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Networking TS + Beast, NEW Tutorials, Read this to learn std::net !!!
by Vinnie Falco 18 Mar '19

18 Mar '19

Fellow C++, Boost, and WG21 Enthusiasts, lend me your ear! I write to inform you about exciting developments in C++ networking. First, a bit of background. Networking comes in three flavors: * Networking TS <https://cplusplus.github.io/networking-ts/draft.pdf> * Boost.Asio <https://www.boost.org/doc/libs/1_69_0/doc/html/boost_asio.html> * Standalone Asio <https://github.com/chriskohlhoff/asio> These three are for the most part identical, except that Asio flavors have additional features like ssl::stream and signal_set which are not in the TS, but will very likely appear in a future update or version. We've had Asio for over a decade now, but there is a shortage of experts. Some people believe this shortage is because Asio in particular (and thus, Networking TS since they have identical interfaces) is "difficult to use." I believe it is wrong to blame Asio for this. Concurrent programs in general are hard to write. This is applicable: "Unfortunately, today's reality is that only thoughtful experts can write explicitly concurrent programs that are correct and efficient. This is because today's programming models for concurrency are subtle, intricate, and fraught with pitfalls that easily (and frequently) result in unforeseen races (i.e., program corruption) deadlocks (i.e., program lockup) and performance cliffs (e.g., priority inversion, convoying, and sometimes complete loss of parallelism and/or even worse performance than a single-threaded program). And even when a correct and efficient concurrent program is written, it takes great care to maintain — it's usually brittle and difficult to maintain correctly because current programming models set a very high bar of expertise required to reason reliably about the operation of concurrent programs, so that apparently innocuous changes to a working concurrent program can (and commonly do, in practice) render it entirely or intermittently nonworking in unintended and unexpected ways. Because getting it right and keeping it right is so difficult, at many major software companies there is a veritable priesthood of gurus who write and maintain the core concurrent code." - Herb Sutter, "The Trouble with Locks", <http://www.drdobbs.com/cpp/the-trouble-with-locks/184401930> Although this was written in 2005 it is still relevant today. It is understandable that Asio will be the first target of anger and frustration when writing concurrent programs, since it is on the "front line" so to speak. There has also been a distinct shortage of *good* tutorials and examples for Asio. Articles or blog posts which teach you step by step, explaining everything, and giving example code which demonstrates best practices. Boost.Beast is my low-level HTTP/WebSocket library which builds on Boost.Asio: <https://github.com/boostorg/beast> In the original release of Beast, the documentation stated "prior understanding of Boost.Asio is required." However, field experience has shown that users ignore that requirement and attempt to write complex, concurrent programs as their first-time introduction to both Beast and Asio. Based on feedback from committee members, and to serve users better, the scope of Beast has been enlarged to include first-time users of networking. The upcoming Boost 1.70 release reflects this new scope and I am excited to announce some very nice things which you can access today. First of all, Beast documentation and examples no longer use the "boost::asio" namespace, they the namespace alias "net::". While this is cosmetic, it reinforces the notion when inspecting code that it is equally applicable to Boost.Asio, Asio, and Networking TS (identifiers which are not in the TS, such as signal_set, are still qualified with boost::asio). A new documentation page explains the three flavors of networking: <https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_io.ht…> This is also explained in my 2018 CppCon presentation: <https://youtu.be/7FQwAjELMek?t=444> I have added a "Networking Refresher", a complete overview of networking from soup to nuts. No prior knowledge or understanding of networking is required, everything is explained in detail so if you want to learn this is the place to start. I also kept it short, but it is loaded with hyperlinks for further learning: <https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_io/as…> There was a recent paper in Kona, P1269R0 ("Three Years with the Networking TS") about difficulty of implementing timeouts. To address this, Beast now has a stream class which implements configurable timeouts for you, and callers no longer have to fiddle with timers manually anymore. Everything "Just Works." It achieves the P1269R0 author's goal of having timeouts "built-in to asynchronous operations", but in a way that fits in with the design of the TS: <https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_io/ti…> I feel that this `beast::basic_stream` serves as an existence proof that the current design of Networking TS is sound - the TS offers a flexible toolbox which lets you build your own framework the way that you want it, without making odd choices for you. We are still discovering ways of leveraging it to maximum use. The beast::websocket::stream also has built-in timeouts, but they are enhanced to support "idle pings" (keeping client connections alive) and everything is fully configurable: <https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_webso…> All you need to do to get sensible, suggested websocket timeouts is add one line of code after creating your stream: ws.set_option(websocket::stream_base::timeout::suggested( beast::role_type::server)); To address the cumbersome boilerplate of writing composed operations (specifically the need to propagate the associated allocator and associated executor, and to avoid invoking the completion handler from within the initiating function when the operation would complete immediately) Beast adds two new utility base classes, with plentiful documentation and examples throughout: <https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_io/wr…> There are two well-rounded examples which show you step by step how to write these things in a safe way: <https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_io/wr…> <https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_io/wr…> I have a big, new open source project which implements a server, that uses the `system_context`, taking full advantage of native Windows and Mac OS system-level execution context features. To support this use case and industry feedback, the examples in Beast now default to being always thread-safe. All examples use a "strand", and leverage P1322R0 ("Networking TS enhancement to enable custom I/O executors"). Yes, this paper which was approved in Kona, is now implemented in both Boost.Beast, and Boost.Asio, including all of the Beast examples, so if you pick up Boost 1.70 (or the master branches from github) you can start playing with this as soon as you're done reading this message!! <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1322r0.html> We have an active #beast channel in the C++ Slack (https://slack.cpp.al) where experienced users can help, no question is too small! I hope you will join me and the rest of the Beast and Asio community in exploring what the very powerful Networking TS and Asio libraries have to offer, and build something great together! Regards P.S. Don't forget to star the repository! <https://github.com/boostorg/beast>

