In the code below Bar creates a reference counted object and returns an
interface to it. Foo calls Bar but doesn't assign the result anywhere.
In Delphi, this produces the result:
Foo >
TAutoRelease.Create
Foo <
TAutoRelease.Destroy
But in Free Pascal it produces this:
Foo >
TAutoRelease.Create
TAutoRelease.Destroy
Foo <
If I change Foo to assign the interface to a local variable but don't do
anything with that variable, Free Pascal produces the same results as
Delphi.
Delphi's behavior is what I expected, and allows tricks with triggering
behavior when leaving the current scope. Barry Kelly has one example on
his blog where he talks about implementing C++'s RAII using it:
http://blog.barrkel.com/2010/01/one-liner-raii-in-delphi.html
Is Free Pascal's behavior intentional? Can it be changed to match Delphi?
Thanks,
Zoë Peterson
Scooter Software
============================================
program AutoRelease;
{$IFDEF FPC}{$MODE DELPHI}{$ENDIF}
{$APPTYPE CONSOLE}
uses
Classes,
SysUtils;
type
TAutoRelease = class(TInterfacedObject)
constructor Create;
destructor Destroy; override;
end;
constructor TAutoRelease.Create;
begin
WriteLn('TAutoRelease.Create');
end;
destructor TAutoRelease.Destroy;
begin
WriteLn('TAutoRelease.Destroy');
inherited;
end;
function Bar: IInterface;
begin
Result := TAutoRelease.Create;
end;
procedure Foo;
begin
WriteLn('Foo >');
Bar;
WriteLn('Foo <');
end;
begin
Foo;
end.
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