[fpc-devel] Bug in PWidechar and refcounting

[Joost van der Sluis]

Hi all,

the bug-report on the website doesn't work, so I write a mail:

If you assign a widechar to a pwidechar, the refcount isn't
increased. This construct is often used in the variants-code, which is
allowed, according to the comments at the top of wstrings.inc.

An example:

Program test;

var PW    : PWideChar;
    dummy : AnsiString;

procedure Set_PW;

var
  W : WideString;
  s : ansistring;

begin
  s := 'Hello world'; // Can't assign directly to W, because that's
  W := s;             // interpreted as a constant with a refcount of -1

  PW := PWideChar(W); // <- Bug, refcount of W (and PW) isn't increased
end;                  // <- Memory at @W is deallocated, since refcount=0 

begin
  Set_PW;
  SetLength(Dummy,3);   // The dummy is allocated at the same address as PW
  writeln(pchar(PW)[0]); // Should write 'H', but it doesn't
end.


JoJo,
  Joost.