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boost::endian::native_to_big_inplace fails with char
by Martijn Otto 18 Mar '19

18 Mar '19

I am having issues with boost::endian:native_to_big_inplace when used with a char. Whatever you try to 'reverse' comes out as 0. Looking through the code, on little endian machines it calls endian_reverse (as expected). This function has no overload for a char and it then gets promoted to an int. Since the int _is_ actually larger than 1 byte, something gets reversed. The native_to_big_inplace then returns it as a char, narrowing the int and throwing away all the relevant bits, resulting in a 0. I found an issue on github about this: https://github.com/boostorg/endi an/issues/10 about exactly this issue. The bug is easily shown if you try to compile static_assert(sizeof(boost::endian::endian_reverse('y')) == sizeof('y'))

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Re: [Boost-users] [boost] Networking TS + Beast, NEW Tutorials, Read this to learn std::net !!!
by Vinnie Falco 17 Mar '19

17 Mar '19

> Somebody(tm) (ASIO or Beast) maybe should make buffer that has has member fn content() that returns a range with begin and end. Yes that is in Boost.Beast 1.70: <https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/ref/boost__…>

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numeric_limits<float128_t> return incorrect values
by Gero Peterhoff 16 Mar '19

16 Mar '19

Hello, your implementation in /boost/math/cstdfloat/cstdfloat_limits.hpp return incorrect values for: - has_denorm - denorm_min - is_bounded - signaling/quiet_NaN ? Are the other values correct? See https://github.com/gcc-mirror/gcc/blob/master/libquadmath/quadmath.h thx Gero

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Boost library name formats
by Damien 15 Mar '19

15 Mar '19

Hello, For several years now we've built Boost libraries on Windows with a minimal set of tags in the library and dll names. Our dlls and libs have looked like this: boost_atomic-mt-gd.dll boost_atomic-mt-gd.lib etc. We just upgraded from 1.65.1 to 1.69 and the same bjam command (with a new bootstrapped bjam) is now giving us an extra x64 tag: boost_atomic-mt-gd-x64.dll boost_atomic-mt-gd-x64.lib This is on VS2017 15.9.9. The bjam command we've used for years is: bjam.exe --toolset=msvc address-model=64 --stagedir=./stage64debug --build-dir=./build64debug --layout=tagged --without-mpi variant=debug link=shared threading=multi runtime-link=shared install --prefix=./win64debug/indep --exec-prefix=./win64debug/bin --libdir=./win64debug/lib --includedir=./win64debug/include Has a default setting in bjam been changed? What can we add to the bjam command to get back to the old minimal names? Thanks in advance. Damien

