[Bug gdb/34047] gdb Fatal signal: Bus error | SIGBUS (Misaligned address error)

https://sourceware.org/bugzilla/show_bug.cgi?id=34047

--- Comment #13 from Simon Marchi <simark at simark dot ca> ---
Ok, I built my own gdb inside the container and got a nice backtrace (see
below).  I am not sure we're looking at the same thing as your original report
though.

The problem looks like:

 - inf 1 vforks, creating inf 2, and we want to detach from inf 1
 - handle_vfork_child_exec_or_exit purposefully sets inf 2's pspace to nullptr
while detaching inf 1, as explained here:

  
https://gitlab.com/gnutools/binutils-gdb/-/blob/cd05beed352d69e282e9fae6f69bfec48a8faedf/gdb/infrun.c#L1118
 - while detaching, the inferior_disappeared observer gets called, which sends
the Python "inferior exited" event
 - the Python code calls "info program"
 - the handler for "info program" obtains a thread using get_previous_thread(),
which returns a thread from inf 2
 - it tries to switch to that thread, which tries to set that inferior's pspace
as the current program space, and because it is nullptr the assert triggers



#8  0x000055f94ff03d87 in internal_error_loc (file=0x55f95000acbf
"/binutils-gdb/gdb/progspace.c", line=248, fmt=0x55f95000ac28 "%s: Assertion
`%s' failed.") at /binutils-gdb/gdbsupport/errors.cc:57
#9  0x000055f94fa02271 in set_current_program_space (pspace=0x0) at
/binutils-gdb/gdb/progspace.c:248
#10 0x000055f94fc4256b in switch_to_thread_no_regs (thread=0x55f951a50350) at
/binutils-gdb/gdb/thread.c:1464
#11 0x000055f94fc426ee in switch_to_thread (thr=0x55f951a50350) at
/binutils-gdb/gdb/thread.c:1496
#12 0x000055f94f895b66 in info_program_command (args=0x0, from_tty=0) at
/binutils-gdb/gdb/infcmd.c:2102
#13 0x000055f94f5b7dbf in do_simple_func (args=0x0, from_tty=0,
c=0x55f9509b1090) at /binutils-gdb/gdb/cli/cli-decode.c:86
#14 0x000055f94f5be3dd in cmd_func (cmd=0x55f9509b1090, args=0x0, from_tty=0)
at /binutils-gdb/gdb/cli/cli-decode.c:2810
#15 0x000055f94fc4cf64 in execute_command (p=0x7ffdeeade96c "", from_tty=0) at
/binutils-gdb/gdb/top.c:632
#16 0x000055f94f5ce2ea in execute_control_command_1 (cmd=0x55f95150e650,
from_tty=0) at /binutils-gdb/gdb/cli/cli-script.c:530
#17 0x000055f94f5cea1e in execute_control_command (cmd=0x55f95150e650,
from_tty=0) at /binutils-gdb/gdb/cli/cli-script.c:706
#18 0x000055f94f5cdd5d in execute_control_commands (cmdlines=0x55f95150e650,
from_tty=0) at /binutils-gdb/gdb/cli/cli-script.c:412
#19 0x000055f94f5cde42 in operator() (__closure=0x7ffdeeadec40) at
/binutils-gdb/gdb/cli/cli-script.c:433
#20 0x000055f94f5d232c in std::__invoke_impl<void,
execute_control_commands_to_string(command_line*, int,
bool)::<lambda()>&>(std::__invoke_other, struct {...} &) (__f=...) at
/usr/include/c++/13/bits/invoke.h:61
#21 0x000055f94f5d2213 in std::__invoke_r<void,
execute_control_commands_to_string(command_line*, int,
bool)::<lambda()>&>(struct {...} &) (__fn=...) at
/usr/include/c++/13/bits/invoke.h:111
#22 0x000055f94f5d20d3 in std::_Function_handler<void(),
execute_control_commands_to_string(command_line*, int, bool)::<lambda()>
>::_M_invoke(const std::_Any_data &) (__functor=...) at
/usr/include/c++/13/bits/std_function.h:290
