Oracle External Procedures with Delphi DLL - oracle

Question

I have been trying to configure the "External Procedures" Feature for my Oracle Database 18c on Windows 10.
The documentation claims, to set up this feature, it is basically just necessary to set the environment values in extrproc.ora - which in my case is just one line of: SET EXTPROC_DLLS=ANY (for testing purposes).
I have created a DLL to test my configuration by using Delphi with the following code:
library testdll;
function Sum(x, y: Integer): Integer; stdcall;
begin
Result := x + y;
end;
function Subtract(x, y: Integer): Integer; stdcall;
begin
Result := x - y;
end;
procedure TEST; stdcall;
begin
end;
exports
TEST,
Sum,
Subtract;
begin
end.
So my first question would be: Do I need to compile the DLLs as x64 or as x86? Also, is the calling convention stdcall compatible with Oracle 18c?
Furthermore I have created a Library Alias in my database using:
CREATE OR REPLACE LIBRARY MySchema.TESTDLL AS 'C:\testdll.dll'
The external procedure has been published by
create or replace PROCEDURE TESTPROCEDURE
AS LANGUAGE C
NAME "TEST"
LIBRARY TESTDLL;
Now that I have everything setup on the database, I tried calling the procedure:
begin
TESTPROCEDURE();
end;
But when I tried calling it, I get the following Error:
ORA-06520: PL/SQL: Fehler beim Laden der externen Library
ORA-06522: Unable to load DLL
ORA-06512: in "MySchema.TESTPROCEDURE", Zeile 1
ORA-06512: in Zeile 2
06520. 00000 - "PL/SQL: Error loading external library"
*Cause: An error was detected by PL/SQL trying to load the external
library dynamically.
*Action: Check the stacked error (if any) for more details.
Info:
The database spawns the extproc.exe properly, after I call the procedure
How do I get this work properly and are Delphi DLLs even compatible?
This is my listener.ora file:
# listener.ora Network Configuration File: C:\app\oracle\product\18.0.0\dbhomeXE\NETWORK\ADMIN\listener.ora
# Generated by Oracle configuration tools.
DEFAULT_SERVICE_LISTENER = XE
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = CLRExtProc)
(ORACLE_HOME = C:\app\oracle\product\18.0.0\dbhomeXE)
(PROGRAM = extproc)
(ENVS = "EXTPROC_DLLS=ONLY:C:\app\oracle\product\18.0.0\dbhomeXE\bin\oraclr18.dll")
)
)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
)
)
And this is my tnsnames.ora file:
# tnsnames.ora Network Configuration File: C:\app\oracle\product\18.0.0\dbhomeXE\NETWORK\ADMIN\tnsnames.ora
# Generated by Oracle configuration tools.
XE =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = XE)
)
)
LISTENER_XE =
(ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))
ORACLR_CONNECTION_DATA =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
)
(CONNECT_DATA =
(SID = CLRExtProc)
(PRESENTATION = RO)
)
)
Any ideas what could be wrong with my configuration?
Edit:
This is the .c dll example code from the database:
/*
** Copyright (c) 1997 by Oracle Corporation
**
** NAME
** EXTERN.C
**
** DESCRIPTION
** Sample Windows NT External Procedure: find_max
**
*/
#include <windows.h>
#define NullValue -1
/*
This function simply returns the returns the larger of x and y.
*/
long __declspec(dllexport) find_max(long x,
short x_indicator,
long y,
short y_indicator,
short *ret_indicator)
{
/* It can be tricky to debug DLL's that are being called by a process
that is spawned only when needed, as in this case.
Therefore try using the DebugBreak(); command.
This will start your debugger. Uncomment the following line and
you can step right into your code.
*/
/* DebugBreak(); */
/* first check to see if you have any nulls */
/* Just return a null if either x or y is null */
if ( x_indicator==NullValue || y_indicator==NullValue) {
*ret_indicator = NullValue;
return(0);
} else {
*ret_indicator = 0; /* Signify that return value is not null */
if (x >= y) return x;
else return y;
}
}
And this is the make.bat file:
REM USAGE: just type MAKE
if (%PROCESSOR_ARCHITECTURE%)==(IA64) goto win64_ia64
if (%PROCESSOR_ARCHITECTURE%)==(AMD64) goto win64_amd64
cl -I. /LD -Zi extern.c /link msvcrt.lib /nod:libcmt /DLL
goto fi
:win64_ia64
cl /DWIN64 /D_WIN64 /DSS_64BIT_SERVER /D_IA64_=1 -I. /LD -Zi extern.c /link msvcrt.lib /nod:libcmt /DLL
goto fi
:win64_amd64
cl /GS- /DWIN64 /D_WIN64 /DSS_64BIT_SERVER /D_AMD64_=1 -I. /LD -Zi extern.c /link msvcrt.lib /MACHINE:AMD64 /nod:libcmt /DLL
goto fi
:fi

Answer 1

Based on the information provided, I can see the following:
The C example is compiled as a 64 bit DLL.
The C example does not specify a calling convention and so uses the default which is cdecl.
The example C functions accept 5 arguments, but your functions accept only 2.