function GetLastLogText(AMaxSize: NativeUInt; ABuffer: PAnsiChar): NativeUInt;
                                 {$IFDEF MSWINDOWS}stdcall;{$ELSE}cdecl;{$ENDIF}

function GetLastLogText(AMaxSize: integer; ABuffer: PWideChar): integer;
         stdcall; external 'c:\dllFR1292016_ХХХХ.dll';

...
function LastLogText () : string;
  var
    Buffer  : PWideChar;
    Len     : integer;
  begin
    GetMem(Buffer, __MaxSize);
    Len := GetLastLogText(__MaxSize, Buffer);
    Result := Copy(Buffer, 1, Len);
  end;

function GetLastLogText(AMaxSize: NativeUInt; ABuffer: PAnsiChar): NativeUInt;
         stdcall; external 'c:\dllFR1292016_ХХХХ.dll';

function GetLastLogText(AMaxSize: NativeUInt; ABuffer: PAnsiChar): NativeUInt;
         stdcall; external 'c:\dllFR1292016_ХХХХ.dll';
...
function LastLogText () : string;
  var
    Buffer  : PAnsiChar;
    Len     : NativeUInt;
  begin
    GetMem(Buffer, __MaxSize);
    Len := GetLastLogText(__MaxSize, Buffer);
    Result := Copy(Buffer, 1, Len);
  end;

program Test_dllFR1292016_XXXX;

{$APPTYPE CONSOLE}

uses
  SysUtils;

type
  NativeUInt = cardinal;

function GetLastLogText(AMaxSize: NativeUInt; ABuffer: PAnsiChar): NativeUInt;
         stdcall; external 'c:\dllFR1292016_XXXX.dll';

function GetLastErrorText(AMaxSize: NativeUInt; ABuffer: PAnsiChar): NativeUInt;
         stdcall; external 'c:\dllFR1292016_XXXX.dll';

function GetLastErrorCode: HRESULT;
         stdcall; external 'c:\dllFR1292016_XXXX.dll';

const
  __MaxSize = 4000;

  function LastLogText () : string;
  var
    Buffer  : PAnsiChar;
    Len     : NativeUInt;
  begin
    GetMem(Buffer, __MaxSize);
    Len := GetLastLogText(__MaxSize, Buffer);
    Result := Copy(Buffer, 1, Len);
  end;

  function LastErrorText () : string;
  var
    Buffer  : PAnsiChar;
    Len     : NativeUInt;
  begin
    GetMem(Buffer, __MaxSize);
    Len := GetLastErrorText(__MaxSize, Buffer);
    Result := Copy(Buffer, 1, Len);
    Result := Format('[%d] ', [GetLastErrorCode]) + Result;
  end;

function CalcDensityNP(
         const ADensityUp, ADensityMid, ADensityDown : double;
         const ALevelTotal, ADiametr : NativeUInt;
         var ADensityNP : double) : HRESULT;
         stdcall; external 'c:\dllFR1292016_XXXX.dll';

var
  Res : HRESULT;
  DensNP : double;
begin
  try
    Res := CalcDensityNP(675, 675, 884.78, 700, 80, DensNP);
    WriteLn(Format('DensNP=%.4f', [DensNP]));

    WriteLn(LastLogText());
    if Res <> 0 then
      Writeln(LastErrorText());
    Readln;
  except
    on E:Exception do
    begin
      Writeln(E.Classname, ': ', E.Message);
      Readln;
    end;
  end;
end.