Submitted by: christophe derenne (cdr60530)

With a fresh firebird-superserver 2.5.7 installation
create a new database
for example
/var/lib/firebird/data/test.fdb
with sqldialect 3, charset UTF-8

crate a very simple table :
create table tbtest (idtest integer not null);

Make some row (for exemple 10 rows from idtest=1 to idtest=10)

insert into tbtest (idtest)
values
(1);
insert into tbtest (idtest)
values
(2);
insert into tbtest (idtest)
values
(3);
insert into tbtest (idtest)
values
(4);
insert into tbtest (idtest)
values
(5);
insert into tbtest (idtest)
values
(6);
insert into tbtest (idtest)
values
(7);
insert into tbtest (idtest)
values
(8);
insert into tbtest (idtest)
values
(9);
insert into tbtest (idtest)
values
(10);

register a fbudf function :
fo exemple :
declare external function ADDDAY
timestamp, int
returns timestamp
entry_point 'addday' module_name 'fbudf';

declare external function ADDDAY2
timestamp, int
returns timestamp
entry_point 'addDay' module_name 'fbudf';

Use thoses functions

select 100*a.idtest+10*b.idtest+c.idtest, addDay(cast('2001-01-01' as timestamp),100*a.idtest+10*b.idtest+c.idtest) from tbtest a
join tbtest b on 1=1 join tbtest c on 1=1;

result :
invalid request BLR at offset 91
function ADDDAY is not defined
module name or entrypoint could not be found

select 100*a.idtest+10*b.idtest+c.idtest, addDay2(cast('2001-01-01' as timestamp),100*a.idtest+10*b.idtest+c.idtest) from tbtest a
join tbtest b on 1=1 join tbtest c on 1=1;

Result ok :

But both functions is working from FB1.5 to FB2.5

It seems that
the entry point module name has become case sensitive in FB2.5.7

For old database with stored procedure or view depends on udf function, we cannot drop/create to correct the entry point 's caractere case.
Except create empty database with correct metadata and then insert data.