January 2024 - Boost - lists.boost.org

Review of proposed CharConv
by Antony Polukhin 25 Jan '24

25 Jan '24

## What is your evaluation of the design? Design follows the C++ Standard library design with all the latest additions. Everything is fine. ## What is your evaluation of the implementation? Fine in general. A few nitpicks/concerns follow. ### Arrays of constants RYU/fast_float/... are used for some of the conversions and most of those algorithms have huge tables full of constants. For example https://github.com/cppalliance/charconv/blob/41a83261c0f65aee575e89ccb71d94… and https://github.com/cppalliance/charconv/blob/41a83261c0f65aee575e89ccb71d94… and https://github.com/cppalliance/charconv/blob/41a83261c0f65aee575e89ccb71d94… Those constants have internal linkage. They are put in every translation unit that includes and uses them. Those constants would not be merged by linker. Moreover, the same constants with different names now exist in Standard Library implementations and are not merged with Boost.Charconv. To reduce the binary size and improve data locality I'd recommend switching to std implementation in sources if the feature test macro tells that std::to_chars/std::from_chars are fine. ### Internal headers in include/ Some of the headers are used only internally during build. It seems reasonable to move them to the src/ directory to make sure that no one uses them and that the library itself does not include them by accident. ### Header only support There is a PR to make the library header only https://github.com/cppalliance/charconv/pull/138 This feature is demanded by users however it raises the constants question again. Marking arrays of constants with `inline` should be done to make the constants externally visible, so that the linker could merge them. ### Constexpr for floats Just a feature request - it would be nice to have constexpr from_chars and constexpr to_chars for floating point types. If is_constant_evaluated() - do slow but constexpr conversion. Otherwise - fallback to std:: version or to the implementation in src/ ### Locales Locales are used in some corner cases along with switching them back and forth https://github.com/cppalliance/charconv/blob/41a83261c0f65aee575e89ccb71d94… Looks like there's no need in that line for locales switching. Just get the decimal point separator from the current locale and if it is not '.' then do the replacement of the first '.' to the locale's separator. ### Nitpicks Looks like zero initialization of the buffers could be skipped in following places: * https://github.com/cppalliance/charconv/blob/41a83261c0f65aee575e89ccb71d94… * https://github.com/cppalliance/charconv/blob/41a83261c0f65aee575e89ccb71d94… * https://github.com/cppalliance/charconv/blob/41a83261c0f65aee575e89ccb71d94… ## What is your evaluation of the documentation? Looks like parts of the docs repeat themself. For example, the reference section duplicates some of the previous descriptions. The latter could be just removed. Another thing that catches an eye are the benchmarks. Please also provide some absolute numbers because "X is five times faster than Y" could easily be that X and Y execute for ~1ns each. Those numbers are profitable for users. Side Note for myself: Seems that LexicalCast shows poor performance in some cases where it should not. Will investigate. ## What is your evaluation of the potential usefulness of the library? Very useful for libraries that wish to support pre-C++17 standards or a wide range of compilers. Useful for experimenting and prototyping new C++ Standard Library proposals ## Did you try to use the library? With what compiler? Did you have any problems? ## How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? Just looked through the code and the docs. ## Are you knowledgeable about the problem domain? I'm maintaining the Boost.LexicalCast and implemented a bunch of optimizations for std::to_chars/std::from_chars for the libstdc++. I'm not knowledgeable of RUY internals, but have the general understanding of the <charconv>. ## Do you think the library should be accepted as a Boost library? Yes

