Singleton in Action?

[kdevel]

On Monday, 4 February 2019 at 10:17:53 UTC, bauss wrote:
> On Saturday, 2 February 2019 at 16:56:45 UTC, Ron Tarrant wrote:

[...]

>> Here's the singleton code I've been playing with:
>>
[...]
>> 	static bool instantiated_;
>>
>> 	// Thread global
>> 	__gshared DSingleton instance_;
[...]
>> 		if(!instantiated_)
[...]
>> 				if(!instance_)

[...]

> Ex. you state "instantiated_" is thread-local but that's the 
> flag you use to check whether it has been instantiated.

User angel has pointed to 
https://davesdprogramming.wordpress.com/ and the talk 
https://www.youtube.com/watch?v=ZHmIAdlNtiM which entails the 
reasoning about that pattern.

> That will not work.

Will it not work in therory (in which?) or in practice (in which)?

> Instead it should actually be shared, especially because you 
> use it in a synchronized statement.

The purpose of the pattern is to avoid synchronisationin all but 
the first call to get().

> Also:
>
> DSingleton singleton = new DSingleton;
>
> Defeats the purpose of singleton.

Sure, but it is not lazy.