Re: [boost] [system] The new Boost.System is now ready

Subject: Re: [boost] [system] The new Boost.System is now ready
From: Gavin Lambert (boost_at_[hidden])
Date: 2018-10-07 23:30:33

On 5/10/2018 11:37, Peter Dimov wrote:
>> The new Boost.System is now complete, on the develop branch:
>>
>> https://www.boost.org/doc/libs/develop/libs/system/
>>
>> - header-only
>> - even more constexpr than 1.68
> 
> https://pdimov.github.io/cpp-papers/P1195R0.html
> 
>> - identifier-based category comparison
> 
> https://pdimov.github.io/cpp-papers/P1196R0.html
> 
>> - message() into a caller-supplied buffer
> 
> https://pdimov.github.io/cpp-papers/P1197R0.html
> 
>> - failed()
> 
> https://pdimov.github.io/cpp-papers/P1198R0.html
> 
>> The plan is to merge it to master at some point if no breakage is 
>> encountered on develop, so that it can go into the next release.

Looks good.

I assume that the link to random.org implies that the proposed 
identifiers for generic_category and system_category were selected this way.

I suggest calling this out a bit more explicitly as the preferred method 
of choosing identifiers for custom categories, as on the first reading I 
overlooked this and was wondering how they had been chosen.  I also 
suspect that unless strongly encouraged to pick only random numbers, 
people are going to naturally try to pick "cute" identifiers (eg. ASCII 
encodings of words, a la FOURCC) or dumb identifiers (small integers), 
which have a much higher probability of collision.

Also, in P1197R0, perhaps I'm missing some context (not having a copy of 
the standard handy) but it seems peculiar that the Effects of the two 
new message() overloads are ordered differently with respect to possibly 
returning a literal message pointer, ignoring buffer and len.  Why is it 
that the second can do this but not the first?