Re: [boost] [parameter] Go C++11 and above only, or keep C++03 support?

Subject: Re: [boost] [parameter] Go C++11 and above only, or keep C++03 support?
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2018-11-03 14:35:06

On 11/3/18 5:17 PM, Andrey Semashev wrote:
> On 11/3/18 4:21 PM, degski wrote:
>> On Sat, 3 Nov 2018 at 14:41, Andrey Semashev via Boost 
>> <boost_at_[hidden] <mailto:boost_at_[hidden]>> wrote:
>>
>> Â Â Â  On 11/3/18 2:47 PM, Cromwell Enage via Boost wrote:
>> Â Â Â Â  > Hello, Andrey.
>> Â Â Â Â  >
>>      > It's possible to retain the old code for C++03 compilers.  Which
>> Â Â Â  ones do
>> Â Â Â Â  > your library users have?
>>
>> Â Â Â  I don't have this data. Boost.Log is documented to support gcc since
>> Â Â Â  4.5
>> Â Â Â  and MSVC since 8.0 SP1. It might be ok to raise the minimum 
>> requirement
>> Â Â Â  a bit, if it makes it easier to support in Boost.Parameter and other
>> Â Â Â  lower level libraries, but switching sraight to C++11 might be big 
>> deal
>> Â Â Â  for users.
>>
>>
>> The following question has been asked many times by many posters and 
>> there never is an answer: "Those users who want to stick to the old 
>> ways of doing things and like to use unsafe compilers [Meltdown, 
>> Spectre come to mind], why can't they just use old versions of Boost?"
> 
> As it was answered, also many times: because we don't do support 
> releases. Basically, if a bug is discovered, our recommendation is 
> always "use a more recent Boost release". Of course, users can apply 
> patches to their versions of Boost but this is a significant maintenance 
> burden and may not be acceptable to everyone.
> 
> Having new features and libraries might also be desirable. That the 
> user's code base is C++03 doesn't necessarily mean it doesn't evolve.
> 
>> There was, as far as I read it, considerable support to at least move 
>> to C++11, which is already 2 standards behind the current standard 
>> [and is by now fully supported on the main platforms]. Whatever is 
>> documented is not relevant, if the docs are out of date, they have to 
>> be updated. If every time this kind of question pops up, the answer 
>> is, "let's keep backward compatibility", then when are we gonna move 
>> to a newer standard? Or to put it differently, a direct question to 
>> you Andrey, at which point in time [which new std, 20, 23, 26, 29, 
>> 32???] do you think it will be opportune to move to C++11 and break 
>> with C++98 [because doing nothing will always be easier]?
> 
> If by "move" you mean actively stripping Boost from C++03 support then 
> probably never. But as far as I'm concerned, Boost has moved to C++11 
> and later as soon as the first C++11 was accepted.

That should read "the first C++11 library was accepted".

> At that point in 
> time, the rest of Boost, still compatible with C++03, did not disappear 
> and stayed relevant. C++03-compatible libraries are still a part of 
> Boost and very much relevant, despite how many C++ versions have come out.
> 
> Specifically for Boost.Log, it already does use some of the C++11 
> features, when available. And I even think it started doing so before 
> C++11 was finalized. But I still consider C++03 compatibility a plus 
> rather than a minus.
> 
> On a personal note, I find this "C++11 holy cow" hype quite a pointless 
> waste of breath (or... network bandwidth, I guess). There is no point in 
> dropping libraries on the ground of C++03 compatibility, so that's never 
> going to happen. Boost never rejected libraries that targeted newer C++ 
> versions, that's not changing either. Declaring that we're not testing 
> C++03 compilers anymore might make sense, but we actually do. So I don't 
> quite understand what were the recent discussions about "dropping C++03" 
> about. Just stop debating and start writing some great code, guys! Our 
> users will be only happy. :)
> 
>> Â Â Â  I'm not adamantly against it, not to the point I would
>> Â Â Â  rewrite Boost.Log just to stay C++03 compatible. But it would seem 
>> that
>> Â Â Â  the C++11 requirement is not that necessary in Boost.Parameter 
>> either -
>> Â Â Â  you can just keep the existing code in C++03 mode it it'll work as
>> Â Â Â  before.
>>
>> I guess, it's always possible to write more code [that's what you ask 
>> all maintainers to do] and work around the C++11 specificities?
> 
> It's a tradeoff, of course. In some cases, C++11 or whatever might be 
> crucial for the library design or functionality. The particular case 
> with Boost.Parameter doesn't seem to me like one, so yes, I'd *prefer* 
> to keep the compatibility with C++03. If there appears a case that would 
> make keeping the support for C++03 unreasonable (in Boost.Parameter or 
> elswhere), I will accept it and Boost.Log, by induction, will become 
> C++11-only.