← board

TObject-typed parameter is 32-bit-truncated in methods, unmatched in plain routines

Symptom 1 — method param truncated (silent wrong value)

type
  TObj = class
    procedure H(Sender: TObject);
  end;
var target: TObj;
procedure TObj.H(Sender: TObject);
begin
  writeln(Pointer(Sender) = Pointer(target));   { FALSE }
  writeln(Int64(Pointer(Sender)));               { lower 32 bits only }
end;
begin
  target := TObj.Create;
  target.H(target);
end.

Sender arrives as the LOW 32 BITS of the passed object pointer (e.g. 0x2B40F808 from 0x70612B40F808). A concrete-class parameter (Sender: TObj), a Pointer parameter, and a plain-function class parameter are all correct — only TObject-typed parameters truncate, so the load/store width for the builtin TObject type is wrong somewhere in the value-param path.

This is silent wrong behavior: every PCL event handler is declared (Sender: TObject) per LCL convention, and any handler that uses Sender's value (identity compare, cast, field access) reads through a truncated pointer — worked "by luck" so far because existing handlers only use Self. Eliah's tab bar now carries a workaround (Sender: TButton + comment).

Symptom 2 — plain routine rejects the call

procedure P(o: TObject);
begin end;
...
P(target);   { TObj instance }



Mismatch in MatchProcCall: name = P, nArgs = 1
  arg[0] = 6

The overload matcher does not accept a class instance for a TObject parameter in a plain routine (methods accept it — then truncate). Also note the raw matcher dump is not a normal file:line diagnostic.

Acceptance

Log