library Lib;

uses

  SysUtils, Classes;

{$R *.res}

procedure Test(p: PChar);

const

  Title = 'Title ';

var

  str: string;

begin

  str := p;

  StrCopy(p, Title);

  StrCat(p, PChar(str));

end;

exports Test;

begin

end.

unit Unit1;

interface

uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;

type

  TForm1 = class(TForm)

    Button1: TButton;

    procedure Button1Click(Sender: TObject);

  end;

var

 Form1: TForm1;

implementation

{$R *.dfm}

procedure Test(p: PChar); external 'Lib.dll';

var num: Integer;

procedure TForm1.Button1Click(Sender: TObject);

var

  p: PChar;

begin

  Inc(num);

  p := StrAlloc();

  StrCopy(p, PChar(IntToStr(num)));

  Test(p);

  Text := p;

  StrDispose(p);

end;

end.