September 2018 - Boost - lists.preview.boost.org

[asio][coroutine] forbid_suspend blocks
by Vinícius dos Santos Oliveira 07 Aug '19

07 Aug '19

I've implemented a dumb linter using Python + clang API that allows you to mark certain blocks as “atomic in respect to coroutines” using C++11 attributes. Usage example follows: void f() { int yield; g(yield); [[bt::forbid_suspend]] { // Comment this call to make linter accept the code g(yield); t(); } } You can change bt::forbid_suspend to another identifier by tuning settings on the beginning of the script. The prefix forbid was inspired by Rust's linters[1] as you cannot disallow the linter from inside the forbid_suspend block. Some limitations follow: - A suspend point is identified by looking references to any id equals to yield in the last argument passed to function calls. It means that yield[ignored_ec] and alike will be correctly identified, but it needs to be named yield and it needs to be the last argument to the function call. - I haven't found a way to extract attributes related to COMPOUND_STMT nodes with clang API, so I manually look for token gaps and do a simple regex. It means you cannot use macros to [[bt::forbid_suspend]] as the macro won't be expanded. - You better call the script with '-x c++' and also ' -I/usr/lib/clang/5.0.1/include'. Like I've said in the beginning of the email, it's a *dumb* linter, which means it doesn't try to handle all cases. Therefore, I don't hope to do many changes to it or maintain it to work against newer releases of clang and I'm only uploading it to gist (not fullblow Github): < https://gist.github.com/vinipsmaker2/d930fbe5b7597432b021effe618da171>. It should also be easy to hack as it is very small. I'm releasing the linter under public domain. Enjoy. I have been using fibers in a daily basis on the last months of my job to solve networking problems on a gateway project. Some of the technologies I use are: - Boost.Asio and its spawn function. - A few custom synchronization primitives for the fibers (e.g. mutex, semaphore). - Eventually I'll have to write a custom spawn function that returns a joinable handle so I can kill the usage of a fiber::barrier in a few places. I've been using the linter for about a week already and looks fine. My use case are: - To prevent iterator invalidation in regions accessing shared variables. - To guarantee events order in algorithms that handle races (cannot yield while task YYY hasn't finished). The project I use it in is not an open source project, so I cannot talk much more about it. Also, I don't claim my solution is original. I wouldn't be surprised if the very same solution exists in the wild (please let me know if you know of a similar approach). This is not a new problem. It is know for some time. For instance, in P0171, Gor Nishanov noted this same problem: “In coroutines the suspend point is clearly marked with await, which tells the reader that something unusual happens in this function and allows the reader, for example, to confirm whether the lifetimes of the objects of interest align with the lifetime of the coroutine or not, whether some locks need to be acquired to protect some concurrently accessed data, and whether some locks need to be released before the execution reaches the suspend point.” — <http://open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0171r0.html>, 2015 However, the solution he presented was to manually examine whole blocks of code without help from the compiler. I argue that the solution he presented is as error-prone as manually looking for exit paths that don't free acquired resources in languages lacking RAII. And I've been spoiled too much by RAII. Furthermore, I take this comment of his with highly suspicious look: “Since we are on the subject of maintenance nightmares, we would like to offer a conjecture that the absence of the await in P0114 is a likely source of many maintenance nightmares. Without a syntactic marker to signal to the person reading the code that something funny is going on, it is impossible to tell whether the following code is correct or not” — http://open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0171r0.html If I had to give a vote to the proposal he was defending or Chris' proposal, I'd probably have chosen Chris'. [1] https://doc.rust-lang.org/reference/attributes.html# lint-check-attributes -- Vinícius dos Santos Oliveira https://vinipsmaker.github.io/

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Re: [boost] [ Interest? ] [ out_ptr ] Tiny C++ Abstraction for C-Style Output Pointers
by Bjorn Reese 12 May '19

12 May '19

On 06/28/18 21:03, ThePhD via Boost wrote: > out_ptr is a small abstraction for making types such as > std::unique_ptr, std::shared_ptr, boost::shared_ptr, and the upcoming > std::retain_ptr > <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0468r0.html> work > work C-Style output functions as a parameter, addressing the need of > wanting to be able to do "my_c_api_init( foo, bar, &my_smart_ptr );". It's Does out_ptr have other use-cases than C interoperability?

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[test] unit test command-line handling
by Stefan Seefeld 22 Mar '19

22 Mar '19

Hello, this is a question concerning the Boost.Test framework. I'd like to pass command-line arguments to my tests, and I'm unsure of how to proceed. I have found https://www.boost.org/doc/libs/1_68_0/libs/test/doc/html/boost_test/adv_sce…, which shows how to access the command-line programmatically, but that's declared obsolete, and it's also lacking some important info, such as how I should handle the argv vector. Are there any examples that demonstrate this use case ? Specifically: * What (non-deprecated) API can I use to access command-line arguments during test initialization ? * How does my own handling of command-line arguments interact with Boost.Test's own command-line argument handling ? Thanks, Stefan -- ...ich hab' noch einen Koffer in Berlin...

