TDPL: Manual invocation of destructor

[Michel Fortin]

On 2010-08-09 21:20:31 -0400, Andrei Alexandrescu 
<SeeWebsiteForEmail at erdani.org> said:

> clear() would not subvert the type system.

Oh sure it does!

1. You acknowledged yourself one of my argument a few days ago that if 
the class has an immutable member it'll be wiped out. Someone else 
somewhere could have a reference to that member, and it's value will 
change which could cause bad things...

2. If someone somewhere has a reference to an object, clearing that 
object is basically the same as replacing that reference with a 
reference to a new, uninitialized object. This could break invariants 
of any code still using that reference. In normal times, those 
invariants could be protected with judicious usage of 'private', 
'protected' or 'package' in the object (or something more 
sophisticated), but all that gets subverted by clear().

So clear() can have long-reaching effects (break program invariants) if 
used at the wrong place, and it's difficult to protect against people 
using it at the wrong place.

I know for one thing that clearing any object used by the D/Objective-C 
bridge is a potential crasher (if you call a function on a cleared 
wrapper). I would suspect the same for QtD.

-- 
Michel Fortin
michel.fortin at michelf.com
http://michelf.com/