Re: [boost] [config] RFC PR 82

Subject: Re: [boost] [config] RFC PR 82
From: Vinícius dos Santos Oliveira (vini.ipsmaker_at_[hidden])
Date: 2016-08-01 16:13:26

Sorry about necrobumping, but I've ignored this thread previously as the
subject line didn't make it obvious this thread was of my interest.

2015-11-24 17:20 GMT-03:00 Andrey Semashev <andrey.semashev_at_[hidden]>:

> I don't think for  is a good idea, given that the
>>> same effect can be achieved in pure C++.
>>>
>>
>> You mean creating a class template with a single dummy template argument
>> and a static data member just so that you can define a global variable in
>> a header w/o linker errors?
>>
>
> Slightly better:
>
>   template< typename T, typename Tag = void >
>   struct singleton
>   {
>     static T instance;
>   };
>   template< typename T, typename Tag >
>   T singleton< T, Tag >::instance;

I was looking for something similar to BOOST_OVERRIDABLE_SYMBOL as I want
my library header only and Boost.System requires the category to be a
single static object and it'll even use address comparison to test if the
categories are the same:
https://github.com/boostorg/system/blob/388b3497af4b205ff7e8c67ea306f57eea629ae3/include/boost/system/error_code.hpp#L392

Is it guaranteed the above code will return the same object even if this
code was included in different libraries used by the same program?

-- 
Vinícius dos Santos Oliveira
https://vinipsmaker.github.io/