widestring compatibility problem in Delphi

Question

In a dll build with Delphi 2006

Foo(aPath: widestring);
begin
  _rootPath := aPath;
end;

In an executable built with Delphi 2010

_Foo := GetProcAddress(FooModule,’Foo’);
_Foo(‘123456’);

Stepping into the dll, aPath = '123'. In fact any string I pass gets cut exactly in half.

1.) Why is my literal being halved? 2.) How do I fix it?

Answer 1

Make sure the _Foo parameter is a widestring in 2010

Answer 2

I suppose you get wrong data because WideString is a managed type and the memory manager for the dll and the executable are different. If you can recompile the dll make aPath type to be PWideChar

Answer 3

WideStrings reside in Windows heap and are not managed by Delphi memory manager. So WideStrings (unlike other long string types) can be shared between exe and dll without problems.