Bug #21967: `vm_call_cfunc: cfp consistency error` while requiring `nkf.so`

• Status: Open
• Assignee: -
• Target version: -
• ruby -v: ruby 4.0.2 (2026-03-17 revision d3da9fec82) +PRISM [aarch64-linux]
• Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN

[byroot (Jean Boussier)]

I'm unfortunately unable to reproduce this consistently.

It does happen a few times a day on our production servers, and I have a few core dumps around for investigation if needed.

The crash is always while loading nknf.so.

I'm unfortunately not familiar enough with cfp to investigate this much further myself.

<PATH>/vendor/bundle/ruby/4.0.0/gems/nkf-0.2.0/lib/nkf.so: [BUG] vm_call_cfunc: cfp consistency error (0x0000ffff80779830, 0x0000ffff807797f8)
ruby 4.0.2 (2026-03-17 revision d3da9fec82) +PRISM [aarch64-linux]

-- Control frame information -----------------------------------------------
c:0032 p:---- s:0172 e:000171 l:y b:0001 TOP    [FINISH]
c:0031 p:---- s:0169 e:000168 l:y b:---- CFUNC  :require
c:0030 p:0033 s:0164 e:000163 l:n b:---- BLOCK  <PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/bu
c:0029 p:0145 s:0158 e:000157 l:y b:0001 METHOD <PATH>/vendor/bundle/ruby/4.0.0/gems/boots
c:0028 p:0026 s:0149 e:000148 l:y b:0001 TOP    <PATH>/vendor/bundle/ruby/4.0.0/gems/nkf-0 [FINISH]
c:0027 p:---- s:0146 e:000145 l:y b:---- CFUNC  :require
c:0026 p:0033 s:0141 e:000140 l:n b:---- BLOCK  <PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/bu
c:0025 p:0145 s:0135 e:000134 l:y b:0001 METHOD <PATH>/vendor/bundle/ruby/4.0.0/gems/boots
c:0024 p:0011 s:0126 e:000125 l:y b:0001 TOP    <PATH>/vendor/bundle/ruby/4.0.0/gems/mecha [FINISH]
c:0023 p:---- s:0123 e:000122 l:y b:---- CFUNC  :require
c:0022 p:0033 s:0118 e:000117 l:n b:---- BLOCK  <PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/bu
c:0021 p:0145 s:0112 e:000111 l:y b:0001 METHOD <PATH>/vendor/bundle/ruby/4.0.0/gems/boots
c:0020 p:0265 s:0103 e:000102 l:y b:0001 TOP    <PATH>/vendor/bundle/ruby/4.0.0/gems/mecha [FINISH]
c:0019 p:---- s:0100 e:000099 l:y b:---- CFUNC  :require
c:0018 p:0011 s:0095 e:000094 l:y b:0001 METHOD <internal:<PATH>/vendor/ruby-4.0.2/lib/rub
c:0017 p:0033 s:0089 e:000088 l:n b:---- BLOCK  <PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/bu
c:0016 p:0024 s:0083 e:000082 l:n b:---- BLOCK  <PATH>/vendor/bundle/ruby/4.0.0/gems/bundl [FINISH]
c:0015 p:---- s:0077 e:000076 l:y b:---- CFUNC  :each
c:0014 p:0027 s:0073 e:000072 l:n b:---- BLOCK  <PATH>/vendor/bundle/ruby/4.0.0/gems/bundl [FINISH]
c:0013 p:---- s:0069 e:000068 l:y b:---- CFUNC  :each
c:0012 p:0042 s:0065 e:000064 l:y b:0001 METHOD <PATH>/vendor/bundle/ruby/4.0.0/gems/bundl
c:0011 p:0013 s:0059 e:000058 l:y b:0001 METHOD <PATH>/vendor/bundle/ruby/4.0.0/gems/bundl
c:0010 p:0117 s:0054 e:000053 l:y b:0001 TOP    <PATH>/config/application.rb:25 [FINISH]
c:0009 p:---- s:0051 e:000050 l:y b:---- CFUNC  :require_relative
c:0008 p:0005 s:0046 e:000045 l:y b:0001 TOP    <PATH>/config/environment.rb:2 [FINISH]
c:0007 p:---- s:0043 e:000042 l:y b:---- CFUNC  :require
c:0006 p:0033 s:0038 e:000037 l:n b:---- BLOCK  <PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/bu
c:0005 p:0145 s:0032 e:000031 l:y b:0001 METHOD <PATH>/vendor/bundle/ruby/4.0.0/gems/boots
c:0004 p:0011 s:0023 e:000022 l:y b:0001 TOP    <PATH>/gems/intercom-sqs/exe/intercom-sqs: [FINISH]
c:0003 p:---- s:0011 e:000010 l:y b:---- CFUNC  :load
c:0002 p:0017 s:0006 e:000005 l:n b:---- EVAL   bin/intercom-sqs:6 [FINISH]
c:0001 p:0000 s:0003 E:001b40 l:y b:---- DUMMY  [FINISH]

