Static destructors called before class instance destructors

[rkreis]

Sean Kelly schrieb:
> rkreis wrote:
>> Good day.
>>
>> Using derelict, I noticed bad behavior: The app segfaulted inside of 
>> destructors. I later found out that derelict unloaded libraries and 
>> the destructor, freeing resources, tried to call such unloaded 
>> functions. This happens because a static destructor unloads all 
>> libraries. A simple test case shows that static destructors can be 
>> called before all instances are destructed. If an instance destructor 
>> then uses resources freed by the static destructor, things become 
>> problematic.
>>
>> import std.stdio;
>>
>> class Dude {
>>     private static char[] eek;
>>
>>     public this() {
>>         writefln("Dude ctor");
>>     }
>>
>>     public ~this() {
>>         writefln("Dude dtor - eek is '%s'", eek);
>>     }
>>
>>     public static this() {
>>         writefln("Dude static ctor");
>>         eek = "Everything up and running";
>>     }
>>
>>     public static ~this() {
>>         writefln("Dude static dtor");
>>         eek = "You're doomed";
>>     }
>> }
>>
>> void main() {
>>     Dude d = new Dude();
>> }
>> outputs
>> Dude static ctor
>> Dude ctor
>> Dude static dtor
>> Dude dtor - eek is 'You're doomed'
> 
> Funny, I've recently been trying to decide how to handle this exact 
> situation.  When a D application shuts down, unreachable objects 
> may/will be collected then static dtors are run.  After that, there may 
> still be valid D objects floating around, either which the GC 
> incorrectly thought were reachable or that were reachable through static 
> references.  Should these objects never be finalized?  This would 
> certainly be the easier/cleaner approach to take, but I'm not sure how I 
> feel about leaving objects un-finalized.
> 
> 
> Sean

I vote against silently leaving them unfinalized just because they might 
depend on static variables. Maybe print a (runtime) warning or error 
(like unhandled switch cases), or just finalize them, making it the 
developer's job to care that objects still reachable after the static 
destructors have run won't depend on static variables.
Either way, I would like all unreachable objects to be collected before 
static destructors are run. And I'd also like to see more 
opinions/suggestions on this.

Have a nice day