Destruction Sequence: module and classes defined within

[Lutger]

Lars T. Kyllingstad wrote:

> On Tue, 05 Oct 2010 23:25:36 +0200, vano wrote:
> 
>> The code below:
>>      module used;
>> 
>>      import std.stdio;
>> 
>>      class ClassA {
>>          this()  { writeln("A ctor"); }
>>          ~this() { writeln("A dtor"); }
>>      }
>> 
>>      static this()  { writeln("used.sctor"); } static ~this() {
>>      writeln("used.sdtor"); }
>> 
>>      void main() {
>>          auto a = new ClassA();
>>      }
>> produces the following output (DMD v2.049):
>>      used.sctor
>>      A ctor
>>      used.sdtor
>>      A dtor
>> 
>> The question is: should the module be allowed to be unloaded before all
>> module-level objects/structures are destructed/unloaded?
> 
> 
> I'm no expert on this, but I think it has to be that way.  Consider this:
> 
>   class Foo { ... }
>   Foo foo;
> 
>   static this()
>   {
>       foo = new Foo;
>   }
> 
>   static ~this()
>   {
>       foo.doStuff();
>   }
> 
> So you see, if foo had already been destroyed and garbage collected, my
> program would have crashed when the module static destructor was run.
> Thus, I guess, running the garbage collector for the final time has to be
> one of the last things done on program shutdown, after running all module
> destructors.
> 
> -Lars

In this case however, foo is still referenced whereas in the original example 
'a' is unreferenced after main exits.

I could only find this in the spec: "The garbage collector is not guaranteed to 
run the destructor for all unreferenced objects." *

>From reading the spec, I think that all one can conclude is that after main 
unreferenced objects may be finalized any time, or not at all.

* http://www.digitalmars.com/d/2.0/class.html#Destructor