sometimes segfaulting with ruby 2.5.0

[doits]

Sometime after upgrade to ruby 2.5.0 I hit the following segfault:

[BUG] Segmentation fault at 0x000000000000003f
ruby 2.5.0p0 (2017-12-25 revision 61468) [x86_64-linux]

-- Control frame information -----------------------------------------------
c:0019 p:---- s:0111 e:000110 CFUNC  :packer
c:0018 p:0014 s:0107 e:000106 METHOD /cache/gems/ruby_2.5/gems/msgpack-1.2.0/lib/msgpack.rb:42
c:0017 p:0148 s:0100 e:000097 METHOD /cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/store.rb:75
c:0016 p:0009 s:0092 e:000091 METHOD /cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/store.rb:55
c:0015 p:0028 s:0088 e:000086 METHOD /cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/store.rb:47
c:0014 p:0007 s:0083 e:000082 METHOD /cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/cache.rb:138
c:0013 p:0057 s:0078 e:000077 BLOCK  /cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/cache.rb:121 [FINISH]
c:0012 p:---- s:0075 e:000074 CFUNC  :synchronize
c:0011 p:0012 s:0071 e:000070 METHOD /cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/cache.rb:115
c:0010 p:0064 s:0066 e:000065 METHOD /cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/cache.rb:14 [FINISH]
c:0009 p:---- s:0058 e:000057 CFUNC  :new
c:0008 p:0030 s:0051 e:000050 METHOD /cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache.rb:29
c:0007 p:0061 s:0042 e:000041 METHOD /cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap.rb:24
c:0006 p:0305 s:0030 e:000029 TOP    /cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/setup.rb:33 [FINISH]
c:0005 p:---- s:0020 e:000019 CFUNC  :require
c:0004 p:0055 s:0015 e:000014 TOP    /builds/stellenticket/caseman-events/config/boot.rb:4 [FINISH]
c:0003 p:---- s:0012 e:000011 CFUNC  :require_relative
c:0002 p:0046 s:0007 E:001618 EVAL   bin/rails:8 [FINISH]
c:0001 p:0000 s:0003 E:000420 (none) [FINISH]

-- Ruby level backtrace information ----------------------------------------
bin/rails:8:in `<main>'
bin/rails:8:in `require_relative'
/builds/stellenticket/caseman-events/config/boot.rb:4:in `<top (required)>'
/builds/stellenticket/caseman-events/config/boot.rb:4:in `require'
/cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/setup.rb:33:in `<top (required)>'
/cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap.rb:24:in `setup'
/cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache.rb:29:in `setup'
/cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache.rb:29:in `new'
/cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/cache.rb:14:in `initialize'
/cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/cache.rb:115:in `reinitialize'
/cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/cache.rb:115:in `synchronize'
/cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/cache.rb:121:in `block in reinitialize'
/cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/cache.rb:138:in `push_paths_locked'
/cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/store.rb:47:in `transaction'
/cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/store.rb:55:in `commit_transaction'
/cache/gems/ruby_2.5/gems/bootsnap-1.1.7/lib/bootsnap/load_path_cache/store.rb:75:in `dump_data'
/cache/gems/ruby_2.5/gems/msgpack-1.2.0/lib/msgpack.rb:42:in `pack'
/cache/gems/ruby_2.5/gems/msgpack-1.2.0/lib/msgpack.rb:42:in `packer'

-- Machine register context ------------------------------------------------
 RIP: 0x0000556fa42fe124 RBP: 0x0000556fa60f9bd0 RSP: 0x00007ffe80f38620
 RAX: 0x0000556fa60f9bd0 RBX: 0x0000556fa5e2c088 RCX: 0x0000556fa548d338
 RDX: 0x0000556fa60f9ba8 RDI: 0x000000000000002f RSI: 0x0000000000004008
  R8: 0x0000000000000000  R9: 0x0000556fa5428670 R10: 0x00000000000005c7
 R11: 0x0000556fa42fe0e0 R12: 0x0000000000000000 R13: 0x0000000000504025
 R14: 0x0000556fa5cb84a0 R15: 0x0000556fa5c3e430 EFL: 0x0000000000010202

