Issue #21854 has been updated by jhawthorn (John Hawthorn). Status changed from Open to Third Party's Issue I would argue that this is a bug in ruby-prof. `RUBY_INTERNAL_EVENT_NEWOBJ` is an internal event, so the semantics of exactly when it fires and the state the object is in are not documented and may change. In Ruby 4.0 (specifically https://github.com/ruby/ruby/commit/74075617b17ab80db74a5e7c1c8515601a8ce6f4) we moved initialization of the three VALUEs following `flags` and `klass` to after this runs, so `RUBY_INTERNAL_EVENT_NEWOBJ` sees these objects in a not fully initialized state (which was always the case, they're just _more_ uninitialized now). I think ruby-prof should not do this. It doesn't make sense to call memsize_of on object immediately after it's allocated anyways. For almost all types that `memsize_of` returns something other than the slot size those values aren't filled in until after the NEWOBJ event fires (even on 3.4 and below), so whatever results this is reporting are bogus. IMO Long term nothing should be supported on the object passed to `RUBY_INTERNAL_EVENT_NEWOBJ` other than making note of the object's address. We had some similar discussions in #21710 ---------------------------------------- Bug #21854: ruby-prof breaks on 4.0.1 https://bugs.ruby-lang.org/issues/21854#change-116230 * Author: cfis (Charlie Savage) * Status: Third Party's Issue * ruby -v: ruby 4.0.1 (2026-01-13 revision e04267a14b) +PRISM [x64-mswin64_140] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- ruby-prof breaks on 4.0.x with segmentation faults. See failing github pipelines: https://github.com/ruby-prof/ruby-prof/actions/runs/21465420365/job/61826466... (note the failures for ruby 3.x are some test that fail, not segmentation faults). Tracking this down, I focused on the `measure_memory_test.rb` file. I have attached the traceback below. What is happening is: * Get a tracearg event (https://github.com/ruby-prof/ruby-prof/blob/master/ext/ruby_prof/rp_profile....) * Get a measurement - time, memory, etc. - https://github.com/ruby-prof/ruby-prof/blob/master/ext/ruby_prof/rp_measurem... * Get the tracearg object - https://github.com/ruby-prof/ruby-prof/blob/master/ext/ruby_prof/rp_measure_... * Call rb_obj_memsize_of - https://github.com/ruby-prof/ruby-prof/blob/master/ext/ruby_prof/rp_measure_... * For a T_DATA object you end up in in gc.c
case T_DATA: size += rb_objspace_data_type_memsize(obj); break;
`rb_objspace_data_type_memsize` causes a segmentation fault. Running in a debugger, with a breakpoing set in `rb_objspace_data_type_memsize`: ``` c RTYPEDDATA_TYPE(obj) 0x332d747365676964 {wrap_struct_name=??? function={dmark=??? dfree=??? dsize=??? ...} parent=??? ...} wrap_struct_name: <Unable to read memory> function: {dmark=??? dfree=??? dsize=??? ...} parent: <Unable to read memory> data: <Unable to read memory> flags: <Unable to read memory> ``` The tracearg type is `RUBY_INTERNAL_EVENT_NEWOBJ`. Here is the traceback. This is from a MSVC build, but you can see in the gitlab pipelines the same happens on Ubuntu. ```bash -- C level backtrace information ------------------------------------------- C:\WINDOWS\SYSTEM32\ntdll.dll(NtWaitForSingleObject+0x14) [0x00007FF817DA1C44] C:\WINDOWS\System32\KERNELBASE.dll(WaitForSingleObjectEx+0xaf) [0x00007FF814F2BC5F] C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_print_backtrace+0x3e) [0x00007FFEEBB01F92] C:\Source\ruby-4.0.1-mswin\vm_dump.c:1129 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_vm_bugreport+0x223) [0x00007FFEEBB021BB] C:\Source\ruby-4.0.1-mswin\vm_dump.c:1453 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_bug_for_fatal_signal+0x75) [0x00007FFEEB9BE779] C:\Source\ruby-4.0.1-mswin\error.c:1131 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(sigsegv+0x3d) [0x00007FFEEBAFAF91] C:\Source\ruby-4.0.1-mswin\signal.c:948 C:\WINDOWS\System32\ucrtbase.dll(seh_filter_exe+0x84) [0x00007FF81591E8A4] C:\msys64\usr\local\ruby-4.0.1-mswin\bin\ruby.exe(`__scrt_common_main_seh'::`1'::filt$0+0x16) [0x00007FF7B95D1B4C] D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:304 C:\WINDOWS\SYSTEM32\VCRUNTIME140.dll(_C_specific_handler+0x9d) [0x00007FFFF400F55D] C:\WINDOWS\SYSTEM32\ntdll.dll(_chkstk+0x9f) [0x00007FF817DA62FF] C:\WINDOWS\SYSTEM32\ntdll.dll(RtlLocateExtendedFeature+0x597) [0x00007FF817C52327] C:\WINDOWS\SYSTEM32\ntdll.dll(KiUserExceptionDispatcher+0x2e) [0x00007FF817DA5C3E] C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_obj_memsize_of+0x1dc) [0x00007FFEEB9A2C8C] C:\Source\ruby-4.0.1-mswin\gc.c:2351 