Can my dll be used in another programming language
lazarus / 67-Windows

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vkhoa · 2015-06-18 06:54

I wrote a library like this
Code: [Select]library library_delegate;
uses Classes, SysUtils;
type commandevent=procedure (text:string);
var ocommand:commandevent;
procedure create(cmd:commandevent);stdcall;
begin
  ocommand:=cmd;
end;

procedure writetext(text:string);stdcall;
begin
  if assigned(ocommand) then
     ocommand(text);
end;
exports create,writetext;
begin
end.then compiled it to "library_delegate.dll"
after that I wrote a program
Code: [Select]program use_library_delegate;
uses Classes, SysUtils;
type commandevent=procedure (text:string);
procedure create(cmd:commandevent);stdcall;external
'library_delegate';
procedure writetext(text:string);stdcall;external 'library_delegate';
procedure writeatext(text:string);
begin
  writeln(text);
end;
var i:integer;
begin
  create(@writeatext);
  for i:=1 to 100 do
      writetext('Text line '+inttostr(i));
  readln;
end.the program run as I expected, it wrote 100 text line to the
console
I want to know if this dll could be used in visual basic or C(or other
windows programming language). And I am curious to know how simple it
is to use the dll's function in those language (especially at passing
the procedure type parameter in the "create" procedure), can you give
me any examples.
another question, can we assign or read the "ocommand" directly from
the program?

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taazz · 2015-06-18 07:02

Quote from: vkhoa on June 18, 2015, 08:54:28 amI want to know if this
dll could be used in visual basic or C(or other windows programming
language).

No it can't. You have to stop using the string data type if you want
to be compatible. In short you can only use C compatible data types ee
Char, pchar etc.

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vkhoa · 2015-06-18 07:20

:)Thanks for the reply!
Is visual basic compatible data types is the same as  C compatible
data types ?
And can we declare and pass the procedure type parameter in those
language
and assume that I use the right data type, can it call successfully
the procedure which was passed to "create" procedure when "writetext" 
is called
Can anyone tell me detail about the C an VB compatible data types, for
example for byte, longint, ect...

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taazz · 2015-06-18 07:37

As far as I know yes Visual basic has the ability to pass a
procedure/function address to your code. Make sure that you include
the calling convention on your requirements and you are set.