April 2022 - Boost - lists.boost.org

So.... what are we going to do about modules?
by John Maddock 06 Apr '22

06 Apr '22

The title says it all really, but in more detail: 1) Is there any existing best practice we should follow yet? 2) Can we share code content effectively between headers and modules? And by modules I mean "proper" ones: we should be able to write "import boost.whatever;" rather than importing a header. 3) What directory structure should we all be using for module definition files? 4) Do we have Boost.Build support yet? 5) What file extensions should we be using? 6) I presume we would all use the boost.libraryname and boost.libraryname.sub_feature naming convention with boost.libraryname pulling in the whole library? 7) Does anyone have a handle on the current state of std library modularization? 8) Is there demand for this? And no doubt lots of other things I haven't thought of. Curiously yours, John.

11 27

Permission to merge bug fix to Outcome
by Niall Douglas 06 Apr '22

06 Apr '22

Issue being fixed is https://github.com/ned14/outcome/issues/259 where enabling of move assignment was not calculated correctly. (To be specific, if both T and E implement move assignment and default construction, but not move nor copy construction, we did not enable move assignment before and with this fix now we do) Code fixing it is at https://github.com/ned14/outcome/pull/260 Fix passes on develop branch at https://www.boost.org/development/tests/develop/developer/outcome.html Niall

2 4

Should boost have ofind(_if), that returns boost::optional<T&>?
by Ivan Matek 06 Apr '22

06 Apr '22

Hi, I have been thinking for this for a long time so I wanted to get the feedback from others. As you probably know better than me there is a bit of a drama <https://brevzin.github.io/c++/2021/12/13/optional-ref-ptr/>when it comes to std::optional<T&> and from what I see it will not be in C++23 for sure. I believe this gives an opportunity to boost to provide something nice for the users. Now the issues are the following: AFAIK boost only has old ranges and iterator based algorithms, ideally we would just have something like std:: ranges and add the ofind/ofind_if to those, but AFAIK those do not exist. So I think best thing would be to add it to boost::algorithm <https://github.com/boostorg/algorithm/tree/develop/include/boost/algorithm> . There are further questions like, should boost containers like map/unordered_map gain similar functionality, but I think deciding if we want the general algorithm is the first step. Another option I can think of is that those algorithms return something like a 0 or 1 element view(so you could access the optional value with range based for loop). This seems weird to me, so I would prefer boost::optional<T&>. There is s a short example on godbolt <https://godbolt.org/z/W9K3na9Gc>, but don't look at implementation too much, it was just something I hacked quickly, I am mostly interested in in feedback on if functionality would be nice addition to boost. regards, Ivan

5 9

regarding performance of boost::recursive_mutex::scoped_lock
by Daggumati, Rajesh 04 Apr '22

04 Apr '22

Hi Team, boost::recursive_mutex::scoped_lock behavior is same in linux and windows? I am getting some delay in my project which is in windows but same project in linux is not getting delayed. Regards, Rajesh D Please be advised that this email may contain confidential information. If you are not the intended recipient, please notify us by email by replying to the sender and delete this message. The sender disclaims that the content of this email constitutes an offer to enter into, or the acceptance of, any agreement; provided that the foregoing does not invalidate the binding effect of any digital or other electronic reproduction of a manual signature that is included in any attachment.

2 1

[release][multi_index] permission to merge to master
by Joaquin M López Muñoz 03 Apr '22

03 Apr '22

Hi, the following PR is absolutely trivial https://github.com/boostorg/multi_index/pull/57 but seems like it's important to Bitcoin guys in connection with an effort to prune internal Boost dependencies they're carrying out. Can I merge to master or should I wait till Boost 1.80? Thank you, Joaquín M López Muñoz

2 2

Re: [boost] Proposing a MySQL client library for inclusion in Boost
by Marcelo Zimbres Silva 02 Apr '22

02 Apr '22

Hi Ruben, I have had a look into your library and some questions arise > https://anarthal.github.io/mysql/mysql/ref/boost__mysql__resultset/async_re… > The handler signature for this operation is void(boost::mysql::error_code, std::vector<boost::mysql::row>). > etc. Having a std::vector in the signature of the completion handler is unusual in ASIO. In general large objects should be passed as parameters in the async operation e.g. socket::async_read gets a dynamic_buffer which is a lightweight view to storage. Additionally, there is not support for custom allocators. That wouldn't be a big problem to me if I could reuse the same memory for each request but the interface above prevents me from doing so. > https://anarthal.github.io/mysql/mysql/ref/boost__mysql__connection/async_q… > The handler signature for this operation is void(boost::mysql::error_code, boost::mysql::resultset<Stream>) Hier the completion handler is returning an io object i.e. boost::mysql::resultset, which is also unusual as far as I can see. Does that play nice with executors? I would prefer having the completion handler return config parameters with which I can instantiate a boost::mysql::resultset myself in my desired executor. > https://anarthal.github.io/mysql/mysql/ref/boost__mysql__connection.html I don't see a reason for this class, or at least I fail to see what state does the mysql protocol imposes on you that would justify this class. I would prefer free funcitions much more here, for example, in the same way as beast::http::async_read. > https://anarthal.github.io/mysql/mysql/ref/boost__mysql__value/get_std_opti… > https://anarthal.github.io/mysql/mysql/ref/boost__mysql__value/get_optional… Sounds also unusual to have two member functions for the different versions of optional. Regards, Marcelo

3 7