- Boost-users - lists.boost.org

Re: [asio-users] boost::asio and seccomp
by Vinícius dos Santos Oliveira 17 Nov '25

17 Nov '25

Em seg., 17 de nov. de 2025 às 13:09, Marek Küthe <m-k-mailling-list(a)mk16.de> escreveu: > Hello, Hi Marek, I have lots of experience with containerization & sandboxing on Linux (and FreeBSD), but very few people to talk to about it (which I do miss more of). Let's keep in contact after I try to help answer your questions. > I would like to make my program more secure under Linux with seccomp. > My question is: how can I query which backend boost::asio uses (epoll, > select, etc.)? Boost.Asio doesn't have fallback logic. You choose which backend to use at compile time by defining macros. Given most vendors disable io_uring nowadays[1], the ideal implementation would not work as Boost.Asio does. The ideal implementation would have fallback logic and try io_uring first. This would also help with sandboxes because seccomp is a terrible model to secure io_uring in capability sandboxes (io_uring communicates with the kernel through message writes, but seccomp only filters syscalls). So if Boost.Asio had fallback logic your application would be able to fork the process, and disable io_uring. On the forked process, Boost.Asio could use epoll while the parent process would use io_uring. That's not possible today. Landlock is a promising new Linux approach that won't ever replace seccomp, but has the potential to secure some interfaces that seccomp can't. Until Landlock is mature and more complete, we have to do stuff such as avoiding io_uring entirely within sandboxes. For Boost.Asio this means using the epoll backend. > I would also like to know which system calls boost::asio > uses for which Linux backend. io_uring doesn't use syscalls so there's no point in filtering syscalls to secure io_uring. For the epoll backend, everyone does basically the same things. Just go through the list of syscalls and enable everything epoll-related. You can look at Kafel for an easy to use language to define seccomp policies. I wrote a few policy groups if you're interested. The only weird thing about Boost.Asio is that it still relies on the ancient'n'fragile FIONBIO[2] instead of fcntl/O_NONBLOCK by default (and MSG_DONTWAIT when available to save syscalls/performance). I complained to Chris until he fixed almost all of my complaints. Nowadays you can use Boost.Asio in many models of capability sandboxes, but not all. The only missing piece is MSG_DONTWAIT which matters to avoid DoS when file descriptors are shared among untrusted processes (necessary for capability sandboxes). I wrote a very detailed article explaining how to develop sandboxes for Linux and FreeBSD, but I suspect only 2 people have actually read the whole thing: https://blog.emilua.org/2025/01/12/software-sandboxing-basics/ The described model is implemented in Emilua which is a runtime (similar to NodeJS) for LuaJIT using Boost.Asio (you can also configure it to use the standalone version of ASIO if you want). Emilua is also a container runtime. You can prototype stuff quickly in Lua using Emilua and implement a high-performance version in pure C++ later if the need arises. That's the last demo I made for Emilua: https://www.youtube.com/watch?v=anu-onpDMBc I'm now keeping in contact with Matthew Flatt to implement sandboxes for Racket. However Racket doesn't use Boost.Asio. I'm also designing a thing to more easily implement sandboxes in C++, but it's still too soon to show this work. I've tried to collaborate with JS runtime developers to implement sandboxes too, but every time I've left these meetings frustrated. JS guys have no ambition at all. They only want to mirror what NodeJS already does (and perhaps do the same stuff but only slightly faster). I have no intention to collaborate with JS communities again. I want to collaborate with ambitious programmers who want to do more than what's possible today. I don't want to collaborate with programmers whose souls are already dead. > Can anyone help me with this? Is this documented anywhere? There's no documentation. I hope my attempts to explain seccomp, io_uring and Boost.Asio were useful to you. [1] https://security.googleblog.com/2023/06/learnings-from-kctf-vrps-42-linux.h… [2] https://stackoverflow.com/a/1151077/883113

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[release] Boost 1.90.0 beta 1 released
by Marshall Clow 14 Nov '25

14 Nov '25

Boost release 1.90.0 beta 1 is now available at: https://archives.boost.io/beta/1.90.0.beta1/source/ The SHA256 checksums are: 8072831c2c54c7e0e99c69e934b5694574565dd435de19a0a43f7bf7dabad71b boost_1_90_0_b1.zip d1754f544e83418c2b5fe18245666830088948cb3629d2b346d56f31c71138e5 boost_1_90_0_b1.tar.bz2 c94235eb00edc732253d3ae8000a489ffc5773f34cd98bd7645d54cb4ae2482a boost_1_90_0_b1.7z 0f55a646eaed4daf110eeec7c2c70e2c7058efa77eef31137248a6e2cf1412da boost_1_90_0_b1.tar.gz Please try the beta and report any problems you encounter. Thanks to everyone who contributed to the release. -- The release managers

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Using lambda or functor as match_condition with boost::asio::read_until()
by Klebsch, Mario 28 Oct '25