C:\Source\ruby-prof\ext\ruby_prof\ruby_prof.so(measure_memory+0x51) [0x00007FFFA8427161] C:\Source\ruby-prof\ext\ruby_prof\rp_measure_memory.c:23 C:\Source\ruby-prof\ext\ruby_prof\ruby_prof.so(prof_measure+0x1a) [0x00007FFFA8425D8A] C:\Source\ruby-prof\ext\ruby_prof\rp_measurement.c:38 C:\Source\ruby-prof\ext\ruby_prof\ruby_prof.so(prof_event_hook+0x43) [0x00007FFFA842AC23] C:\Source\ruby-prof\ext\ruby_prof\rp_profile.c:200 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(tp_call_trace+0x26) [0x00007FFEEBA41E12] C:\Source\ruby-4.0.1-mswin\vm_trace.c:1300 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(exec_hooks_body+0x74) [0x00007FFEEBA3FCA4] C:\Source\ruby-4.0.1-mswin\vm_trace.c:457 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_exec_event_hooks+0x4a) [0x00007FFEEBA40326] C:\Source\ruby-4.0.1-mswin\vm_trace.c:543 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_gc_event_hook+0xc1) [0x00007FFEEB99DE35] C:\Source\ruby-4.0.1-mswin\gc.c:241 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(newobj_of+0x17c) [0x00007FFEEB99C348] C:\Source\ruby-4.0.1-mswin\gc.c:1014 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(typed_data_alloc+0xb6) [0x00007FFEEB9A565A] C:\Source\ruby-4.0.1-mswin\gc.c:1102 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_data_typed_object_zalloc+0x3b) [0x00007FFEEB99D877] C:\Source\ruby-4.0.1-mswin\gc.c:1125 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_managed_id_table_create+0x21) [0x00007FFEEBA2AF2D] C:\Source\ruby-4.0.1-mswin\id_table.c:375 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(callable_method_entry_or_negative+0x299) [0x00007FFEEB9C434D] C:\Source\ruby-4.0.1-mswin\vm_method.c:1918 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(callable_method_entry+0x9) [0x00007FFEEB9C4081] C:\Source\ruby-4.0.1-mswin\vm_method.c:1937 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_populate_cc+0x2a) [0x00007FFEEB9E1CF2] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:2155 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_vm_search_method_slowpath+0x7d) [0x00007FFEEB9D0D21] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:2299 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_search_method_slowpath0+0x20) [0x00007FFEEB9E261C] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:2321 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_sendish+0x14e) [0x00007FFEEB9E2B2E] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:6123 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_exec_core+0x1f41) [0x00007FFEEB9DCA85] C:\Source\ruby-4.0.1-mswin\vm_exec.c:101 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_vm_exec+0x101) [0x00007FFEEB9CF7C9] C:\Source\ruby-4.0.1-mswin\vm.c:2801 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(invoke_block_from_c_bh+0x2eb) [0x00007FFEEB9C688B] C:\Source\ruby-4.0.1-mswin\vm.c:1834 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_yield_with_cref+0x93) [0x00007FFEEB9E41BF] C:\Source\ruby-4.0.1-mswin\vm.c:1874 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_yield+0x55) [0x00007FFEEB9D1125] C:\Source\ruby-4.0.1-mswin\vm_eval.c:1380 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_protect+0x14a) [0x00007FFEEB9B8DFA] C:\Source\ruby-4.0.1-mswin\eval.c:1127 C:\Source\ruby-prof\ext\ruby_prof\ruby_prof.so(prof_profile_instance+0x58) [0x00007FFFA842C128] C:\Source\ruby-prof\ext\ruby_prof\rp_profile.c:820 C:\Source\ruby-prof\ext\ruby_prof\ruby_prof.so(prof_profile_class+0x2f) [0x00007FFFA842C19F] C:\Source\ruby-prof\ext\ruby_prof\rp_profile.c:845 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_call_cfunc_with_frame_+0x14a) [0x00007FFEEB9D52DA] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:3904 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_call_cfunc_with_frame+0x29) [0x00007FFEEB9D5189] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:3949 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_call_cfunc_other+0xbc) [0x00007FFEEB9D5154] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:3976 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_call_cfunc+0x103) [0x00007FFEEB9D4E67] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:4057 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_call_method_each_type+0x67b) [0x00007FFEEB9D7503] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:4888 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_call_method+0x14c) [0x00007FFEEB9D6E68] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:5052 