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[OpenMethod] Few questions about unreasonable effectiveness of fast_perfect_hash and other minor things
by Ivan Matek 02 May '25

02 May '25

Hi everyone, few questions: 1. fast_perfect_hash achieves performance(load factor) I would assume is impossible, based on perfect hashing talk <https://www.youtube.com/watch?v=yOo6GnbKzp8>. I presume reason why it works so well that compiler places type info data clustered in same region of addresses... Is that correct? 2. regarding static_list: would Boost.Intrusive list work here also, and if so was this considered? 3. basic_error_output does not seem to need the Policy template parameter, is this left for consistency or am I wrong that it is not needed? 4. dynamic_cast_ref docs <https://github.com/jll63/Boost.OpenMethod/blob/ea7dbe86b511797f0281ef07b3ad…> mention that D must match the reference category of B. Would it be possible to static_assert that?

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[OpenMethod] Questions about custom policies.
by Ivan Matek 01 May '25

01 May '25

Hello, I just started with review and I have a cluster of questions, but it is not clear what the root cause of my issues is so apologies if ordering of questions is wrong. 1. I wanted to get hash map stats, but they are not printed in debug policy, even when env variable is set, I must hack release policy like this: - vptr_vector<release>, vectored_error_handler<release>> {}; + vptr_vector<release>, vectored_error_handler<release>, basic_trace_output<release>> {} Is this expected? IDK why debug prints some trace, but not hash info 2. While playing with this I get crashes when I just c/p release policy and rename it, e.g. +struct my_release : basic_policy< + my_release, std_rtti, fast_perfect_hash<my_release>, + vptr_vector<my_release>, vectored_error_handler<my_release>> {}; crashes in template<bool Indirect> inline auto box_vptr(const vptr_type& vp) { if constexpr (Indirect) { return &vp; } else { return vp; } } but when I switch boost::openmethod::initialize<boost::openmethod::policies::my_release>(); to boost::openmethod::initialize<boost::openmethod::policies::release>(); it works fine. It also exibits some other weird behavior, e.g. if I switch debug inheritance from release to my_release crash goes away, even when not using debug... Looks to me I am doing something that is not allowed, but it is not clear what I am doing wrong. regards, Ivan

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[OpenMethod] Some questions
by Andrzej Krzemienski 30 Apr '25

30 Apr '25

Hi Everyone, I have concerns with the design philosophy of OpenMethod library. Giving this flexibility that one person can add new open methods to a class hierarchy in one file and another person can add classes to a class hierarchy in another file independently, this is asking for miscommunication problems (programmer bugs) discovered only at runtime. I tried to recreate this situation that I expect would be common. My first question, even before I run tests is what will happen when I have a class hierarchy: struct Node { virtual ~Node(); }; struct XNode : Node {}; I declare an open method `value()` and override it for XNode in one file, adn in another file I extend the hierarchy with: struct YNode : Node {}; And then in main(), in yet another file, I will call `value()` with `YNode`. The documentation does not give me a clear answer. Section Error Handling says, > When an error is encountered, the program is terminated by a call to abort. And then in the next sentence it talks about different debug and release policies, and ultimately, I do not know if by default abort() is called or not. But that is not the only problem. The docs use the term " When an error is encountered". What is considered "an error" here? How many situations constitute "an error"? The docs should enumerate all these situations. I need to know when my program will be calling `abort()`. So, I dun a Compiler Explorer test: https://godbolt.org/z/3fW8j4eTM And indeed, I get something that looks like abort() But when I wrap the call into a try-catch block, all of a sudden, the implementation seems to pick the wrong overrider and return a value, clearly not the intended one. And the program goes on: https://godbolt.org/z/Y6z3o56h5 This is the worst thing that can happen: a random runtime behavior. Is this a bug? Or am I missing something? Next question that naturally arises: how do I declare `noexcept` open methods with this library? Regards, &rzej;

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Proposal: Abandoning monolithic Boost documentation.
by René Ferdinand Rivera Morell 23 Apr '25