#23 0x000055f94f5daa30 in std::function<void()>::operator()
(this=0x7ffdeeadec40) at /usr/include/c++/13/bits/std_function.h:591
#24 0x000055f94fc4d3ba in execute_fn_to_ui_file (file=0x7ffdeeadec60, fn=...)
at /binutils-gdb/gdb/top.c:684
#25 0x000055f94fc4d5fa in execute_fn_to_string (res="", fn=..., term_out=true)
at /binutils-gdb/gdb/top.c:697
#26 0x000055f94f5cdeb9 in
execute_control_commands_to_string[abi:cxx11](command_line*, int, bool)
(commands=0x55f95150e650, from_tty=0, term_out=true) at
/binutils-gdb/gdb/cli/cli-script.c:431
#27 0x000055f94faa2d2c in execute_gdb_command (self=0x7f5e95de1d00,
args=0x7f5e8c2f2860, kw=0x7f5e8c31a700) at
/binutils-gdb/gdb/python/python.c:780
#28 0x00007f5ea24454b8 in cfunction_call (func=0x7f5e95e00a90,
args=0x7f5e8c2f2860, kwargs=0x7f5e8c31a700) at ../Objects/methodobject.c:537
#29 0x00007f5ea23e87df in _PyObject_MakeTpCall (tstate=0x7f5ea2b09668
<_PyRuntime+459656>, callable=callable@entry=0x7f5e95e00a90,
args=args@entry=0x7f5e95ed73c8, nargs=<optimized out>, keywords=0x7f5e94f43b80)
at ../Objects/call.c:240
#30 0x00007f5ea23e8b77 in _PyObject_VectorcallTstate (kwnames=<optimized out>,
nargsf=<optimized out>, args=0x7f5e95ed73c8, callable=0x7f5e95e00a90,
tstate=<optimized out>) at ../Include/internal/pycore_call.h:90
#31 0x00007f5ea23835ee in _PyEval_EvalFrameDefault (tstate=<optimized out>,
frame=<optimized out>, throwflag=<optimized out>) at Python/bytecodes.c:2706
#32 0x00007f5ea267d2bd in _PyObject_VectorcallTstate (kwnames=0x0, nargsf=2,
args=0x7ffdeeadf120, callable=0x7f5e94c83920, tstate=0x7f5ea2b09668
<_PyRuntime+459656>) at ../Include/internal/pycore_call.h:92
#33 partial_vectorcall (pto=0x7f5e943c9da0, args=<optimized out>,
nargsf=<optimized out>, kwnames=0x0) at ../Modules/_functoolsmodule.c:267
#34 0x00007f5ea237fdec in _PyEval_EvalFrameDefault (tstate=<optimized out>,
frame=<optimized out>, throwflag=<optimized out>) at Python/bytecodes.c:3254
#35 0x00007f5ea23e8d9e in _PyObject_VectorcallTstate (kwnames=0x0, nargsf=1,
args=0x7ffdeeadf350, callable=0x7f5e943ec9a0, tstate=0x7f5ea2b09668
<_PyRuntime+459656>) at ../Include/internal/pycore_call.h:92
#36 object_vacall (tstate=0x7f5ea2b09668 <_PyRuntime+459656>,
base=base@entry=0x0, callable=callable@entry=0x7f5e943ec9a0,
vargs=vargs@entry=0x7ffdeeadf3c8) at ../Objects/call.c:850
#37 0x00007f5ea23e92de in PyObject_CallFunctionObjArgs
(callable=0x7f5e943ec9a0) at ../Objects/call.c:957
#38 0x000055f94fa2d93e in evpy_emit_event (event=0x7f5e8c2536b0,
registry=0x7f5e95b8ec30) at /binutils-gdb/gdb/python/py-event.c:86
#39 0x000055f94fa2ec2a in emit_exited_event (exit_code=0x0, inf=0x55f9509694e0)
at /binutils-gdb/gdb/python/py-exitedevent.c:62
#40 0x000055f94fa3bbe5 in python_inferior_exit (inf=0x55f9509694e0) at
/binutils-gdb/gdb/python/py-inferior.c:162
#41 0x000055f94f4603a8 in std::__invoke_impl<void, void (*&)(inferior*),
inferior*> (__f=@0x55f950a76810: 0x55f94fa3bb55
<python_inferior_exit(inferior*)>) at /usr/include/c++/13/bits/invoke.h:61
#42 0x000055f94f45b10b in std::__invoke_r<void, void (*&)(inferior*),
inferior*> (__fn=@0x55f950a76810: 0x55f94fa3bb55
<python_inferior_exit(inferior*)>) at /usr/include/c++/13/bits/invoke.h:111
