Don't expect class destructors to be called at all by the GC

[Steven Schveighoffer]

On 12/20/17 9:57 PM, Mike Franklin wrote:
> "Don't expect class destructors to be called at all by the GC"
> 
> I was a bit shocked to read that here: 
> https://p0nce.github.io/d-idioms/#The-trouble-with-class-destructors
> 
> The document tries to clarify with:
> "The garbage collector is not guaranteed to run the destructors for all 
> unreferenced objects."
> 
> Unfortunately, that doesn't really shed much light on this oddity.  So, 
> specifically, under what circumstances are destructors not called?

It's implementation defined :)

The gist is, you cannot expect that destructors will be run in a timely 
manner, or at all.

They may be called, and most of the time they are. But the language nor 
the current implementation makes a guarantee that they will be called.

For this reason, any classes that use non-memory resources should clean 
up those resources before becoming garbage. This is why most of the 
time, such items are managed by structs.

Note that the same non-guarantee exists in other GC'd languages, such as 
Java or C#.

-Steve