-- Ruby level backtrace information ----------------------------------------
bin/intercom-sqs:6:in '<main>'
bin/intercom-sqs:6:in 'load'
<PATH>/gems/intercom-sqs/exe/intercom-sqs:6:in '<main>'
<PATH>/vendor/bundle/ruby/4.0.0/gems/bootsnap-1.22.0/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:33:in 'require'
<PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/bundled_gems.rb:60:in 'block (2 levels) in replace_require'
<PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/bundled_gems.rb:60:in 'require'
<PATH>/config/environment.rb:2:in '<main>'
<PATH>/config/environment.rb:2:in 'require_relative'
<PATH>/config/application.rb:25:in '<main>'
<PATH>/vendor/bundle/ruby/4.0.0/gems/bundler-4.0.8/lib/bundler.rb:213:in 'require'
<PATH>/vendor/bundle/ruby/4.0.0/gems/bundler-4.0.8/lib/bundler/runtime.rb:52:in 'require'
<PATH>/vendor/bundle/ruby/4.0.0/gems/bundler-4.0.8/lib/bundler/runtime.rb:52:in 'each'
<PATH>/vendor/bundle/ruby/4.0.0/gems/bundler-4.0.8/lib/bundler/runtime.rb:58:in 'block in require'
<PATH>/vendor/bundle/ruby/4.0.0/gems/bundler-4.0.8/lib/bundler/runtime.rb:58:in 'each'
<PATH>/vendor/bundle/ruby/4.0.0/gems/bundler-4.0.8/lib/bundler/runtime.rb:63:in 'block (2 levels) in require'
<PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/bundled_gems.rb:60:in 'block (2 levels) in replace_require'
<internal:<PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/rubygems/core_ext/kernel_require.rb>:37:in 'require'
<internal:<PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/rubygems/core_ext/kernel_require.rb>:37:in 'require'
<PATH>/vendor/bundle/ruby/4.0.0/gems/mechanize-2.10.0/lib/mechanize.rb:1387:in '<main>'
<PATH>/vendor/bundle/ruby/4.0.0/gems/bootsnap-1.22.0/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:33:in 'require'
<PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/bundled_gems.rb:60:in 'block (2 levels) in replace_require'
<PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/bundled_gems.rb:60:in 'require'
<PATH>/vendor/bundle/ruby/4.0.0/gems/mechanize-2.10.0/lib/mechanize/util.rb:3:in '<main>'
<PATH>/vendor/bundle/ruby/4.0.0/gems/bootsnap-1.22.0/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:33:in 'require'
<PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/bundled_gems.rb:60:in 'block (2 levels) in replace_require'
<PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/bundled_gems.rb:60:in 'require'
<PATH>/vendor/bundle/ruby/4.0.0/gems/nkf-0.2.0/lib/nkf.rb:5:in '<main>'
<PATH>/vendor/bundle/ruby/4.0.0/gems/bootsnap-1.22.0/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:33:in 'require'
<PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/bundled_gems.rb:60:in 'block (2 levels) in replace_require'
<PATH>/vendor/ruby-4.0.2/lib/ruby/4.0.0/bundled_gems.rb:60:in 'require'

