602c7 <MVM_interp_run+890>, 
          0x7ffff786035a <MVM_interp_run+1037>, 0x7ffff78603ed <MVM_interp_run+1184>, 0x7ffff786047e <MVM_interp_run+1329>, 0x7ffff7860512 <MVM_interp_run+1477>, 0x7ffff78605a6 <MVM_interp_run+1625>, 
          0x7ffff7860637 <MVM_interp_run+1770>, 0x7ffff78606c6 <MVM_interp_run+1913>, 0x7ffff7860756 <MVM_interp_run+2057>, 0x7ffff78607e5 <MVM_interp_run+2200>, 0x7ffff7860874 <MVM_interp_run+2343>, 
          0x7ffff7860904 <MVM_interp_run+2487>, 0x7ffff7860993 <MVM_interp_run+2630>, 0x7ffff7860a29 <MVM_interp_run+2780>, 0x7ffff7860abf <MVM_interp_run+2930>, 0x7ffff7860b38 <MVM_interp_run+3051>, 
          0x7ffff7860bec <MVM_interp_run+3231>, 0x7ffff7860ca0 <MVM_interp_run+3411>, 0x7ffff7860d64 <MVM_interp_run+3607>, 0x7ffff7860e28 <MVM_interp_run+3803>, 0x7ffff7860f05 <MVM_interp_run+4024>, 
          0x7ffff7860fe2 <MVM_interp_run+4245>, 0x7ffff78610b6 <MVM_interp_run+4457>, 0x7ffff786118a <MVM_interp_run+4669>, 0x7ffff7861249 <MVM_interp_run+4860>, 0x7ffff7861308 <MVM_interp_run+5051>, 
          0x7ffff7861431 <MVM_interp_run+5348>, 0x7ffff78615fa <MVM_interp_run+5805>, 0x7ffff78617ef <MVM_interp_run+6306>, 0x7ffff78618a1 <MVM_interp_run+6484>, 0x7ffff7861955 <MVM_interp_run+6664>, 
          0x7ffff7861a07 <MVM_interp_run+6842>, 0x7ffff7861ae7 <MVM_interp_run+7066>, 0x7ffff7861b93 <MVM_interp_run+7238>, 0x7ffff7861c3f <MVM_interp_run+7410>, 0x7ffff7861ceb <MVM_interp_run+7582>, 
          0x7ffff7861d97 <MVM_interp_run+7754>, 0x7ffff7861d97 <MVM_interp_run+7754>, 0x7ffff7861db2 <MVM_interp_run+7781>, 0x7ffff7861e64 <MVM_interp_run+7959>, 0x7ffff7861f12 <MVM_interp_run+8133>, 
          0x7ffff786272f <MVM_interp_run+10210>, 0x7ffff7862861 <MVM_interp_run+10516>, 0x7ffff78628ec <MVM_interp_run+10655>, 0x7ffff7862983 <MVM_interp_run+10806>, 0x7ffff7862a0e <MVM_interp_run+10945>, 
          0x7ffff7862a99 <MVM_interp_run+11084>, 0x7ffff7862b03 <MVM_interp_run+11190>, 0x7ffff7862bbe <MVM_interp_run+11377>, 0x7ffff7862c79 <MVM_interp_run+11564>, 0x7ffff7862d34 <MVM_interp_run+11751>, 
          0x7ffff7862def <MVM_interp_run+11938>, 0x7ffff7862eaa <MVM_interp_run+12125>, 0x7ffff7862f65 <MVM_interp_run+12312>, 0x7ffff7863053 <MVM_interp_run+12550>, 0x7ffff7863108 <MVM_interp_run+12731>, 
          0x7ffff78631c0 <MVM_interp_run+12915>, 0x7ffff7863276 <MVM_interp_run+13097>, 0x7ffff78633f8 <MVM_interp_run+13483>, 0x7ffff78634b3 <MVM_interp_run+13670>, 0x7ffff78635ac <MVM_interp_run+13919>, 
          0x7ffff786366a <MVM_interp_run+14109>, 0x7ffff78636fd <MVM_interp_run+14256>, 0x7ffff78637be <MVM_interp_run+14449>, 0x7ffff7863833 <MVM_interp_run+14566>, 0x7ffff78638a8 <MVM_interp_run+14683>, 
          0x7ffff786391d <MVM_interp_run+14800>, 0x7ffff7863992 <MVM_interp_run+14917>, 0x7ffff7863a47 <MVM_interp_run+15098>, 0x7ffff7863afc <MVM_interp_run+15279>, 0x7ffff7863bb1 <MVM_interp_run+15460>, 
          0x7ffff7863c44 <MVM_interp_run+15607>, 0x7ffff7863cf9 <MVM_interp_run+15788>, 0x7ffff7863dae <MVM_interp_run+15969>, 0x7ffff7863ec5 <MVM_interp_run+16248>, 0x7ffff7863f5e <MVM_interp_run+16401>, 