23 Apr '25

Today, in slack, we had a discussion on problems with building the monolithic docs. For context what I'm calling the monolithic docs are these <https://www.boost.org/doc/libs/1_88_0/doc/html/libraries.html>. The main problem that was raised is that a failure in one library causes all the docs to disappear. That problem is due to the nature of DocBook, XSLT, and the single monolithic generation. This is not something that can be resolved at the build system leve. The one solution is to abandon the monolithic build. And instead move to only having per library documentation builds. Hence.. I am proposing we abandon the monolithic documentation build. The benefits: * No longer missing docs from problems in individual libraries. * It's modular. I.e. libraries would build, and include, their docs in the modular layout. Do note that most libraries, more than 2/3, already use modular documentation. So technically this would be completing the modular transition that has already been happening. Thoughts? -- -- René Ferdinand Rivera Morell -- Don't Assume Anything -- No Supongas Nada -- Robot Dreams - http://robot-dreams.net

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Review Manager Volunteers
by Matt Borland 23 Apr '25

23 Apr '25

Hi All, Recently, we've seen a shortage of review managers: Joaquin has been looking for one for his bloom-filters library for a few weeks (now solved), and Dmitry recently withdrew his GDB debugging tools due to lack of review manager. Looking at the review schedule for the last few years[1] you'll find a number of repeated names and long-time contributors. In an effort to find new volunteers for review managers I would like to ask what are the showstoppers that keep you from wanting to be a review manager? Time, Training, Recognition, none of the above? I am genuinely curious in an effort to find new volunteers so we can continue to add great libraries to the project. Thank you, and Happy Easter to those that celebrate. Matt [1] https://www.boost.org/community/review_schedule.html

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Printf library suggestion
by Aaron Graham 22 Apr '25

22 Apr '25

I'd like to gauge the interest in adding the following library to boost: https://github.com/rokudev/rostd/blob/main/include/rostd/printx.hpp It's a simple library that checks and rewrites the format string at compile time in order to fortify it for use with printf, leaving the object code with only a call to the underlying C-standard printf-family function. It's a single header and requires C++20 or above (for cNTTP support). It contains these four functions: printf, sprintf, snprintf, fprintf These functions are used like so: printf<"Hello %s\n">("World!"); char buf[20]; sprintf<"Hello %s\n">(buf, "World!"); // yes, it's safe char buf[20]; snprintf<"Hello %s\n">(buf, sizeof buf, "World!"); fprintf<"Hello %s\n">(file, "World!"); Features/rationale: * It provides old-style printf (supports all standard printf specifiers). * Fully type-safe. No format string attacks. Issues are found at compile time. * Length modifiers are deduced; these format strings are portable. (No PRIu64 inttypes stuff needed anymore, just use %u) * Adds %? format specifier (print whatever type is there). * Compiles to std::printf (much smaller object code than std::format). * Provides a way for developers to easily adapt this printf formatting capability to their own functions (logging, etc.) More detailed rationale is here: https://github.com/rokudev/rostd/blob/main/doc/printx.adoc

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Unable to migrate from Oracle Linux 8 to Oracle Linux 9 due to Boost dependency
by Pavithra Raghavendran 22 Apr '25

