How to return a string from a DLL to Inno Setup?

Question

I need to return a string value to the calling Inno Setup script. Problem is I can't find a way to manage the allocated memory. If I allocate on the DLL side, I don't have anything to deallocate with on the script side. I can't use an output parameter, because there is no allocation function in the Pascal Script either. What should I do?

Answer 1

Here is a sample code of how to allocate a string that returns from a DLL:

[Code]
Function GetClassNameA(hWnd: Integer; lpClassName: PChar; nMaxCount: Integer): Integer; 
External 'GetClassNameA@User32.dll StdCall';

function GetClassName(hWnd: Integer): string;
var
  ClassName: String;
  Ret: Integer;
begin
  { allocate enough memory (pascal script will deallocate the string) }
  SetLength(ClassName, 256); 
  { the DLL returns the number of characters copied to the buffer }
  Ret := GetClassNameA(hWnd, PChar(ClassName), 256); 
  { adjust new size }
  Result := Copy(ClassName, 1 , Ret);
end;