On 5/20/15 9:56 AM, Niall Douglas wrote:

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Question: Given the API will so radically change, is now the time for a community review? Do note that APIBind allows me to support the existing API and the new API concurrently without issue.

Given the above, I would very strongly recommend that you postpone

review until you feel that the submission reflects what you want

Many replies, thank you everyone, replied to each in a single email to avoid repeating myself: On 20 May 2015 at 10:55, Robert Ramey wrote: the the

library to look like. How would you feel if it was rejected - wouldn't you just kick yourself for not delaying for the submission of the presumably best version you can submit.

I feel the current API *is* the best version I can submit given the constraints (VS2013, ABI stability) imposed. I also have done *three* full release iterations now to get AFIO ready for peer review. They take weeks, each one, with dozens of hours of unit and stability soak testing done each time. I am kicking myself for having effectively prepared a new Boost library for review three times now, with arguably three times the work of others in the review queue. I'd really like to see the ball start rolling. I have been waiting in the queue two years now. I'd like to see a review so I know what I am doing wrong, and what I should be doing instead.

As far as I know in the whole history of Boost there is only one time that a library was reject only to be accepted after a subsequent submission. Save yourself the agony of doing this more than once.

I would expect a conditional acceptance. And I'll tell you why: I am unaware of anyone using AFIO in production code. Until at least one person is, I myself would not recommend unconditional acceptance. The problem here really is chicken and egg, plus asynchronous file and filesystem is a very, very niche use case. I would wonder if any Boost library is needed by so few users in fact. However for that tiny number of users, async file and filesystem is a god send. I have some benchmarks in the tutorial which show just how much control async can give the programmer - find in files regex is quite literally warm cache double the speed of a naïve multithreaded algorithm with almost no cold cache penalty over single threaded, unlike the -50% cold cache penalty of a naive multithreaded algorithm. The race freedom guarantees on filesystem are also a god send for that tiny minority who care. On 20 May 2015 at 22:33, Andrey Semashev wrote:

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Question: Given the API will so radically change, is now the time for a community review? Do note that APIBind allows me to support the existing API and the new API concurrently without issue.

IMO, the library should be in a more or less finalized state to be reviewed. After all, the review verdict shows acceptance or rejection of the library in its form during the review, not something entirely different that it will become in the future.

Be aware that even with the next release after the next release new API variants are not finished, as I intend to add a Microsoft COM API with C API wrappers in a still further away release. That will mean no less than four separate APIs with which to work with AFIO: (i) ABI stable (the current one, will remain more or less in the future) (ii) Monadic programming (next release) (iii) Fiber programming (via proposed Boost.Fiber) which also doubles as the synchronous API WG21 want (next release). (iv) Microsoft COM API with C bindings (release after next release). I would also see any review being that of the library in its present form. Any future changes are, well, in the future and not in the scope of any review now. I would certainly hope that any review now might find problems very useful to know about now before any API refactor begins. On 20 May 2015 at 21:35, Asbjørn wrote:

The OSS project I worked on had enough issues with Boost.Filesystem v2 to v3 transition for it to be somewhat of a pain, and something to be avoided if possible.

If AFIO was included into Boost with an already obsolete API I'd stay away anyway until the new API was released.

Firstly, the current API isn't obsolete. It's fast, ABI stable, and very portable being deliberately designed to be usable from C. Future editions of AFIO will retain a mostly API compatible level with the only breaking change being std::future turning into afio::future and that error_code is now returnable from the afio::future in addition to exceptions. The monadic and fiber APIs almost certainly will wrap the current API, and therefore will be slightly slower. Boost libraries already undergo substantial API evolution. Look at Boost.Thread - it provides four API versions, all with breaking changes. I am unaware that any of those underwent a formal review, rather a post was made here informing people of any change in the default version provided (which indeed was rolled back last time). Also AFIO in its present form is 100% compatible with any future AFIO implementation even in the same translation unit. I can actually *guarantee* you that your code will not break in future Boost releases, unlike almost any maintainer here because I can ship N separate versions of AFIO and none will conflict. Do also remember AFIO is completely independent of Boost. You can use AFIO, including any past version, at any time including in combination with any future version with no ODR violation. This makes it very unlike Filesystem, or any other library here. On 21 May 2015 at 1:30, Peter Dimov wrote:

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The internal engine is the same very well tested code, just the API is very different from before. The current API was forced by VS2010's limitations and the lack of constexpr in MSVC - now VS2015 RTM has C++ 11 constexpr, I can adopt the custom future based API I always originally wanted. This new API will require C++ 14 in the compiler.

