Pbm in Dll (pls Francois)

Question

Hi,
I created a test.dll using Microsoft visual c++ by following steps.
I opened a new project by
New--Project--win32 dynamic link library
I added a new src file test.c to project and edited it as:
int caps()
int *src=0x417;
if (*src==64)
return 1;
else
return 0;
I added a header file test.h and added
int caps()
I compiled the test.c with no errors.Then I built test.dll by pressing make test.dll.
Now If I view test.dll with a utility called DLLEXP(Utility to see func present in DLL),
Caps is not appearing in it.Thats y forms is also giving an error like caps is not found in test.dll.
I'm totally confused.
What is wrong in my process?
Pls its urgent...I've to use this dll in ORA_FFI package.
Adios..

Answer 1

Here is a Metalink sample
The memory for the char pointer must be globally allocated using a GlobalAlloc
(with the GMEM_FIXED flag) such that the memory is not resident on the stack.
The problem with allocating memory on the stack for the pointer is that this
memory block will be freed when the function exits and the returned pointer
will become invalid.
Here is a complete example showing a successful implementation of this
functionality. Although the following code demonstrates a 16bit
implementation, the same holds true for 32bit implementations.
-- This calling trigger's code                                --
declare
  -- Parameters
  parm1 VARCHAR2(128) := 'X';
  -- Return value
  rt VARCHAR2(512) := 'Hello Folks';
begin
  rt := MyLib.MyFunc1( parm1 );
  Message(rt);
end;
-- This wrapper package's header                             --
PACKAGE MyLib IS
  FUNCTION MyFunc1( parm1 IN OUT VARCHAR2 )
                    RETURN VARCHAR2;  
END;
-- This wrapper package's body                               --
PACKAGE BODY MyLib IS
  lib_hndl  ora_ffi.libHandleType;  
  func_hndl ora_ffi.funcHandleType;  
  FUNCTION i_MyFunc1( func_hndl IN ora_ffi.funcHandleType,  
                      parm1 IN OUT VARCHAR2 )
                      RETURN VARCHAR2;  
  PRAGMA INTERFACE(C,i_MyFunc1,11265);  
  FUNCTION MyFunc1( parm1 IN OUT VARCHAR2 )
                      RETURN VARCHAR2 
  IS   
    parm1_l  VARCHAR2 := parm1;
    rc       VARCHAR2(512);
  BEGIN   
    rc  := i_MyFunc1(func_hndl, parm1_l);
    RETURN (rc);  
  END ;  
BEGIN   
  lib_hndl := ora_ffi.load_library(NULL,'DLL16.DLL');  
  func_hndl :=
ora_ffi.register_function(lib_hndl,'PASCAL_TEST',ora_ffi.PASCAL_STD);
  ora_ffi.register_parameter(func_hndl,ORA_FFI.C_CHAR_PTR);
  ora_ffi.register_return(func_hndl,ORA_FFI.C_CHAR_PTR);
END;
-- This DLL's DEF file                                       --
LIBRARY      DLL16
EXETYPE      WINDOWS
CODE         PRELOAD MOVEABLE DISCARDABLE
DATA         PRELOAD SINGLE
HEAPSIZE     4096
EXPORTS
             WEP PRIVATE
             Pascal_Test  @1
-- This DLL's CPP file                                       --
#include <windows.h>
#include <string.h>
int CALLBACK LibMain(HANDLE hInstance, WORD wDataSeg, WORD wHeapSize, LPSTR
lpszCmdLine)
        if (wHeapSize > 0 )
                UnlockData (0);  // Unlocks the library's data segment
        return 1;
char* FAR PASCAL __export Pascal_Test (char* xyz)  
    HGLOBAL hgl;
    char FAR* abc;
    hgl = GlobalAlloc(GPTR, 256);
    abc = (char*)GlobalLock(hgl);
    strcpy(abc,"Hello World");
        GlobalUnlock(hgl);
        MessageBox(NULL,abc,"Pascal",MB_OK);
    return abc;
}Hope this help
Francois