-- Threading information ---------------------------------------------------
Total ractor count: 1
Ruby thread count for this ractor: 1

-- C level backtrace information -------------------------------------------
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_print_backtrace+0x8) [0xaaaab1d0964c] /ruby-4.0.2/vm_dump.c:1105
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_vm_bugreport) /ruby-4.0.2/vm_dump.c:1450
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_bug_without_die_internal+0x70) [0xaaaab1821640] /ruby-4.0.2/error.c:1098
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_bug) /ruby-4.0.2/error.c:1116
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_vm_check_ints+0x0) [0xaaaab19edc54] /ruby-4.0.2/vm_insnhelper.c:3904
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_vm_check_ints) /ruby-4.0.2/vm_core.h:2256
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_pop_frame) /ruby-4.0.2/vm_insnhelper.c:452
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_vm_pop_frame) /ruby-4.0.2/vm_insnhelper.c:461
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_call_cfunc_with_frame_) /ruby-4.0.2/vm_insnhelper.c:3906
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_call_symbol+0x32c) [0xaaaab19fed34] /ruby-4.0.2/vm_insnhelper.c:4403
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_sendish+0xc4) [0xaaaab19f3750] /ruby-4.0.2/vm_insnhelper.c:6124
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_core+0xa4) [0xaaaab1a0b994] /ruby-4.0.2/insns.def:904
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_loop+0x68) [0xaaaab19fc734] /ruby-4.0.2/vm.c:2825
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_vm_exec) /ruby-4.0.2/vm.c:2804
<PATH>/vendor/ruby-4.0.2/bin/ruby(load_iseq_eval+0x3c) [0xaaaab18a1b44] /ruby-4.0.2/load.c:774
<PATH>/vendor/ruby-4.0.2/bin/ruby(require_internal) /ruby-4.0.2/load.c:1341
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_require_string_internal+0x3c) [0xaaaab18a1f8c] /ruby-4.0.2/load.c:1451
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_require_string) /ruby-4.0.2/load.c:1437
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_f_require) /ruby-4.0.2/load.c:1048
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_cfp_consistent_p+0x0) [0xaaaab19edb00] /ruby-4.0.2/vm_insnhelper.c:3902
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_call_cfunc_with_frame_) /ruby-4.0.2/vm_insnhelper.c:3904
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_call_symbol+0x32c) [0xaaaab19fed34] /ruby-4.0.2/vm_insnhelper.c:4403
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_sendish+0xc4) [0xaaaab19f3750] /ruby-4.0.2/vm_insnhelper.c:6124
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_core+0xa4) [0xaaaab1a0b994] /ruby-4.0.2/insns.def:904
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_loop+0x68) [0xaaaab19fc734] /ruby-4.0.2/vm.c:2825
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_vm_exec) /ruby-4.0.2/vm.c:2804
<PATH>/vendor/ruby-4.0.2/bin/ruby(load_iseq_eval+0x3c) [0xaaaab18a1b44] /ruby-4.0.2/load.c:774
<PATH>/vendor/ruby-4.0.2/bin/ruby(require_internal) /ruby-4.0.2/load.c:1341
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_require_string_internal+0x3c) [0xaaaab18a1f8c] /ruby-4.0.2/load.c:1451
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_require_string) /ruby-4.0.2/load.c:1437
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_f_require) /ruby-4.0.2/load.c:1048
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_cfp_consistent_p+0x0) [0xaaaab19edb00] /ruby-4.0.2/vm_insnhelper.c:3902
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_call_cfunc_with_frame_) /ruby-4.0.2/vm_insnhelper.c:3904
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_call_symbol+0x32c) [0xaaaab19fed34] /ruby-4.0.2/vm_insnhelper.c:4403