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_sendish+0x163) [0x00007FFEEB9E2B43] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:6134 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_exec_core+0x1f41) [0x00007FFEEB9DCA85] C:\Source\ruby-4.0.1-mswin\vm_exec.c:101 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_vm_exec+0x101) [0x00007FFEEB9CF7C9] C:\Source\ruby-4.0.1-mswin\vm.c:2801 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(invoke_block_from_c_bh+0x2eb) [0x00007FFEEB9C688B] C:\Source\ruby-4.0.1-mswin\vm.c:1834 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_yield_with_cref+0x93) [0x00007FFEEB9E41BF] C:\Source\ruby-4.0.1-mswin\vm.c:1874 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_yield+0x55) [0x00007FFEEB9D1125] C:\Source\ruby-4.0.1-mswin\vm_eval.c:1380 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_ary_each+0x7f) [0x00007FFEEBA1A083] C:\Source\ruby-4.0.1-mswin\array.c:2754 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_call_cfunc_with_frame_+0x14a) [0x00007FFEEB9D52DA] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:3904 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_call_cfunc_with_frame+0x29) [0x00007FFEEB9D5189] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:3949 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_sendish+0x163) [0x00007FFEEB9E2B43] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:6134 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_exec_core+0x1f41) [0x00007FFEEB9DCA85] C:\Source\ruby-4.0.1-mswin\vm_exec.c:101 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_vm_exec+0x101) [0x00007FFEEB9CF7C9] C:\Source\ruby-4.0.1-mswin\vm.c:2801 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(invoke_block_from_c_bh+0x2eb) [0x00007FFEEB9C688B] C:\Source\ruby-4.0.1-mswin\vm.c:1834 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_yield_with_cref+0x93) [0x00007FFEEB9E41BF] C:\Source\ruby-4.0.1-mswin\vm.c:1874 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_yield+0x55) [0x00007FFEEB9D1125] C:\Source\ruby-4.0.1-mswin\vm_eval.c:1380 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_ary_collect+0xa4) [0x00007FFEEBA18F38] C:\Source\ruby-4.0.1-mswin\array.c:3767 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_call_cfunc_with_frame_+0x14a) [0x00007FFEEB9D52DA] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:3904 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_call_cfunc_with_frame+0x29) [0x00007FFEEB9D5189] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:3949 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_sendish+0x163) [0x00007FFEEB9E2B43] C:\Source\ruby-4.0.1-mswin\vm_insnhelper.c:6134 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_exec_core+0x1f41) [0x00007FFEEB9DCA85] C:\Source\ruby-4.0.1-mswin\vm_exec.c:101 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_vm_exec+0x101) [0x00007FFEEB9CF7C9] C:\Source\ruby-4.0.1-mswin\vm.c:2801 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(vm_invoke_proc+0x304) [0x00007FFEEB9DF6D8] C:\Source\ruby-4.0.1-mswin\vm.c:1944 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_vm_invoke_proc+0x95) [0x00007FFEEB9CFCE9] C:\Source\ruby-4.0.1-mswin\vm.c:1967 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_proc_call_kw+0x70) [0x00007FFEEBAADD6C] C:\Source\ruby-4.0.1-mswin\proc.c:1134 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(exec_end_procs_chain+0x3d) [0x00007FFEEB9B5B4D] C:\Source\ruby-4.0.1-mswin\eval_jump.c:106 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_ec_exec_end_proc+0x13b) [0x00007FFEEB9B73AF] C:\Source\ruby-4.0.1-mswin\eval_jump.c:122 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_ec_teardown+0x11e) [0x00007FFEEB9B789A] C:\Source\ruby-4.0.1-mswin\eval.c:158 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(rb_ec_cleanup+0x260) [0x00007FFEEB9B6C68] C:\Source\ruby-4.0.1-mswin\eval.c:211 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\x64-vcruntime140-ruby400.dll(ruby_run_node+0x4d) [0x00007FFEEB9B998D] C:\Source\ruby-4.0.1-mswin\eval.c:321 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\ruby.exe(wmain+0x52) [0x00007FF7B95D1052] C:\Source\ruby-4.0.1-mswin\main.c:48 C:\msys64\usr\local\ruby-4.0.1-mswin\bin\ruby.exe(__scrt_common_main_seh+0x10c) [0x00007FF7B95D126C] D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288 C:\WINDOWS\System32\KERNEL32.DLL(BaseThreadInitThunk+0x17) [0x00007FF816AEE8D7] ``` -- https://bugs.ruby-lang.org/