Import dll procedure exception

[f1engineer]

Dear Sirs
I have a problem to importing procedure from Visual C++ 6.0 dynamic link library:

1. In my Delphi project i do define the imported function as:

StartLoggingrocedure(AData: byte);cdecl{$IFDEF WIN32} stdcall {$ENDIF};

2. StartLogging:=GetProcAddress(Handle, 'StartLogging');
Handle - is the handle to the dll that I previously load.

3. When a valid procedure pointer came, I sucessfuly call the function and pass all the requared parameters. But just in the end of procedure where I call StartLogging an exception appear: 'Access violation at address 0012F6FF. Write of address 8C13390D'.

I resolved the problem by inserting an assembler code in the procedure but this is not enaugh safely.

Can anyone help me?
Regards Kamen

 

[earthandfire]

Don't forget that if any of the parameters are strings they are normally long pointers to an ASCIIZ (ie a PChar)

Hope this helps.

 

[f1engineer]

In this case there is only one input parameter and it is unsigned char of C++ part that the imported function is implemented and when I call this function I pass variable of type byte that is equivalent of unsigned char

C++ code:
extern "C"__declspec(dllexport)void StartLogging(unsigned char AValue)
{
//body
}

Delphi client:
procedure TForm1.MyDelphiProcedure(TSender: TObject);
var
param:byte;
......
begin
StartLogging:=GetProcAddress(Handle, 'StartLogging');

param:=5;
StartLogging(param);//successful
.......
.......
end;//successful

in project main fail there is:

program Project2;

uses
Forms,
PROJECT1 in 'PROJECT1.pas' {Form1};

{$R *.res}
begin
Application.Initialize;
Application.CreateForm(TForm1, Form1);
Application.Run;
end.//EXCEPTION - 'Access violation at address 0012F6FF. Write of address 8C13390D'