What is your contingency plan if people loudly demand C++11 support (or even C++03 support)?

Most of the upcoming C++ 11 mandatory libraries require C++ 14. One already conditionally approved (Fiber) requires C++ 14. I think people also think in terms of compilers supported rather than C++ editions used.

Would it be possible to for the new API to degrade more or less gracefully to C++11, or is it C++14 or nothing?

The answers to these questions may prove useful for your final decision.

In the refactor I'm aiming for the subset of C++ 14 provided by VS2015 RTM. That's about clang 3.4 levels minus variable templates and relaxed constexpr. This new API refactor won't happen till 2016 BTW. No time between now and then to go any faster. Plus I need Expression SFINAE, and VS2015 SP1 may have that so no point jumping before MSVC is ready. Right now AFIO v1.3 demands >= clang 3.2, >= GCC 4.7, >= VS2013. The -std=c++11 is sufficient, though -std=c++14 will produce faster code. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

On 21 May 2015 at 9:57, Gonzalo BG wrote:

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I am unaware of anyone using AFIO in production code.

This is how I see it: your library might be included in a Boost release almost in 2016.

More like 2017 assuming a conditional acceptance. I have very little free time.

Those who need asynchronous file i/o on already existing VS2013 projects are already doing "their own thing".

To be honest, VS2013 is usually far too new for most in this niche. They need more like VS2005 support, or earlier. They also generally want a C API, not a C++ API. This is my motivation for Microsoft COM bindings, and thence a C API wrapper. libuv is great, but I believe AFIO is better.

Two years ago this might have made sense to some people (I know it did not make sense to some), but right now I think it is worth asking:

Do you happen to know of any particular VS2013 project willing to do this?

I'm not sure I understand the question? Willing to do what?

To me the single most important thing is that _you_ are going to be maintaining this library for the next 10 years if it gets accepted. Having to maintain a library filled with macros and hacks for the sake of old compiler support is painful enough. Having to do this twice for 2 different APIs is a lot of work.

I'm actually pretty happy with the lack of macros and hacks in the v1.3 engine. All that portability layer stuff is abstracted into APIBind. I also fully expect to support the present API, or a close variant, permanently as it's the ABI stable API. In other words it's the only API in AFIO ever marked up with BOOST_AFIO_DECL for DLL export.

So I wish that you would focus on the API you want to have with the hope that this will keep you motivated longer and the whole community will benefit more in the long term.

From what I understood, a different interface for VS2013 can be provided either as an extension, or as a different library. Such a library/extension doesn't even need to be part of Boost if you don't want it to, and maybe those willing to use your library with VS2013 might take over the maintenance of this extension giving you time to work on other things.

I did an informal poll at C++ Now of those working with MSVC at their day jobs, some deploying at a very large scale. A very large number currently target VS2005, indeed many said it was the most stable MSVC in the past decade which is why they settled on it (and why not, it's a very good C++ 03 compiler). Their plans, overwhelmingly, are a jump from VS2005 straight to VS2015 with no intervening MSVC. Their tests on VS2015 RC have had excellent stability and often a substantial improvement in performance, and in most cases their clang/GCC C++ 11/14 code paths work well on VS2015 without much work. As much as VS2013 is a fine compiler, VS2015 is enormously better again.

TL;DR: cut out all of the C++11 legacy code and save your future self a lot of time: require clang 3.7, C++14, and submit a minimal library that you are willing to maintain for the next 10 years.

Best regards and keep up the good work, I can't wait to see those constexpr futures in action!

The only expected major breaking change in the current API is the replacement of standard futures with the custom future. The custom future can return a T, an error_code, or an exception_ptr. With standard futures the error_code is encapsulated as a system_error. I certainly can see that the community might demand a "finished" API. But firstly when is anything ever "finished"? And secondly, I believe I can convert the async_io_op struct over to an afio::future<T> standin type now before review begins, the afio::future<T> won't be the eventual implementation, but it would mean that the API is "finished" and ready for review. That's currently where I am heading mentally. And thank you community for your feedback. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/