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_sendish+0xc4) [0xaaaab19f3750] /ruby-4.0.2/vm_insnhelper.c:6124
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_core+0xa4) [0xaaaab1a0b994] /ruby-4.0.2/insns.def:904
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_loop+0x68) [0xaaaab19fc734] /ruby-4.0.2/vm.c:2825
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_vm_exec) /ruby-4.0.2/vm.c:2804
<PATH>/vendor/ruby-4.0.2/bin/ruby(load_iseq_eval+0x3c) [0xaaaab18a1b44] /ruby-4.0.2/load.c:774
<PATH>/vendor/ruby-4.0.2/bin/ruby(require_internal) /ruby-4.0.2/load.c:1341
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_require_string_internal+0x3c) [0xaaaab18a1f8c] /ruby-4.0.2/load.c:1451
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_require_string) /ruby-4.0.2/load.c:1437
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_f_require) /ruby-4.0.2/load.c:1048
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_cfp_consistent_p+0x0) [0xaaaab19edb00] /ruby-4.0.2/vm_insnhelper.c:3902
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_call_cfunc_with_frame_) /ruby-4.0.2/vm_insnhelper.c:3904
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_call_alias+0x8c) [0xaaaab19fe90c] /ruby-4.0.2/vm_insnhelper.c:4297
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_sendish+0xc4) [0xaaaab19f3750] /ruby-4.0.2/vm_insnhelper.c:6124
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_core+0xa4) [0xaaaab1a0b994] /ruby-4.0.2/insns.def:904
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_vm_exec+0x188) [0xaaaab19fc3f0] /ruby-4.0.2/vm.c:2798
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_yield+0xd0) [0xaaaab1a0131c] /ruby-4.0.2/vm.c:1871
<PATH>/vendor/ruby-4.0.2/bin/ruby(RB_FL_TEST_RAW+0x0) [0xaaaab1bf8968] /ruby-4.0.2/array.c:2754
<PATH>/vendor/ruby-4.0.2/bin/ruby(RB_FL_ANY_RAW) ./include/ruby/internal/fl_type.h:514
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_array_len) ./include/ruby/internal/core/rarray.h:259
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_ary_each) /ruby-4.0.2/array.c:2753
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_cfp_consistent_p+0x0) [0xaaaab19edb00] /ruby-4.0.2/vm_insnhelper.c:3902
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_call_cfunc_with_frame_) /ruby-4.0.2/vm_insnhelper.c:3904
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_sendish+0xc4) [0xaaaab19f3750] /ruby-4.0.2/vm_insnhelper.c:6124
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_core+0x108) [0xaaaab1a0b9f8] /ruby-4.0.2/insns.def:856
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_loop+0x68) [0xaaaab19fc734] /ruby-4.0.2/vm.c:2825
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_vm_exec) /ruby-4.0.2/vm.c:2804
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_yield+0xd0) [0xaaaab1a0131c] /ruby-4.0.2/vm.c:1871
<PATH>/vendor/ruby-4.0.2/bin/ruby(RB_FL_TEST_RAW+0x0) [0xaaaab1bf8968] /ruby-4.0.2/array.c:2754
<PATH>/vendor/ruby-4.0.2/bin/ruby(RB_FL_ANY_RAW) ./include/ruby/internal/fl_type.h:514
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_array_len) ./include/ruby/internal/core/rarray.h:259
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_ary_each) /ruby-4.0.2/array.c:2753
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_cfp_consistent_p+0x0) [0xaaaab19edb00] /ruby-4.0.2/vm_insnhelper.c:3902
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_call_cfunc_with_frame_) /ruby-4.0.2/vm_insnhelper.c:3904
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_sendish+0xc4) [0xaaaab19f3750] /ruby-4.0.2/vm_insnhelper.c:6124
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_core+0x108) [0xaaaab1a0b9f8] /ruby-4.0.2/insns.def:856
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_loop+0x68) [0xaaaab19fc734] /ruby-4.0.2/vm.c:2825
