I get segfaults on random basis in the below program I wrote for issue41321 while trying to use Ctrl-C to stop the program. I used faulthandler but couldn't get to the exact case where it occurs. I tested it on Python 3.9 from deadsnakes ppa and it crashes. I tried using gdb to get a backtrace but using ctrl-C is caught by gdb. I tried using "handle SIGINT noprint pass" to ensure the ctrl-C is passed to the program by gdb and attached below is a backtrace during a sample segfault. I am wording it as during zoneinfo creation but isolated object creation under an infinite loop where ctrl-c is passed doesn't trigger this. Feel free to modify this as needed and also to add more since I am not good with debugging C issues.

import datetime
import zoneinfo

timezones = zoneinfo.available_timezones()
for year in range(1900, 2020):
    for tz in timezones:
        d1 = datetime.datetime(year, 5, 4, 7, 13, 22, tzinfo=zoneinfo.ZoneInfo(tz)).timestamp()
        d2 = datetime.datetime(year, 5, 4, 0, 0, 0, tzinfo=zoneinfo.ZoneInfo(tz)).timestamp()
        diff = d1 - d2
        if diff != 26002:
            print(year, diff, tz)

    for tz in timezones:
        d1 = datetime.datetime(year, 5, 2, 7, 13, 22, tzinfo=zoneinfo.ZoneInfo(tz)).timestamp()
        d2 = datetime.datetime(year, 5, 2, 0, 0, 0, tzinfo=zoneinfo.ZoneInfo(tz)).timestamp()
        diff = d1 - d2
        if diff != 26002:
            print("Diff using second day", year, diff, tz)

$ python3.9 -X faulthandler ../backups/bpo41321.py
^CFatal Python error: Segmentation fault

Current thread 0x00007f23bb2b9740 (most recent call first):
  File "/root/cpython/../backups/bpo41321.py", line 7 in <module>
[1]    1234 segmentation fault (core dumped)  python3.9 -X faulthandler ../backups/bpo41321.py

Debug build on master branch

$  ./python -X faulthandler ../backups/bpo41321.py
^Cpython: Objects/typeobject.c:3244: _PyType_Lookup: Assertion `!PyErr_Occurred()' failed.
Fatal Python error: Aborted

Current thread 0x00007f28c2256080 (most recent call first):
  File "/root/cpython/../backups/bpo41321.py", line 14 in <module>
[1]    1386 abort (core dumped)  ./python -X faulthandler ../backups/bpo41321.py


