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I tried to create a simple user defined function (UDF) for Firebird 2.5 with C++ Builder 2010 but I don't manage to get it to work in Firebird.

  1. Creating a DLL project with default setting in C++ Builder 2010.

  2. Adding a unit with my example UDF including "ibase.h" and "ib_util.h":

    extern "C" __declspec(dllexport) int __stdcall MYFUNC ( int i )  
{  
     int result = 2 * i;  
     return result;  
}

  3. Building the DLL FBUDFMBD.dll in path C:\Program Files (x86)\Firebird\Firebird_2_5\UDF

  4. Registering my UDF via IBExpert in a sample db with 

    DECLARE EXTERNAL FUNCTION F_MYFUNC  
INTEGER  
RETURNS INTEGER 
ENTRY_POINT 'MYFUNC' MODULE_NAME 'FBUDFMBD';

  5. Calling the UDF with 

    select F_MYFUNC( 3 ) from RDB$DATABASE;

    results in error message

    Invalid token.  
invalid request BLR at offset 36.  
function F_MYFUNC is not defined.  
module name or entrypoint could not be found.

With the tool GExperts - PE Information I can see my UDF as DLL-Export MYFUNC ordinal $1 and entry point $1538.

What I am doing wrong, Firebird can't register my DLL and its UDF correctly?

Is there anything in my DLL project to change regarding to default compiler options?

Mark Rotteveel
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Bernd E.
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  • In my experience Firebird UDF question - usually - don't get a lot of answers here; you might want to consider asking your question on the Firebird-support mailinglist as well. – Mark Rotteveel Jul 21 '16 at 17:21
  • I'm not 100% sure, but I believe you need to remove the `extern "C" __declspec(dllexport)`, look for an example at https://github.com/FirebirdSQL/firebird/blob/8905e15435116bfac3abb30ae476d4812d1fe04b/src/extlib/ib_udf.cpp – Mark Rotteveel Jul 21 '16 at 17:39

2 Answers2

2

In Delphi, you can write cdecl and not stdcall

i.e

function ExisteBase(const aBase:PChar):Integer; cdecl;

Not

function ExisteBase(const aBase:PChar):Integer; stdcall;

Maybe on C++ __cdecl

I hope I helped in some

manlio
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Mario Ruiz
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2

Thanks a lot! I got it by your help.

top 2: Corrected C++-Code is: 

extern "C" __declspec(dllexport) int MYFUNC ( int * val )
{
   int result = 2 * *val;
   return result;
}

Pay attention to reference call of the input parameter.

top 4: Register the UDF in a firebird 2.5 db by 

DECLARE EXTERNAL FUNCTION F_MYFUNC
INTEGER
RETURNS INTEGER BY VALUE
ENTRY_POINT '_MYFUNC' MODULE_NAME 'FBUDFMBD';

Pay attention to the leading underscore at the function name!

top 5: select F_MYFUNC( 3 ) from RDB$DATABASE; works really fine!

Bernd E.
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