Submitted by: @romansimakov

Run
{{{
create database '/tmp/gen.fdb'^
execute block
as
begin
in autonomous transaction do
begin
execute statement 'create sequence s';
execute statement 'comment on sequence s is ''1'' ';
end
end^
}}}

to get crash with stack

{{{
(gdb) bt
#⁠0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:58
#⁠1 0x00007ffff633c37a in __GI_abort () at abort.c:89
#⁠2 0x00007ffff768f835 in Jrd::jrd_tra::getUndoSpace (this=0x7ffff069ad48) at ../src/jrd/../jrd/tra.h:257
#⁠3 0x00007ffff768fc6a in Jrd::UndoItem::UndoItem (this=0x7fffffffada0, transaction=0x7ffff069ad48, recordNumber=...,
record=0x7ffff067bf98, recordFlags=0 '\000') at ../src/jrd/../jrd/tra.h:493
#⁠4 0x00007ffff768ee0d in verb_post (tdbb=0x7fffffffbc60, transaction=0x7ffff069ad48, rpb=0x7ffff067b078, old_data=0x7ffff067bf98,
same_tx=false, new_ver=false) at ../src/jrd/vio.cpp:5475
#⁠5 0x00007ffff7688a2e in VIO_modify (tdbb=0x7fffffffbc60, org_rpb=0x7ffff067b078, new_rpb=0x7ffff067b118,
transaction=0x7ffff069ad48) at ../src/jrd/vio.cpp:2497
#⁠6 0x00007ffff75a592b in modify (tdbb=0x7fffffffbc60, node=0x7ffff0692d68, which_trig=0) at ../src/jrd/exe.cpp:3008
#⁠7 0x00007ffff75a44d4 in EXE_looper (tdbb=0x7fffffffbc60, request=0x7ffff067ab18, in_node=0x7ffff0692df0) at ../src/jrd/exe.cpp:2564
#⁠8 0x00007ffff75a5449 in looper_seh (tdbb=0x7fffffffbc60, request=0x7ffff067ab18, node=0x7ffff0692df0) at ../src/jrd/exe.cpp:2917
#⁠9 0x00007ffff75a07f4 in execute_looper (tdbb=0x7fffffffbc60, request=0x7ffff067ab18, transaction=0x7ffff069ad48,
node=0x7ffff0692df0, next_state=Jrd::jrd_req::req_proceed) at ../src/jrd/exe.cpp:1369
#⁠10 0x00007ffff759f94e in EXE_send (tdbb=0x7fffffffbc60, request=0x7ffff067ab18, msg=2, length=10, buffer=0x7fffffffb4c0 "")
at ../src/jrd/exe.cpp:971
#⁠11 0x00007ffff74af2ec in DYN_modify_generator (gbl=0x7fffffffb5d0, ptr=0x7fffffffb5e8) at ../temp/std/jrd/dyn_mod.cpp:1415
#⁠12 0x00007ffff748a8a1 in DYN_execute (gbl=0x7fffffffb5d0, ptr=0x7fffffffb5e8, relation_name=0x0, field_name=0x0, trigger_name=0x0,
function_name=0x0, procedure_name=0x0) at ../temp/std/jrd/dyn.cpp:642
#⁠13 0x00007ffff7489d19 in DYN_ddl (transaction=0x7ffff069ad48, length=11, ddl=0x7ffff068daf8 "\001\342\001")
at ../temp/std/jrd/dyn.cpp:290
#⁠14 0x00007ffff75ea3ea in JRD_ddl (tdbb=0x7fffffffbc60, transaction=0x7ffff069ad48, ddl_length=11, ddl=0x7ffff068daf8 "\001\342\001")
at ../src/jrd/jrd.cpp:6946
#⁠15 0x00007ffff76ddd06 in DDL_execute (request=0x7ffff068da90) at ../src/dsql/ddl.cpp:383
#⁠16 0x00007ffff76f8474 in execute_request (tdbb=0x7fffffffbc60, request=0x7ffff068da90, tra_handle=0x7fffffffbd98, in_blr_length=7,
in_blr=0x7ffff7f9eb38 "\005\002\004", in_msg_length=0,
in_msg=0x7ffff7f9ea80 "\355\253\355\376\355\253\355\376\355\253\355\376\355\253\355\376", out_blr_length=7,
out_blr=0x7ffff7f9eb68 "\005\002\004", out_msg_length=0,
out_msg=0x7ffff7f9eab0 "\355\253\355\376\355\253\355\376\355\253\355\376\355\253\355\376", singleton=false)
at ../src/dsql/dsql.cpp:1228
...
}}}