22 Apr '25

Hi Team We are writing this mail requesting your assistance for boost related issue which we are facing while migrating from Oracle Linux 8 (OL8) to Oracle Linux 9 (OL9) OS. Issue Description: When we try to upgrade the OS from OL8 to OL9, we are seeing errors related to boost version 1.66.0 and the RPM which was already successfully installed on OL8 is getting removed. Note: On OL8 OS, the available version of boost from yum is boost-1.66.0 & on OL9 OS, the available version of boost from yum is boost-1.75.0. Brief: Our application RPM is compiled on an OL8 machine(development machine) and is dependent on boost library (linked dynamically). When we install this RPM on another OL8 machine(test machine), the RPM installation is successful. This is because the boost version in our RPM and the test OL8 machine matches i.e. both require boost-1.66.0. However, when we upgrade the OS from OL8 to OL9, the application RPM is getting removed with the errors as shown below. This is because OL9 has boost-1.75.0 libraries but our RPM has boost libraries which is dynamically linked with boost-1.66.0. [root@vm227-66-vm5 ~]# dnf install ocsm-6.0.0.0.0-608.x86_64.rpm Last metadata expiration check: 0:13:25 ago on Tue 25 Mar 2025 12:25:18 PM CET. Error: Problem: conflicting requests - nothing provides libboost_filesystem.so.1.66.0()(64bit) needed by ocsm-6.0.0.0.0-608.x86_64 from @commandline - nothing provides libboost_program_options.so.1.66.0()(64bit) needed by ocsm-6.0.0.0.0-608.x86_64 from @commandline - nothing provides libboost_regex.so.1.66.0()(64bit) needed by ocsm-6.0.0.0.0-608.x86_64 from @commandline - nothing provides libboost_system.so.1.66.0()(64bit) needed by ocsm-6.0.0.0.0-608.x86_64 from @commandline Analysis: To simulate this above scenario, we have written a very simple sample program using the boost library and compiled the code on OL8 OS and linked dynamically with boost version 1.66.0. Once RPM is ready, we installed it on an OL8 virtual machine. Installation is successful because our compiled RPM has boost-1.66.0 libraries(libboost_program_options.so.1.66.0) and OL8 supported version of boost is also 1.66.0. Now, when we upgrade the OS from OL8 to OL9, the default boost available on OL9 is boost-1.75.0, and since our RPM is linked with boost-1.66.0 libraries, installation is failing with the below errors (similar to the application errors mentioned in Brief section). [root@localhost ~]# sudo dnf install boost_demo-1.0.0-1.el8.x86_64.rpm Last metadata expiration check: 0:23:05 ago on Mon 21 Apr 2025 01:00:57 PM CEST. Error: Problem: conflicting requests - nothing provides libboost_program_options.so.1.66.0()(64bit) needed by boost_demo-1.0.0-1.el8.x86_64 from @commandline - nothing provides libboost_system.so.1.66.0()(64bit) needed by boost_demo-1.0.0-1.el8.x86_64 from @commandlin In our application, we have not linked to any specific version of boost dependency i.e. we have nowhere mentioned the version of boost to be used as 1.66.0. Since OL8 yum repo has boost-1.66.0, our application is considering version 1.66.0 while building RPM. However, while migrating from OL8 to OL9 we are seeing the above-mentioned issue and hence we are unable to complete the upgradation process which is crucial to our customers. Query: Can you please let us know how we can ensure that the OS gets upgraded from OL8 to OL9, without application RPM(linked dynamically to boost-.1.66.0) being removed. Thanks Pavithra

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[bloom] Review Announcement: Boost.Bloom (May 13-22, 2025)
by Arnaud Becheler 21 Apr '25

21 Apr '25

Dear Boost community, The review of the Boost.Bloom library begins on May 13th, 2025, and will run through May 22nd, 2025. Boost.Bloom is a header-only C++ library written by Joaquín M López Muñoz, providing fast and flexible Bloom filters. These are space-efficient probabilistic data structures used to test set membership with a controllable false positive rate and minimal memory footprint. The library supports a variety of configurations and hash policies and is designed to integrate well with modern C++. You can find the library here: - Repo: https://github.com/joaquintides/bloom - Documentation: https://master.bloom.cpp.al/ Bloom filters are especially useful when: - You need to test if something is not in a large dataset, and can tolerate a small false positive rate. (e.g., avoiding duplicate URL crawls in a web crawler) - You need a memory-efficient structure to represent large sets (e.g., checking for the presence of DNA subsequences across massive genomic datasets) - You want to avoid expensive lookups for items that are definitely not present (e.g., filtering nonexistent records before querying a remote database). As always, we welcome all reviews — from quick impressions to detailed analysis. Your feedback helps ensure that the library meets Boost's high standards in terms of correctness, performance, documentation, and design. If you’re interested in contributing a review, please post to the Boost mailing list during the review period. Note: All links to other parts of Boost in the Boost.Bloom documentation are currently broken, as they were written with the assumption that the library was already integrated into Boost - please do not account for those in your review. Thank you in advance for your time and insights! Best regards, Arnaud Becheler Review Manager, Boost.Bloom

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Boost v1.88 Release Report
by Robert Beeston 18 Apr '25

18 Apr '25

The release report for v1.88 is now available, now packed with even more information including mailing list, slack, git commits and other statistical information that happened on the path to the current release. https://downloads.cppalliance.org/reports/boost_1_88_0_release_report.pdf *Rob Beeston* Creative Director C++ Alliance cppalliance.org

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[bloom] Looking for a review manager for candidate Boost.Bloom
by Joaquin M López Muñoz 18 Apr '25

18 Apr '25

Candidate Boost.Bloom has been endorsed by members of the community, so I'd like to proceed with the official review and for that a volunteer is needed to act as the Review Manager: Repo: https://github.com/joaquintides/bloom Docs: https://master.bloom.cpp.al/ These are the general requisites and assigned tasks for the Review Manager: https://www.boost.org/community/reviews.html#Review_Manager If you're interested, please respond to this post and/or contact me privately. Thank you! Joaquin M Lopez Munoz

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