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_vm_exec) /ruby-4.0.2/vm.c:2804
<PATH>/vendor/ruby-4.0.2/bin/ruby(load_iseq_eval+0x3c) [0xaaaab18a1b44] /ruby-4.0.2/load.c:774
<PATH>/vendor/ruby-4.0.2/bin/ruby(require_internal) /ruby-4.0.2/load.c:1341
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_require_string_internal+0x58) [0xaaaab18a1e20] /ruby-4.0.2/load.c:1451
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_cfp_consistent_p+0x0) [0xaaaab19edb00] /ruby-4.0.2/vm_insnhelper.c:3902
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_call_cfunc_with_frame_) /ruby-4.0.2/vm_insnhelper.c:3904
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_sendish+0xc4) [0xaaaab19f3750] /ruby-4.0.2/vm_insnhelper.c:6124
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_core+0xa4) [0xaaaab1a0b994] /ruby-4.0.2/insns.def:904
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_vm_exec+0x188) [0xaaaab19fc3f0] /ruby-4.0.2/vm.c:2798
<PATH>/vendor/ruby-4.0.2/bin/ruby(load_iseq_eval+0x3c) [0xaaaab18a1b44] /ruby-4.0.2/load.c:774
<PATH>/vendor/ruby-4.0.2/bin/ruby(require_internal) /ruby-4.0.2/load.c:1341
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_require_string_internal+0x3c) [0xaaaab18a1f8c] /ruby-4.0.2/load.c:1451
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_require_string) /ruby-4.0.2/load.c:1437
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_f_require) /ruby-4.0.2/load.c:1048
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_cfp_consistent_p+0x0) [0xaaaab19edb00] /ruby-4.0.2/vm_insnhelper.c:3902
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_call_cfunc_with_frame_) /ruby-4.0.2/vm_insnhelper.c:3904
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_call_symbol+0x32c) [0xaaaab19fed34] /ruby-4.0.2/vm_insnhelper.c:4403
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_sendish+0xc4) [0xaaaab19f3750] /ruby-4.0.2/vm_insnhelper.c:6124
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_core+0xa4) [0xaaaab1a0b994] /ruby-4.0.2/insns.def:904
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_loop+0x68) [0xaaaab19fc734] /ruby-4.0.2/vm.c:2825
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_vm_exec) /ruby-4.0.2/vm.c:2804
<PATH>/vendor/ruby-4.0.2/bin/ruby(raise_load_if_failed+0x0) [0xaaaab18a108c] /ruby-4.0.2/load.c:851
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_load_internal) /ruby-4.0.2/load.c:853
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_f_load+0x84) [0xaaaab18a112c] /ruby-4.0.2/load.c:893
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_cfp_consistent_p+0x0) [0xaaaab19edb00] /ruby-4.0.2/vm_insnhelper.c:3902
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_call_cfunc_with_frame_) /ruby-4.0.2/vm_insnhelper.c:3904
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_sendish+0xc4) [0xaaaab19f3750] /ruby-4.0.2/vm_insnhelper.c:6124
<PATH>/vendor/ruby-4.0.2/bin/ruby(vm_exec_core+0xa4) [0xaaaab1a0b994] /ruby-4.0.2/insns.def:904
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_vm_exec+0x188) [0xaaaab19fc3f0] /ruby-4.0.2/vm.c:2798
<PATH>/vendor/ruby-4.0.2/bin/ruby(rb_ec_exec_node+0x8c) [0xaaaab1824c4c] /ruby-4.0.2/eval.c:283
<PATH>/vendor/ruby-4.0.2/bin/ruby(ruby_run_node+0x3c) [0xaaaab182716c] /ruby-4.0.2/eval.c:321
<PATH>/vendor/ruby-4.0.2/bin/ruby(main+0x70) [0xaaaab1821b30] ./main.c:42

[byroot (Jean Boussier)]

So for the record, I managed to remove our dependency on nkf, and the issue seem to have disappeared so far.

So this suggest nkf is indeed the root cause, but that is weird because I looked at the extension, and it's really not doing anything out of the ordinary: https://github.com/ruby/nkf/blob/a99304e2b2ffde94002870a67a67ad9648cead8d/ext/nkf/nkf.c#L478-L506