Creating user defined function for firebird 2.5 with c++builder 2010

Question

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?

Answer 1

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!