(gdb) r
Starting program: /root/cpython/python ../backups/bpo41321.py
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
^C
Program received signal SIGSEGV, Segmentation fault.
zoneinfo_no_cache (cls=<optimized out>, args=<optimized out>, 
    kwargs=<optimized out>) at /root/cpython/Modules/_zoneinfo.c:380
380	    PyObject *out = zoneinfo_new_instance(cls, key);
(gdb) bt
#0  zoneinfo_no_cache (cls=<optimized out>, args=<optimized out>, 
    kwargs=<optimized out>) at /root/cpython/Modules/_zoneinfo.c:380
#1  0x00007ffff65ff826 in zoneinfo_new (
    type=0x7ffff6801480 <PyZoneInfo_ZoneInfoType>, args=<optimized out>, 
    kw=<optimized out>) at /root/cpython/Modules/_zoneinfo.c:274
#2  0x000055555562a635 in type_call (
    type=type@entry=0x7ffff6801480 <PyZoneInfo_ZoneInfoType>, 
    args=args@entry=0x7ffff6fb7520, kwds=kwds@entry=0x0)
    at Objects/typeobject.c:1020
#3  0x00005555555c3018 in _PyObject_MakeTpCall (
    tstate=tstate@entry=0x555555b2c350, 
    callable=callable@entry=0x7ffff6801480 <PyZoneInfo_ZoneInfoType>, 
    args=args@entry=0x7ffff6f20df8, nargs=<optimized out>, keywords=0x0)
    at Objects/call.c:191
#4  0x00005555555ab48b in _PyObject_VectorcallTstate (kwnames=<optimized out>, 
    nargsf=<optimized out>, args=<optimized out>, callable=<optimized out>, 
    tstate=<optimized out>) at ./Include/cpython/abstract.h:112
#5  PyObject_Vectorcall (kwnames=<optimized out>, nargsf=<optimized out>, 
    args=<optimized out>, callable=<optimized out>)
    at ./Include/cpython/abstract.h:123
#6  call_function (tstate=tstate@entry=0x555555b2c350, 
    pp_stack=pp_stack@entry=0x7fffffffdf30, oparg=<optimized out>, 
    kwnames=kwnames@entry=0x0) at Python/ceval.c:5121
#7  0x00005555555b17dd in _PyEval_EvalFrameDefault (tstate=<optimized out>, 
    f=<optimized out>, throwflag=<optimized out>) at Python/ceval.c:3516
#8  0x00005555556864f5 in _PyEval_EvalFrame (throwflag=0, f=0x7ffff6f20c40, 
    tstate=0x555555b2c350) at ./Include/internal/pycore_ceval.h:40
#9  _PyEval_EvalCode (qualname=0x7ffff6e860f0, name=0x7ffff6e860f0, closure=0x0, 
    kwdefs=0x0, defcount=0, defs=0x0, kwstep=2, kwcount=0, kwargs=0x0, 
    kwnames=0x0, argcount=0, args=0x0, locals=0x0, globals=0x555555b2c350, 
    _co=0x7ffff6ee6d40, tstate=0x555555b2c350) at Python/ceval.c:4376
#10 _PyEval_EvalCodeWithName (qualname=0x0, name=0x0, closure=0x0, kwdefs=0x0, 
    defcount=0, defs=0x0, kwstep=2, kwcount=0, kwargs=0x0, kwnames=0x0, 
    argcount=0, args=0x0, locals=locals@entry=0x0, 
    globals=globals@entry=0x555555b2c350, _co=0x7ffff6ee6d40, 
    _co@entry=0x7ffff6f20da0) at Python/ceval.c:4408
#11 PyEval_EvalCodeEx (closure=0x0, kwdefs=0x0, defcount=0, defs=0x0, kwcount=0, 
    kws=0x0, argcount=0, args=0x0, locals=locals@entry=0x0, 
    globals=globals@entry=0x555555b2c350, _co=0x7ffff6ee6d40, 
    _co@entry=0x7ffff6f20da0) at Python/ceval.c:4424
---Type <return> to continue, or q <return> to quit---
#12 PyEval_EvalCode (co=co@entry=0x7ffff6ee6d40, 
    globals=globals@entry=0x7ffff6f4e440, locals=locals@entry=0x7ffff6f4e440)
    at Python/ceval.c:857
#13 0x00005555556d69c6 in run_eval_code_obj (locals=0x7ffff6f4e440, 
    globals=0x7ffff6f4e440, co=0x7ffff6ee6d40, tstate=0x555555b2c350)
    at Python/pythonrun.c:1124
#14 run_mod (arena=0x7ffff6fa1910, flags=0x7fffffffe128, locals=0x7ffff6f4e440, 
    globals=0x7ffff6f4e440, filename=0x7ffff6e815d0, mod=<optimized out>)
    at Python/pythonrun.c:1145
#15 PyRun_FileExFlags (fp=fp@entry=0x555555b89b40, 
    filename_str=filename_str@entry=0x7ffff6f5a050 "/root/cpython/../backups/bpo41321.py", start=start@entry=257, globals=globals@entry=0x7ffff6f4e440, 
    locals=locals@entry=0x7ffff6f4e440, closeit=closeit@entry=1, 
    flags=0x7fffffffe128) at Python/pythonrun.c:1062
#16 0x00005555556d6b9d in PyRun_SimpleFileExFlags (fp=fp@entry=0x555555b89b40, 
    filename=<optimized out>, closeit=closeit@entry=1, 
    flags=flags@entry=0x7fffffffe128) at Python/pythonrun.c:397
#17 0x00005555556d70e3 in PyRun_AnyFileExFlags (fp=fp@entry=0x555555b89b40, 
    filename=<optimized out>, closeit=closeit@entry=1, 
    flags=flags@entry=0x7fffffffe128) at Python/pythonrun.c:80
#18 0x00005555555b52a0 in pymain_run_file (cf=0x7fffffffe128, 
    config=0x555555b28db0) at Modules/main.c:369
#19 pymain_run_python (exitcode=0x7fffffffe11c) at Modules/main.c:594
#20 Py_RunMain () at Modules/main.c:673
#21 0x00005555555b57d6 in pymain_main (args=0x7fffffffe210) at Modules/main.c:703
#22 Py_BytesMain (argc=<optimized out>, argv=<optimized out>)
    at Modules/main.c:727
#23 0x00007ffff7041b97 in __libc_start_main (main=0x5555555aa2b0 <main>, argc=2, 
    argv=0x7fffffffe368, init=<optimized out>, fini=<optimized out>, 
    rtld_fini=<optimized out>, stack_end=0x7fffffffe358)
    at ../csu/libc-start.c:310
#24 0x00005555555b446a in _start ()