3 2

Zach Laine CharConv review
by Zach Laine 25 Jan '24

25 Jan '24

- What is your evaluation of the design? It follows the design of the equivalent facility in std::, so this feels moot. No complaints with that part. My only complaint is that the semantics of boost::charconv::from_chars and boost::charconv::from_chars_strict seem backward to me. I know this was mentioned by other reviewers. I think that with near-identity to the standard version, having the same (or corresponding name within boost::) should imply the same semantics. This is classic adherence to The Principle of Least Surprise. I would much prefer that the varying version have the different name, and that the one with the standard's semantics should be from_chars. I also encourage the authors to track any changes to std::from_chars with boost::charconv::from_chars. - What is your evaluation of the implementation? I mean, there's a lot of it. I'm sure it's all necessary, but I only looked at about 10% of it. What I saw seemed reasonable and well organized. - What is your evaluation of the documentation? It's great. The library is smallish, and the docs are correspondingly bite-sized, with plenty of examples. I might add a little more front matter that explains why someone should use this library. The docs get there, but putting it in the first paragraph is better. Busy people will blow right past everything that isn't in the first paragraph or two. - What is your evaluation of the potential usefulness of the library? High. I think the fact that this is a C++17 feature that we still can't reliably use says it all. The fact that it's about the same as the std:: implementation, or sometimes a little faster, is even better. - Did you try to use the library? With what compiler? Did you have any problems? Yes. I tried it with GCC 12, in a small test program just to see it go. No issues. - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? I spent about 3 hours, mostly looking at code. I also read all the docs and gave it a quick try. - Are you knowledgeable about the problem domain? Not particularly. I have written lots and lots of parsers, but never a simple low-level one like those in charconv. Zach

3 3

Review of Parser library scheduled
by Mateusz Loskot 17 Jan '24

17 Jan '24

Folk, Review of Zach Laine's Praser library has been scheduled [1] for February 19, 2024 - February 28, 2024 Big thanks to Marshall Clow for volunteering to be the review manager. [1] https://www.boost.org/community/review_schedule.html Best regards, -- Mateusz Loskot on behalf of Boost Review Wizards

1 0

Making Boost modular. IMPORTANT! URGENT! <insert-superlative-here>!
by René Ferdinand Rivera Morell 17 Jan '24

17 Jan '24

Dear fellow Boost authors, As some of you may have heard.. Some of us have been working on making it possible to fully consume Boost in a modular arrangement. First some FAQs about this: Q: What is a "modular arrangement"? A: It's when the libraries can be used, and hence built, without creating the monolithic headers, without needing the root build files, and without needing the libraries to be arranged in the usual root/libs/<name>. Q: Will a modular Boost remove the Boost release? A: No. The collection of libraries is still a single release. See recent discussions about this. Q: Will this change the testing? A: No, unless you want to. You will still be able to test the same non-modular way. But you could also test the modular way. Q: Will this require that we change the current Boost source structure? A: Yes. Unfortunately there is one restriction that adhering to a modular Boost requires. We would not allow sublibs. That is, that we can't support having libraries in root/libs/thing/<library> style locations. All libraries must be single libraries under the root/libs directory. Thankfully there's only a handful of such libraries. The root/libs/numeric/* group of libraries. Q: Why do we want a modular Boost? A: I'm not going to enumerate the reasons here. But let me just say.. That we've wanted a way to reduce, i.e. modularize, Boost since at least 19 years ago. When we added the "--without-<library>" build option to the root build file <https://github.com/boostorg/boost/blame/master/Jamroot#L107>. Now the work part.. Over the past year or so I've been making patches to the Boost build files, in my own repo, that cleans up the many, many, problems that make libraries depend on the current source structure. I've also made changes to B2 to make it easier/possible/automatic to deal with the new modular freedom. The B2 changes were naturally easy to put in since I control the repo and distribution. And the last bit of them shipped with the 1.83 release last Summer. But now I need to start pushing the changes to the many Boost repos to get this finished. A couple of weeks ago I started posting PRs to incrementally, and unobtrusively, make the changes to the Jamfiles. So far I have these: <https://github.com/boostorg/ublas/pull/189> <https://github.com/boostorg/interval/pull/38> I'm not sure how else to say this so.. PLEASE, PLEASE, merge those and future PRs ASAP. -- -- René Ferdinand Rivera Morell -- Don't Assume Anything -- No Supone Nada -- Robot Dreams - http://robot-dreams.net

7 12

Boost downloads and JFrog
by Glen Fernandes 13 Jan '24

13 Jan '24

Rather than emails and Slack DMs, I would prefer we have this discussion on the mailing list. To summarize what I have repeated in the aforementioned channels: - Yes, our downloads are not working again because the JFrog account is again not active. - No, I cannot do anything about the JFrog account. - Yes, we can update the website to point to downloads hosted elsewhere. It is correct that JFrog does not charge us yet but our traffic has increased from 60TB/month to almost 200TB/month which is no longer supportable for free. We have limited time to find a solution. We are on borrowed time but as far as I know we still have time. the deactivation of the JFrog account in December 31 was not expected, and it was reinstated. Glen

