create or alter procedure SET_CALLER_NAME
as
declare variable NM varchar(100);
declare variable TR integer;
begin
  TR = current_transaction;
  in autonomous transaction
  do select cs.MON$OBJECT_NAME
     from MON$CALL_STACK cs
     where exists(select *
            from MON$CALL_STACK cs1
            join MON$STATEMENTS s on s.MON$STATEMENT_ID = cs1.MON$STATEMENT_ID and s.MON$STATE = 1
            where s.MON$TRANSACTION_ID = :TR
              and upper(cs1.MON$OBJECT_NAME) = 'SET_CALLER_NAME'
              and cs1.MON$CALLER_ID = cs.MON$CALL_ID)
     into :NM;
  RDB$SET_CONTEXT('USER_TRANSACTION', 'CALLER_NAME', :NM);
end

create or alter procedure TEST_A
returns (NM varchar(100))
as
begin
  execute procedure SET_CALLER_NAME;
  NM = RDB$GET_CONTEXT('USER_TRANSACTION', 'CALLER_NAME');
  RDB$SET_CONTEXT('USER_TRANSACTION', 'CALLER_NAME', null);
  suspend;
end

create or alter procedure TEST_B
returns (NM varchar(100))
as
begin
  execute procedure SET_CALLER_NAME;
  NM = RDB$GET_CONTEXT('USER_TRANSACTION', 'CALLER_NAME');
  RDB$SET_CONTEXT('USER_TRANSACTION', 'CALLER_NAME', null);
  suspend;
end

select TEST_B.NM, TEST_A.NM
from TEST_B
join TEST_A on 0 = 0