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clang-win, again
by Peter Dimov 31 Oct '18

31 Oct '18

Has anyone succeeded in getting clang-cl.exe working under b2? I've installed llvm-6.0.1, added it to PATH, put using clang-win : : : <compatibility>vc14 ; in my user-config, and what I get is: C:\boost-git\develop\libs\smart_ptr\test>b2 toolset=clang-win sp_interlocked_test warning: mismatched versions of Boost.Build engine and core warning: Boost.Build engine (b2) is 2015.07.00 warning: Boost.Build core (at C:/boost-git/develop/tools/build/src) is 2018.02-git C:/boost-git/develop/tools/build/src/tools\msvc.jam:1087: in set-setup-command *** argument error * rule virtual-target.from-file ( file : file-loc : project ) * called with: ( : /C:/boost-git/develop/libs/smart_ptr/test : object(project-t arget)@129 ) * missing argument file C:/boost-git/develop/tools/build/src/build\virtual-target.jam:970:see definition of rule 'virtual-target.from-file' being called C:/boost-git/develop/tools/build/src/tools\msvc.jam:652: in clang-win.compile.c+ + C:/boost-git/develop/tools/build/src/kernel\modules.jam:107: in modules.call-in C:/boost-git/develop/tools/build/src/util\indirect.jam:105: in indirect.call C:/boost-git/develop/tools/build/src/build\virtual-target.jam:902: in execute C:/boost-git/develop/tools/build/src/build\virtual-target.jam:821: in class@acti on.actualize C:/boost-git/develop/tools/build/src/build\virtual-target.jam:332: in actualize- action C:/boost-git/develop/tools/build/src/build\virtual-target.jam:518: in actualize- no-scanner C:/boost-git/develop/tools/build/src/build\virtual-target.jam:142: in class@virt ual-target.actualize C:/boost-git/develop/tools/build/src/build\configure.jam:258: in try-find-build C:/boost-git/develop/tools/build/src/build\configure.jam:396: in find-builds-raw C:/boost-git/develop/tools/build/src/build\configure.jam:455: in configure.find- builds C:/boost-git/develop\boostcpp.jam:734: in boostcpp.deduce-address-model C:/boost-git/develop/tools/build/src/kernel\modules.jam:107: in modules.call-in C:/boost-git/develop/tools/build/src/util\indirect.jam:105: in indirect.call C:/boost-git/develop/tools/build/src/build\property.jam:144: in property.evaluat e-conditionals-in-context C:/boost-git/develop/tools/build/src/build\targets.jam:1087: in evaluate-require ments C:/boost-git/develop/tools/build/src/build\targets.jam:1121: in common-propertie s2 C:/boost-git/develop/tools/build/src/build\targets.jam:1017: in targets.common-p roperties C:/boost-git/develop/tools/build/src/build\targets.jam:1313: in class@basic-targ et.generate C:/boost-git/develop/tools/build/src/build\targets.jam:812: in generate-really C:/boost-git/develop/tools/build/src/build\targets.jam:784: in class@main-target .generate C:/boost-git/develop/tools/build/src\build-system.jam:797: in load C:\boost-git\develop\tools\build\src/kernel\modules.jam:295: in import C:\boost-git\develop\tools\build\src/kernel/bootstrap.jam:139: in boost-build C:\boost-git\develop\boost-build.jam:17: in module scope

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[test] How to execute shell commands
by Mike Dev 18 Oct '18

18 Oct '18

As an extension to my previous question: Does the boost test framework provide an integrated mechanism to get the binary directory (the directory where the currently running test executable is placed) and/or the source directory (where the jam-file resides that defined the test)? Best Mike

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[RFC] unique_val (handles, IDs, descriptors...)
by Miguel Ojeda 15 Oct '18