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Help Needed with C++ SSL-using code
by Osman Zakir 15 Mar '19

15 Mar '19

I followed the Boost.Beast examples for the SSL, sync server and client code and loaded root certificates from the Windows root cert store (or at least tried to), but now I can't even get to my app in my browser anymore for some reason. Here's the link to the GitHub repository with all of the source code: https://github.com/DragonOsman/currency_converter . Any help would be appreciated. [https://avatars0.githubusercontent.com/u/18173932?s=400&v=4]<https://github.com/DragonOsman/currency_converter> GitHub - DragonOsman/currency_converter: Application for Computer Science course<https://github.com/DragonOsman/currency_converter> Google Maps + Currency Converter Web Application. Application for Computer Science course. This is a currency converter web application with the frontend and a backend. github.com

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Re: [Boost-users] [boost] Networking TS + Beast, NEW Tutorials, Read this to learn std::net !!!
by Vinnie Falco 15 Mar '19

15 Mar '19

On Thu, Mar 14, 2019 at 5:09 PM Ivan Matek <libbooze(a)gmail.com> wrote: > Quite a weird pattern, where buffer does not have member begin, end. > Maybe a sentence or two describing the rationale and complexity would be nice. > I know it is O(1), but it is weird that begin/end are called on pointer. Yeah, well... that's a sore subject. First of all I did not invent these buffer concepts, they are part of Asio and Networking TS. And they *used* to have begin() and end(), but then the C++ Standards Committee decided that they didn't like `const_buffers_1` and `mutable_buffers_1`, so they got rid of them in the TS draft. Then they realized that having `const_buffer::begin()` would be confusing. Does it refer to the beginning of the buffer sequence, or does it refer to the first byte of that buffer? They decided to get rid of begin/end entirely for the buffer types and add buffer_sequence_begin and buffer_sequence_end in its place. And this is why we can't have nice things. > > std::size_t read_line > I am tired, but is this function O(n^2)? It starts over from the beginning of the range so there can be some overlap of the searching, yes. > cb += bytes_transferred; // adjust the pointer and size > I would maybe switch to write instead of write_some to keep the code shorter, and mention write_some as another option in text. Well the purpose of this example is to show the looping. > [](error_code ec, std::size_t bytes_transferred) > For learning purposes I would capture something in lambda by value and note that reference capture would be buggy. That is something I might consider!! Remember though I"m stuck in C++11 so no lambda capture assignment expressions. Appreciate the feedback! Regards

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Coordinating Boost Releases with compiler releases
by Marshall Clow 14 Mar '19

14 Mar '19

In the thread "MSVC 2019 and 1.70 beta", there has been a discussion about what to do about support for MSVC 2019, which is due to be released right about the same time that Boost 1.70. One person suggested that we delay the boost release until after the MSVC release (I think the suggestion was "May"). This general question has been discussed before (several times), since tools get released fairly often - and so does Boost. In general, I am not in favor of delaying boost releases in order to add support for 'about to be released' development tools. There are two main reasons for this: * There's always another compiler / tool about to be released. Clang 8 is imminent - currently at RC5. GCC 9.1 is scheduled to be released in early May. * Boost releases happen every four months. August is not really that far off. People who want support for tool XXXX can use "the trunk", getting it either from git or from bintray. [ Everyone knows about the tarballs at bintray, right? https://dl.bintray.com/boostorg/master/ ] Also, if we were to delay the boost release until May, then what would happen to the August release? The release process for 1.71.0 is scheduled to start at the end of June. -- Marshall

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(no subject)
by Marshall Clow 13 Mar '19

