Re: [boost] Re: shared_ptr and BOOST_DISABLE_THREADS

From: Howard Hinnant (hinnant_at_[hidden])
Date: 2004-04-26 07:13:15

On Apr 25, 2004, at 9:29 PM, Peter Dimov wrote:

> In fact, it isn't even clear to me why you need to synchronize access 
> to the
> implementation at all, as std::locale is immutable; it has no non-const
> member functions.

Ah, I think I see the confusion.  locale is mutable.  The copy ctor 
mutates the rhs (though not visibly) and the assignment mutates both 
sides.  There's more refcounting running around under locale's hood 
than just the shared_ptr to the implementation.  In addition each facet 
is individually refcounted (but not with shared_ptr).  Even 
std::use_facet potentially mutates a locale (via lazy addition of a 
standard facet to the locale).  This latter technique is one of the  
main (portable) ways typically used to drop the code size of HelloWorld 
down from astronomical.

http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/PDTR18015.pdf

-Howard