#43 0x000055f94f4566f0 in std::_Function_handler<void(inferior*), void
(*)(inferior*)>::_M_invoke (__functor=..., __args#0=@0x7ffdeeadf660:
0x55f9509694e0) at /usr/include/c++/13/bits/std_function.h:290
#44 0x000055f94f630311 in std::function<void(inferior*)>::operator()
(this=0x55f950a76810, __args#0=0x55f9509694e0) at
/usr/include/c++/13/bits/std_function.h:591
#45 0x000055f94f62d55e in gdb::observers::observable<inferior*>::notify
(this=0x55f9504f55e0 <gdb::observers::inferior_exit>, args#0=0x55f9509694e0) at
/binutils-gdb/gdb/../gdbsupport/observable.h:166
#46 0x000055f94f89d927 in notify_inferior_disappeared (inf=0x55f9509694e0) at
/binutils-gdb/gdb/inferior.c:305
#47 0x000055f94f89d961 in exit_inferior (inf=0x55f9509694e0) at
/binutils-gdb/gdb/inferior.c:315
#48 0x000055f94fc1b075 in generic_mourn_inferior () at
/binutils-gdb/gdb/target.c:3666
#49 0x000055f94fb0537f in remote_target::mourn_inferior (this=0x55f95187bde0)
at /binutils-gdb/gdb/remote.c:11228
#50 0x000055f94fc190aa in target_mourn_inferior (ptid=...) at
/binutils-gdb/gdb/target.c:2771
#51 0x000055f94faf842b in remote_target::remote_detach_1 (this=0x55f95187bde0,
inf=0x55f9509694e0, from_tty=0) at /binutils-gdb/gdb/remote.c:6957
#52 0x000055f94faf8513 in remote_target::detach (this=0x55f95187bde0,
inf=0x55f9509694e0, from_tty=0) at /binutils-gdb/gdb/remote.c:6972
#53 0x000055f94fc1830f in target_detach (inf=0x55f9509694e0, from_tty=0) at
/binutils-gdb/gdb/target.c:2568
#54 0x000055f94f8a9e57 in handle_vfork_child_exec_or_exit (exec=1) at
/binutils-gdb/gdb/infrun.c:1140
#55 0x000055f94f8b96d5 in handle_inferior_event (ecs=0x7ffdeeadff30) at
/binutils-gdb/gdb/infrun.c:6630
#56 0x000055f94f8b414d in fetch_inferior_event () at
/binutils-gdb/gdb/infrun.c:4756
#57 0x000055f94f885a69 in inferior_event_handler (event_type=INF_REG_EVENT) at
/binutils-gdb/gdb/inf-loop.c:42
#58 0x000055f94fb14070 in remote_async_serial_handler (scb=0x55f951882470,
context=0x55f95187c148) at /binutils-gdb/gdb/remote.c:15975
#59 0x000055f94fb49f7e in run_async_handler_and_reschedule (scb=0x55f951882470)
at /binutils-gdb/gdb/ser-base.c:138
#60 0x000055f94fb4a065 in fd_event (error=0, context=0x55f951882470) at
/binutils-gdb/gdb/ser-base.c:189
#61 0x000055f94ff04e93 in handle_file_event (file_ptr=0x55f951b0d520,
ready_mask=1) at /binutils-gdb/gdbsupport/event-loop.cc:551
#62 0x000055f94ff05514 in gdb_wait_for_event (block=1) at
/binutils-gdb/gdbsupport/event-loop.cc:672
#63 0x000055f94ff042d2 in gdb_do_one_event (mstimeout=-1) at
/binutils-gdb/gdbsupport/event-loop.cc:263
#64 0x000055f94f5c5e73 in interp::do_one_event (this=0x55f950b6f170,
mstimeout=-1) at /binutils-gdb/gdb/interps.h:90
#65 0x000055f94f95a784 in start_event_loop () at /binutils-gdb/gdb/main.c:400
#66 0x000055f94f95a974 in captured_command_loop () at
/binutils-gdb/gdb/main.c:465
#67 0x000055f94f95c656 in captured_main (context=0x7ffdeeae0380) at
/binutils-gdb/gdb/main.c:1373
#68 0x000055f94f95c700 in gdb_main (args=0x7ffdeeae0380) at
/binutils-gdb/gdb/main.c:1392
#69 0x000055f94f3eb39f in main (argc=5, argv=0x7ffdeeae04c8) at
/binutils-gdb/gdb/gdb.c:38

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