15 Oct '18

Hi all, While working on a medium-sized project, I had to wrap quite some handles, IDs, descriptors, etc. into RAII classes. Somehow, writing those and making them movable seemed more verbose than needed. I searched in the STL and Boost for something already implemented, but nothing seemed to come up. I decided to write my own prototype to see whether I was missing something important; but actually using it in my project felt quite natural and simple. At this point, I asked for a second opinion from a well-known expert (thanks Scott!) and he agreed that it seemed like a reasonable idea but, of course, he would also be surprised if others haven't come up with something similar. So I polished it up a bit and uploaded it to: https://github.com/ojeda/unique_val Below you have the introduction inlined [1]. If you have the time, please take a look (specially to the Rationale) and let me know your comments. The code itself is very short and straightforward. If you already have this class/template in Boost somewhere that I missed, please let me know! Otherwise, if you think this could be interesting to put into Boost in some existing library (not sure which) or as a new tiny library, I would be glad to make the effort to expand it, clean it up, etc. Thank you! Miguel [1] """ A single-header header-only library for representing unique values (handles, IDs, descriptors...) that default to a value on move for C++11, C++14 and C++17. It simplifies writing resource-owning classes (RAII) with move semantics support for resources with handles, IDs or descriptors that are supposed to be used as unique values, not as unique pointers. For instance, it can be used with non-pointer handlers (like the `int` file/socket descriptors in POSIX) and with opaque pointer handlers (like the `HWND` handles in the Win32 API). As such, it can be used as an alternative to `std::unique_ptr` with or without custom deleter, specially for resources that use a non-pointer type or resources that are not simply heap-allocated. It does not have any overhead compared to using the original type. It supports booleans, integers, pointers and enumerations. The default value can be different than the default-constructed value (i.e. different than 0, nullptr, etc.). """

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Boost xxhr ? High level http client library
by Damien Buhl 13 Oct '18

13 Oct '18

Dear Boost, I've built an header-only library based on Boost.Beast which allows you to perform HTTP requests. It is implememented with two backends : * Boost.Beast for native builds. * XmlHttpRequest for WebAssembly (plans to migrate to fetch API which is richer) Actually Boost.Beast is a great lib, however it's API is thought to build HTTP centric app not just to make some simple HTTP call ( as for example urdl was ). xxhr on the other hand is about making it simple to call an HTTP service. Usage example : GET <https://nxxm.github.io/xxhr/html/namespacexxhr.html#a69bafa24d7c33b004a7de8…>( "http://httpbin.org/anything"s, on_response = [](auto&& resp) { std::cout << resp.text; }); I would be really interested in a pre-review or some feedback about it's API. The implementation merits more attention and can significantly be improved but this email is to grab a first feedback from the community. Documentation : https://nxxm.github.io/xxhr/ GitHub : https://github.com/nxxm/xxhr Example code relying on it : nxxm/gh <https://github.com/nxxm/gh>: partial GitHub API implementation Thanks for your time :) -- Damien Buhl Software Developer +33 6 77 43 10 05 https://nxxm.github.io/

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Tools to manage multiple repositories effectively?
by James E. King III 09 Oct '18

09 Oct '18

Hello, I am looking for tools that would allow me to create a portal and/or monitor the following properties of boost repositories. I am in the CMT and at least one fix that was in develop never made it into master for the 1.68.0 release, so I want to be able to see, at a glance, information about the boost repositories I care about in one place. There are about 20 repositories I regularly participate in now so a portal to show what I need to worry about would be useful. 1. How far behind is master (with respect to develop)? This would help identify which repositories are behind develop. Useful for ensuring things get into a release. 2. How many open pull requests? 3. How many new pull requests (within the last week)? 4. How many updated pull requests (within the last week)? 5. How many open issues? 6. How many new issues (within the last week)? 7. How many updated issues (within the last week)? "week" could be configured, perhaps month, or "since I last visited". Anybody know of any good tools or perhaps an existing site that can do this for a multi-repository solution? Thanks, Jim

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Formal Review of Proposed Boost.Histogram Library is FINISHED
by Mateusz Loskot 05 Oct '18

05 Oct '18

Dear Boost Community, The formal review of Hans Dembinski's Histogram library has been completed. Here is the quantitative summary of feedback received: * Reviews: 1. Klemens David Morgenstern 2. Jim Pivarski (off-list via e-mail to Hans) 3. Björn Reese 4. Steven Watanabe 5. Alex Hagen-Zanker * Non-review participations: 1. degski 2. Gavin Lambert 3. Seth 4. Mateusz Loskot I believe I've collected the names/numbers right, but please let me know ASAP if you think otherwise. I'd like to thank all the participants for their time and efforts. I'm sure Hans received lots of valuable comments and suggestions. FYI, the discussion threads are still open for new posts. Those won't be taken into consideration towards the review result though. I will do my best to announce the review results next week. Mateusz Review Manager for the proposed Boost.Histogram -- Mateusz Loskot, http://mateusz.loskot.net

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Twenty years and time to retire
by Beman Dawes 04 Oct '18

04 Oct '18

The idea behind Boost was hatched in March, 1998, and the proposal document <https://www.boost.org/users/proposal.pdf> was released May 6, 1998. That makes Boost twenty years old, and makes me twenty years older. It is high time I retire from Boost; I haven't been able to contribute for some time now. Thanks to all of you who made Boost such an overwhelming success in the past and will drive Boost forward into a bright future! --Beman

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