          0x7ffff7864086 <MVM_interp_run+16697>, 0x7ffff78641c8 <MVM_interp_run+17019>, 0x7ffff7864292 <MVM_interp_run+17221>, 0x7ffff786435c <MVM_interp_run+17423>, 0x7ffff786441a <MVM_interp_run+17613>, 
          0x7ffff78644d8 <MVM_interp_run+17803>, 0x7ffff7864596 <MVM_interp_run+17993>, 0x7ffff7864654 <MVM_interp_run+18183>, 0x7ffff786474a <MVM_interp_run+18429>, 0x7ffff7864803 <MVM_interp_run+18614>, 
          0x7ffff78648bc <MVM_interp_run+18799>, 0x7ffff7864975 <MVM_interp_run+18984>, 0x7ffff7864a2e <MVM_interp_run+19169>, 0x7ffff7864b47 <MVM_interp_run+19450>, 0x7ffff7864be5 <MVM_interp_run+19608>, 
          0x7ffff7864cb1 <MVM_interp_run+19812>, 0x7ffff7864d82 <MVM_interp_run+20021>, 0x7ffff7864e2c <MVM_interp_run+20191>, 0x7ffff7864ed6 <MVM_interp_run+20361>, 0x7ffff7864f80 <MVM_interp_run+20531>, 
          0x7ffff786502a <MVM_interp_run+20701>, 0x7ffff78650d4 <MVM_interp_run+20871>, 0x7ffff786517e <MVM_interp_run+21041>, 0x7ffff7865228 <MVM_interp_run+21211>, 0x7ffff78652d2 <MVM_interp_run+21381>, 
          0x7ffff78653a3 <MVM_interp_run+21590>, 0x7ffff7865459 <MVM_interp_run+21772>, 0x7ffff7865501 <MVM_interp_run+21940>, 0x7ffff78655ab <MVM_interp_run+22110>, 0x7ffff7865655 <MVM_interp_run+22280>, 
          0x7ffff78656ff <MVM_interp_run+22450>, 0x7ffff78657b5 <MVM_interp_run+22632>, 0x7ffff786585f <MVM_interp_run+22802>, 0x7ffff7865909 <MVM_interp_run+22972>, 0x7ffff78659b3 <MVM_interp_run+23142>, 
          0x7ffff7865a4d <MVM_interp_run+23296>, 0x7ffff7865ae3 <MVM_interp_run+23446>, 0x7ffff7865b86 <MVM_interp_run+23609>, 0x7ffff7865c35 <MVM_interp_run+23784>, 0x7ffff7865cd8 <MVM_interp_run+23947>, 
          0x7ffff7865d80 <MVM_interp_run+24115>, 0x7ffff7865e3b <MVM_interp_run+24302>, 0x7ffff7865ef6 <MVM_interp_run+24489>, 0x7ffff7865f85 <MVM_interp_run+24632>, 0x7ffff786601d <MVM_interp_run+24784>, 
          0x7ffff78660b7 <MVM_interp_run+24938>, 0x7ffff786614f <MVM_interp_run+25090>, 0x7ffff78661e7 <MVM_interp_run+25242>, 0x7ffff7866272 <MVM_interp_run+25381>, 0x7ffff7866302 <MVM_interp_run+25525>, 
          0x7ffff786639f <MVM_interp_run+25682>, 0x7ffff78664c6 <MVM_interp_run+25977>, 0x7ffff7866608 <MVM_interp_run+26299>, 0x7ffff786674a <MVM_interp_run+26621>, 0x7ffff786688c <MVM_interp_run+26943>, 
          0x7ffff78669ce <MVM_interp_run+27265>, 0x7ffff7866a5a <MVM_interp_run+27405>, 0x7ffff7866afd <MVM_interp_run+27568>, 0x7ffff7866bb0 <MVM_interp_run+27747>, 0x7ffff7866c53 <MVM_interp_run+27910>, 
          0x7ffff7866cf6 <MVM_interp_run+28073>, 0x7ffff7866dda <MVM_interp_run+28301>, 0x7ffff7866ec0 <MVM_interp_run+28531>, 0x7ffff7866fa4 <MVM_interp_run+28759>, 0x7ffff7867088 <MVM_interp_run+28987>, 
          0x7ffff7867143 <MVM_interp_run+29174>, 0x7ffff786720e <MVM_interp_run+29377>, 0x7ffff78672c9 <MVM_interp_run+29564>, 0x7ffff7867384 <MVM_interp_run+29751>, 0x7ffff7867480 <MVM_interp_run+30003>, 
          0x7ffff786757e <MVM_interp_run+30257>, 0x7ffff786767a <MVM_interp_run+30509>, 0x7ffff7867776 <MVM_interp_run+30761>, 0x7ffff7867817 <MVM_interp_run+30922>, 0x7ffff78678a7 <MVM_interp_run+31066>, 
          0x7ffff786793b <MVM_interp_run+31214>, 0x7ffff7867a45 <MVM_interp_run+31480>, 0x7ffff7867ac5 <MVM_interp_run+31608>, 0x7ffff7867b68 <MVM_interp_run+31771>, 0x7ffff7867c0c <MVM_interp_run+31935>, 