-- C level backtrace information -------------------------------------------
/usr/local/rbenv/versions/2.5.0/bin/ruby(rb_vm_bugreport+0x53e) [0x556fa44eb1ae] vm_dump.c:703
/usr/local/rbenv/versions/2.5.0/bin/ruby(rb_bug_context+0xd1) [0x556fa44df851] error.c:580
/usr/local/rbenv/versions/2.5.0/bin/ruby(sigsegv+0x42) [0x556fa43cc5f2] signal.c:928
/lib/x86_64-linux-gnu/libpthread.so.0(0x7fa35007b390) [0x7fa35007b390]
/usr/local/rbenv/versions/2.5.0/bin/ruby(rb_hash_dup+0x44) [0x556fa42fe124] hash.c:459
/cache/gems/ruby_2.5/gems/msgpack-1.2.0/lib/msgpack/msgpack.so(msgpack_packer_ext_registry_dup+0x14) [0x7fa34df85494]
/cache/gems/ruby_2.5/gems/msgpack-1.2.0/lib/msgpack/msgpack.so(MessagePack_Factory_packer+0x6a) [0x7fa34df8046a]
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_call_cfunc+0xee) [0x556fa443da7e] vm_insnhelper.c:1918
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_call_method+0xe3) [0x556fa444c543] vm_insnhelper.c:2381
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_exec_core+0x3589) [0x556fa4446e49] insns.def:915
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_exec+0x87) [0x556fa444a897] vm.c:1778
/usr/local/rbenv/versions/2.5.0/bin/ruby(invoke_iseq_block_from_c+0x3a0) [0x556fa444b640] vm.c:979
/usr/local/rbenv/versions/2.5.0/bin/ruby(invoke_block_from_c_bh.constprop.137+0x83) [0x556fa444bb33] vm.c:1049
/usr/local/rbenv/versions/2.5.0/bin/ruby(rb_yield+0x124) [0x556fa4453154] vm.c:1094
/usr/local/rbenv/versions/2.5.0/bin/ruby(rb_ensure+0xc3) [0x556fa42d8613] eval.c:1037
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_call_cfunc+0xee) [0x556fa443da7e] vm_insnhelper.c:1918
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_call_method+0xe3) [0x556fa444c543] vm_insnhelper.c:2381
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_exec_core+0x3350) [0x556fa4446c10] insns.def:850
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_exec+0x87) [0x556fa444a897] vm.c:1778
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_call0_body.constprop.141+0x1b7) [0x556fa444d437] vm_eval.c:127
/usr/local/rbenv/versions/2.5.0/bin/ruby(rb_call0+0xe6) [0x556fa444dd26] vm_eval.c:58
/usr/local/rbenv/versions/2.5.0/bin/ruby(rb_funcallv+0x2b) [0x556fa444e4ab] vm_eval.c:589
/usr/local/rbenv/versions/2.5.0/bin/ruby(rb_class_s_new+0x21) [0x556fa43472c1] object.c:2152
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_call_cfunc+0xee) [0x556fa443da7e] vm_insnhelper.c:1918
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_call_method+0xe3) [0x556fa444c543] vm_insnhelper.c:2381
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_exec_core+0x3589) [0x556fa4446e49] insns.def:915
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_exec+0x87) [0x556fa444a897] vm.c:1778
/usr/local/rbenv/versions/2.5.0/bin/ruby(rb_load_internal0+0xc4) [0x556fa4320464] load.c:611
/usr/local/rbenv/versions/2.5.0/bin/ruby(rb_require_internal+0x6d1) [0x556fa4322131] load.c:994
/usr/local/rbenv/versions/2.5.0/bin/ruby(rb_f_require+0x13) [0x556fa43223d3] load.c:1040
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_call_cfunc+0xee) [0x556fa443da7e] vm_insnhelper.c:1918
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_call_method+0xe3) [0x556fa444c543] vm_insnhelper.c:2381
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_exec_core+0x3589) [0x556fa4446e49] insns.def:915
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_exec+0x87) [0x556fa444a897] vm.c:1778
/usr/local/rbenv/versions/2.5.0/bin/ruby(rb_load_internal0+0xc4) [0x556fa4320464] load.c:611
/usr/local/rbenv/versions/2.5.0/bin/ruby(rb_require_internal+0x6d1) [0x556fa4322131] load.c:994
/usr/local/rbenv/versions/2.5.0/bin/ruby(rb_f_require_relative+0x3c) [0x556fa432246c] load.c:1040
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_call_cfunc+0xee) [0x556fa443da7e] vm_insnhelper.c:1918
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_call_method+0xe3) [0x556fa444c543] vm_insnhelper.c:2381
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_exec_core+0x3589) [0x556fa4446e49] insns.def:915
/usr/local/rbenv/versions/2.5.0/bin/ruby(vm_exec+0x87) [0x556fa444a897] vm.c:1778
/usr/local/rbenv/versions/2.5.0/bin/ruby(ruby_exec_internal+0xc4) [0x556fa42d3184] eval.c:246
/usr/local/rbenv/versions/2.5.0/bin/ruby(ruby_run_node+0x2f) [0x556fa42d77bf] eval.c:310
/usr/local/rbenv/versions/2.5.0/bin/ruby(main+0x4b) [0x556fa42d2c2b] ./include/ruby/intern.h:295

It does not happen always, but happened already multiple times (3-4 times) on my docker CI instance running my rails test suite (so I cannot reproduce it 100 %).

This never happened on ruby 2.4.3 (and before), so it might have something to do with 2.5.0.

Anybody knows what happening or how to further debug this?

[tagomoris]

I've not identified the root cause yet, but found that we can reproduce SEGV 100% with these steps:

• rake compile
• ruby -Ilib -rmsgpack -e 'GC.stress = true; p RUBY_VERSION; f = MessagePack::Factory.new; f.register_type(0x00, Symbol);'

I'm not sure whether this problem is the same one with this issue, because these steps cause SEGV on ruby 2.4.x too.

[doits]

@tagomoris Maybe it was just a coincidence that it happened for me some days after updating to 2.5.0 for the first time.

[tagomoris]

@doits Yeah, I'm supposing that it's caused by GC behavior (very minor) change brought by Ruby 2.5.
As far as I saw your stack trace, #151 should solve that problem.
I've just released v1.2.2, including that fix. Could you try that version?

[tagomoris]

Let me close this issue. Please reopen if there still be.