Hello,

when I make a record type managed by adding an `Initialize` operator according to [1], can I rely on the record being initialized at the beginning of a function in which the record is the function result?

Example:

type TRec = record
  // whatsoever
  class operator Initialize(var aRec: TRec);
end;
function DoSomething: TRec;
begin
  // <---- can I assume that `Result` is initialized when the function is entered?
  // more code
end;

[1] https://wiki.freepascal.org/management_operators

Consider this:
====
type

{ TRec }

 TRec = record
  // whatsoever
    class operator Initialize(var aRec: TRec);
  end;

{ TRec }

class operator TRec.Initialize(var aRec: TRec);
begin
  writeln('class operator TRec.Initialize(var aRec: TRec)');
end;
function foo: TRec;
begin
  writeln('foo');
end;

begin

  foo;

end.
===
It outputs:
C:\Users\Bart\LazarusProjecten\ConsoleProjecten>test class operator TRec.Initialize(var aRec: TRec)
foo

So, the initialization code is called before anything in the function.

Bart

Thomas Kurz via fpc-pascal schrieb am
Sa., 2. Nov. 2024, 18:47:

As with any managed type result the Result variable will be initialized *outside* of the function and passed in as a var-parameter. Depending on the code and due to how the compiler manages temporary variables involved in this, this can lead to your code receiving a Result variable upon entry that had been used by a previous call.

So to be on the safe side assign a Default(YourType) to it (needs current FPC 3.3.1 to work correctly) or use a local variable of the same type and overwrite the Result.

Regards,
Sven

Thank you. This was a very valuable and helpful comment.

Maybe we can add this information to the wiki?