          0x7ffff7867d2f <MVM_interp_run+32226>, 0x7ffff7867e52 <MVM_interp_run+32517>, 0x7ffff7867f43 <MVM_interp_run+32758>, 0x7ffff7868033 <MVM_interp_run+32998>, 0x7ffff7868177 <MVM_interp_run+33322>, 
          0x7ffff7868268 <MVM_interp_run+33563>, 0x7ffff7868325 <MVM_interp_run+33752>, 0x7ffff78683e2 <MVM_interp_run+33941>, 0x7ffff786849f <MVM_interp_run+34130>, 0x7ffff786854c <MVM_interp_run+34303>, 
          0x7ffff78685f9 <MVM_interp_run+34476>, 0x7ffff78686a6 <MVM_interp_run+34649>, 0x7ffff7868761 <MVM_interp_run+34836>, 0x7ffff78687d6 <MVM_interp_run+34953>, 0x7ffff7868844 <MVM_interp_run+35063>, 
          0x7ffff78688fc <MVM_interp_run+35247>, 0x7ffff7868989 <MVM_interp_run+35388>, 0x7ffff7868a79 <MVM_interp_run+35628>, 0x7ffff7868b1c <MVM_interp_run+35791>, 0x7ffff7868ba8 <MVM_interp_run+35931>, 
          0x7ffff7868c34 <MVM_interp_run+36071>, 0x7ffff7868d3e <MVM_interp_run+36337>, 0x7ffff7868e7a <MVM_interp_run+36653>, 0x7ffff7868fb6 <MVM_interp_run+36969>, 0x7ffff7869102 <MVM_interp_run+37301>, 
          0x7ffff786923e <MVM_interp_run+37617>, 0x7ffff786947f <MVM_interp_run+38194>, 0x7ffff78695b7 <MVM_interp_run+38506>, 0x7ffff78696d6 <MVM_interp_run+38793>, 0x7ffff7869891 <MVM_interp_run+39236>, 
          0x7ffff7869975 <MVM_interp_run+39464>, 0x7ffff7869a3a <MVM_interp_run+39661>, 0x7ffff7869aac <MVM_interp_run+39775>, 0x7ffff7869b45 <MVM_interp_run+39928>, 0x7ffff7869c0a <MVM_interp_run+40125>...}
        cur_op = 0x30ab7e4 ""
        bytecode_start = 0x30ab790 <incomplete sequence \367>
        reg_base = 0x39d1370
        cu = 0x663280
        cur_callsite = 0x7ffff7dd8b20 <null_args_callsite>
#13 0x00007ffff797df9c in MVM_vm_run_file (instance=0x603010, filename=0x7fffffffdc84 "/home/nine/rakudo/install/share/perl6/runtime/perl6.moarvm") at src/moar.c:304
        tc = 0x6037c0
        cu = 0x661e80
#14 0x000000000040128f in main (argc=8, argv=0x7fffffffd638) at src/main.c:191
        instance = 0x603010
        input_file = 0x7fffffffdc84 "/home/nine/rakudo/install/share/perl6/runtime/perl6.moarvm"
        executable_name = 0x7fffffffdbbc "/home/nine/rakudo/install/bin/perl6-gdb-m"
        lib_path = {0x7fffffffdbf0 "/home/nine/rakudo/install/share/nqp/lib", 0x7fffffffdc22 "/home/nine/rakudo/install/share/perl6/lib", 0x7fffffffdc56 "/home/nine/rakudo/install/share/perl6/runtime", 0x0, 
          0xc2 <error: Cannot access memory at address 0xc2>, 0x7fffffffd52f "", 0x7fffffffd52e "", 
          0x7ffff74032f5 <handle_intel+101> "H\205\300uyL\211\351L\211\342D\211\376\211\357\350\266\374\377\377H\205\300ud\213t$\bL\211\351L\211\342\211\357\350\240\374\377\377H\205\300uND9t$\fA\215V\001v0A\211ָ\002"}
        dump = 0
        full_cleanup = 0
        argi = 6
        lib_path_i = 3
        flag = -2

[LLFourn]

note: This is related to https://rt.perl.org/Public/Bug/Display.html?id=128553

@niner I'm so glad you were able to golf this. I had a huge project that was suffering from it and I couldn't figure out what was causing the segfaults. Removed the .wrap and it works again (so far).

[jnthn]

Was almost certainly the same issues as #612 which has now finally been hunted down and fixed.