13 Mar '19

Boost release 1.70.0 beta 1 is now available at: <https://dl.bintray.com/boostorg/beta/1.70.0.beta1/source/> The SHA256 checksums are as follows: dbf89645e509acb2e53eac3c633834f1dec80bd8622e6e652a9741dcf0807f17 ./boost_1_70_0_b1.7z 957b984b58656a3ec00661ecad7ef82e3a094bad36e37b9e6624843237854679 ./boost_1_70_0_b1.tar.bz2 76d149c1fb9e8a5ceb3bc1e5587edc40fa79a43e8b990d877c2210f0382b9421 ./boost_1_70_0_b1.tar.gz 71e990b2c26880521fd98459b184ee172ce1c46dcf554b6eaab7776b8b6369a6 ./boost_1_70_0_b1.zip For details of what's in the release, see < https://www.boost.org/users/history/version_1_70_0.html>. Please download the beta, give it a try, and report any problems you encounter. Thanks, -- The Boost Release Team

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Issue with boost::geometry::intersection
by Heriberto Delgado 13 Mar '19

13 Mar '19

I'm having an issue while using boost::geometry to find the intersection of two specific polygons, and looking at the evidence in front of me I can't help but think this might be a bug in the library. The two polygons in question are: POLYGON((16.8739 0.353458,8.80872e-14 5.50545e-15,0.266003 -12.6988,17.1399 -12.3454,16.8739 0.353458)) POLYGON((-4.53257e-19 2.16383e-17,9.99781 0.209424,10.1459 -6.86009,0.148086 -7.06952,-4.53257e-19 2.16383e-17)) Both of them look like two slightly rotated rectangles, first one being bigger than the other. They intersect at their upper left corner. In order to verify that these polygons CAN be intersected, I ran the following SQL sentence through SQL Server Management Studio (17.9.1): SELECT geometry::STGeomFromText('POLYGON((16.8739 0.353458,8.80872e-14 5.50545e-15,0.266003 -12.6988,17.1399 -12.3454,16.8739 0.353458))', 0) .STIntersection( geometry::STGeomFromText('POLYGON((-4.53257e-19 2.16383e-17,9.99781 0.209424,10.1459 -6.86009,0.148086 -7.06952,-4.53257e-19 2.16383e-17))', 0) ).STAsText() The resulting WKT is: POLYGON ((0.1480860710144043 -7.0695199966430664, 10.145899772644043 -6.8600900173187256, 9.997809886932373 0.20942401885986328, 0 0, 0.1480860710144043 -7.0695199966430664)) which looks about right for the requested intersection rectangle. SSMS itself displays a nice rectangle when you remove ".STAsText()" from that sentence. However, when I tried to duplicate that result using the following program using Visual Studio 2017 (15.9.8) to create an x64 console app, using boost 1.69 as a NuGet: ----------------------------------------------------------------------------------------------------------------- #include <boost/geometry.hpp> #include <vector> #include <iostream> int main(int argc, char** argv) { boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double>> first; boost::geometry::read_wkt("POLYGON((16.8739 0.353458,8.80872e-14 5.50545e-15,0.266003 -12.6988,17.1399 -12.3454,16.8739 0.353458))", first); boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double>> second; boost::geometry::read_wkt("POLYGON((-4.53257e-19 2.16383e-17,9.99781 0.209424,10.1459 -6.86009,0.148086 -7.06952,-4.53257e-19 2.16383e-17))", second); std::vector<boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double>>> results; boost::geometry::intersection(first, second, results); for (auto& result : results) { std::cout << boost::geometry::wkt(result) << std::endl; std::cout << boost::geometry::is_valid(result) << std::endl; } return 0; } ----------------------------------------------------------------------------------------------------------------- the resulting polygon is: POLYGON((0 -8.88178e-16,0.148086 -7.06952,0.148086 -7.06952,0 -8.88178e-16)) which you can easily see it's not a valid polygon, even though boost::geometry returns "1" when is_valid() is called upon it. I was planning to use boost::geometry on a large scale server application that processes quite large amounts of geometry in a similar way, and this is seriously impairing my ability to do so. Do you guys know what is going on here, and if there is a solution or workaround for it?

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