12 39

Request for comments: to_static_string
by Ruben Perez 13 Jan '24

13 Jan '24

Hi all, Since we will be reviewing Boost.CharConv shortly, and my development efforts in Boost.MySQL are currently requiring converting numbers to strings, I've been playing with the utilities we currently have to do so. I've found cases where I just needed to convert something to string, then pass the result to another function taking a string_view as parameter. The most efficient and correct way to do so is using to_chars (stack based, non-throwing, C++23 constexpr and locale-independent). But I still like the simplicity of std::to_string. Since I had some free time this weekend, I took a step forward and implemented a (deadly simple) wrapper around to_chars that looks like std::to_string, but has all the benefits of to_chars. I called this to_static_string. Repo is here: https://github.com/anarthal/to-static-string This is currently a prototype. I want to hear everyone's opinion on this - do you think this may be useful to any of you? I don't think it's big enough to even consider putting it into Boost (my idea is having it as a standalone lib). Any comments are welcome. Thanks, Ruben.

2 3

[scope] Some random thoughts
by Andrzej Krzemienski 10 Jan '24

10 Jan '24

Hi All, Two observations from reading the docs. Why do I need a condition in scope_exit when I have a scope_fail? I recommend putting warning somewhere in the docs that while using scope guards you may inadvertently read an object after move: std::string checked(std::string name) { scope::scope_exit g{[&]{ std::clog << "checked " << name <<std::endl; }}; validate(name); return name; // name becomes moved-from } Regards, &rzej;

3 5

Forthcoming Boost.Charconv review January 15th - 25th, 2024
by Christopher Kormanyos 09 Jan '24

09 Jan '24

Dear all, The review of Boost.Charconv by Matt Borland is scheduledfrom Monday, January 15th to January 25th, 2024. ----------------------------------------------------- About the library: Boost.Charconv provides a highly portable and efficient, C++11 implementation of <charconv>. The API containsfunctions compatible with <charconv>. Boost.Charconv can be highly useful for portability and efficiency. The standard library's <charconv> requires C++17 or higher. Currently only quite modern compilers such as GCC 11+ and MSVC 19.24+ support both integer and floating-point conversions in their implementation of <charconv>. If you are using either of those compilers, Boost.Charconv is at least as performant as <charconv>, and can be up to several times faster. If you are using an older compiler or a language standard lower than C++17, then there is no <charconv> available. In such cases, Boost.Charconv provides a highly-viable, portable and efficient header-only implementation. Boost.Charconv is a compiled library and does require a few other Boost libraries to run. The docs providedirections for how to consume with b2, vcpkg and Conanto facilitate this. Boost.Charconv fits into Boost stylistically and through itshigh quality, its Boost-like testing and its documentation. Boost.Charconv has been well-received and endorsed on the Boost-lists and is already being used for prototyping in several existing Boost libraries. Tool vendors have expressed interest in Boost.Charconv particularly due to its high performance and clarity of implementation details. docs: https://develop.charconv.cpp.al git: https://github.com/cppalliance/charconv --------------------------------------------------- Naturally, you need not wait until the review formally opens to start reviewing the Charconv library. Please always state in your review whether you think the library should be accepted as a Boost library! Please consider giving feedback on the following general topics: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? Christopher Kormanyos Boost.Charconv Review Manager ------------------------------

2 2

boost.sqlite
by Klemens Morgenstern 06 Jan '24

06 Jan '24

I've written a boost.sqlite library last year mainly to experiment, but it has been a feature-complete C++ wrapper for a while. Hence I'd like to gauge interest to see if it's worth proposing for boost. It has more features than most C++ sqlite wrappers and uses boost-isms such as system.result, tag_invoke and boost.json. Code: https://github.com/klemens-morgenstern/sqlite Docs: https://klemens.dev/sqlite/

5 9

Re: [boost] Interest in new parsing library?
by tobi＠die-loews.de 06 Jan '24

06 Jan '24

Zach Laine wrote: > - use approximately the same set of directives to influence the parse > (e.g. lexeme[]); It seems there is no directive like Spirit's no_case. Is there a way to match case-insensitivity?

2 2