Re: [boost] [review] Fast track review of Boost.Utility/Singleton begins today

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2008-01-17 04:20:13

Johan Nilsson wrote:
> Tobias Schwinger wrote:
>> Edson Tadeu wrote:
>>> Tobias,
>>>
>>>   Does it support a single singleton across multiple DLL's? I.e.,
>>> singleton S is accessed the first time by DLL A (and is created),
>>> then it is accessed by DLL B. Does DLL B create a new instance of
>>> singleton S for it, or can it use the one created by DLL A as a
>>> truly global singleton?
>> Yes. See the documentation for details.
> 
> Unless you have updated the documentation since the announcement, I think it 
> would be a good idea to explain this in better detail. An 'implementation 
> details' section would be a great addition to the document.

OK, I'll take this as the "how does it work"-question :-).

It's actually quite easy: The macros introduce a member function that is 
defined in compiled code and used to access the Singleton. This way, all 
code to manage a Singleton's lifetime is in one place.

The SubsystemTag works even simpler: It just changes the symbol names so 
multiple independent "families" of Singltons can coexist in one program.
It is important, because otherwise the main program's infrastructure may 
"adopt" a Singleton of a dynamic library which will crash the program if 
the library got unloaded before termination.

Regards,
Tobias