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

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2008-01-17 03:20:52

Gennadiy Rozental wrote:
> "Tobias Schwinger" <tschwinger_at_[hidden]> wrote in message 
> news:fmkefr$cf3$1_at_ger.gmane.org...
>>> For instance, the design
>>> could be made more flexible by allowing thread-safety to be specified as 
>>> a
>>> policy (with appropriate default) or by delegating the responsibility to 
>>> the
>>> wrapped type.
>> OK, FWIW policies complicate things. And what's their benefit here?
> 
> I disagree. In general policies promote modularization. In this concrete 
> case policy based solution would allow more flexibility in how "thread-safe" 
> I want to be.

They often also promote over-complication:

Thread-safety that is more complex than applying a simple mutex is very 
case-dependent and should be implemented manually.

> 
>>> If BOOST_HAS_THREADS is defined, it looks as though I have no
>>> choice but to use mutexed instantiation and/or access.  If I'm not
>>> interested in synchronised access, then the lease interface is useless.
>> Wrong:
>>
>> The lease interface is useful to improves performance. The test whether
>> the Singleton has been initialized (which requires synchronization) can
>> be performed only once.
> 
> The lease interface only improves preformance in your design. With Meyer's 
> singleton instance() is as efficient. With any other solution that returns 
> T&, I just need to store local referene to the target type.

Storing the instance is out of the question with automatic locking.

[... tons of text]

     http://learn.to/quote

Regards,
Tobias