28 Oct '25

Hello, I want to use boost::asio::read_until() and pass a functor as match condition. But I don't get it to compile. Here is my source code: #include <boost/asio.hpp> using namespace boost::asio; using iterator = buffers_iterator<streambuf::const_buffers_type>; struct completion_functor { std::pair<iterator, bool> operator()(iterator begin, iterator end) { return {}; } }; completion_functor functor; static_assert(is_match_condition<completion_functor>::value, "completion_functor must be match condition"); static_assert(is_match_condition<decltype(functor)>::value, "functor must be match condition"); std::pair<iterator, bool> completion_func(iterator begin, iterator end) { return functor(begin, end); } static_assert(is_match_condition<decltype(completion_func)>::value, "completion_func must be match condition"); auto lambda = [](iterator begin, iterator end) -> std::pair<iterator, bool> { return {}; }; static_assert(is_match_condition<decltype(lambda)>::value, "lambda must be match condition"); std::pair<iterator, bool> completion_func2(iterator begin, iterator end) { return lambda(begin, end); } static_assert(is_match_condition<decltype(completion_func2)>::value, "completion_func2 must be match condition"); int main(int argc, char *argv[]) { io_context ctx; ip::tcp::socket s{ctx}; streambuf buffer; read_until(s, buffer, '\n'); read_until(s, buffer, completion_func); read_until(s, buffer, completion_func2); // the following calls do not compile // read_until(s, buffer, functor); // read_until(s, buffer, lambda); } It seems, that boost::asio::is_match_condition<> does neither accept my lammda-function nor my functor. The only completion handler, that I get accepted, is a classic, free-standing function (and static class member functions, too). But in that function, calling the lambda or the functor does not seem to be a problem for the compiler. The documentation of read_until describes match_condition as "The function object to be called to determine whether a match exists." I would expect lambda functions and functors to be accepted as a function object. Do I have an error in the declaration of lambda or completion_functor::operator()? Does anybody now, how to get this working? I tried boost_1_73_0 and boost_1_88_0 with g++ (Gentoo 14.3.1_p20250801 p4) 14.3.1 20250801 and clang version 20.1.8 Thanks in advance, Klebsch Mario Funktion | R&D Tel: +49 (0) 531 38 701 718 Raum: Braunschweig, E20 Diese E-Mail und die an sie angehängten Dateien sind ausschließlich für Personen oder Institutionen bestimmt, deren Namen oben aufgeführt sind. Sie können Informationen enthalten, die durch das Berufsgeheimnis geschützt sind und deren Weitergabe strengstens untersagt ist. Jede elektronische Nachricht kann geändert werden. ACTIA lehnt jede Verantwortung für diese Nachricht ab. Der Inhalt dieser Nachricht stellt keine Verpflichtung seitens unseres Unternehmens dar. Wenn Sie kein Empfänger sind, weisen wir Sie darauf hin, dass das Lesen, Vervielfältigen oder Verteilen strengstens untersagt ist. Wir bitten Sie daher, uns umgehend über diesen Brief zu informieren und diese Nachricht sowie eventuell beigefügte Unterlagen aus Ihrem Postfach zu löschen. Danke. This e-mail and the files attached to it are intended exclusively for persons or institutions whose names are listed above. They may contain information that is protected by professional secrecy and the disclosure of which is strictly prohibited. Any electronic message can be modified. ACTIA declines all responsibility for this message. The content of this message does not represent a commitment on the part of our company. If you are not a recipient, we would like to point out that reading, copying or distribution is strictly prohibited. We therefore ask you to inform us immediately about this letter and to delete this message and any accompanying documents from your mailbox. Thank you.

3 2

I have a segfault
by Anek Green 16 Oct '25

16 Oct '25

Basically, I'm writing a Boost.Beast webserver Stack trace follows: (gdb) f 0 #0 0x000000000041f6cain boost::asio::detail::op_queue_access::next<boost::asio::detail::scheduler_operation, boost::asio::detail::scheduler_o peration>(o1=@0x7f7fff7ad2a0: 0x2540be400, o2=0x75c5a8ed0bb0) at /usr/pkg/include/boost/asio/detail/op_queue.hpp:41 41 o1->next_ = o2; (gdb) bt #0 0x000000000041f6cain boost::asio::detail::op_queue_access::next<boost::asio::detail::scheduler_operation, boost::asio::detail::scheduler_o peration>(o1=@0x7f7fff7ad2a0: 0x2540be400, o2=0x75c5a8ed0bb0) at /usr/pkg/include/boost/asio/detail/op_queue.hpp:41 #1 0x000000000041d8bdin boost::asio::detail::op_queue<boost::asio::detail::scheduler_operation>::push(this=0x7f7fff7ad298, h=0x75c5a8ed0bb0) at /usr/pkg/include/boost/asio/detail/op_queue.hpp:110 #2 0x00000000004261c3in boost::asio::detail::scheduler::post_immediate_completion(this=0x7f7fff7ad1b8, op=0x75c5a8ed0bb0, is_continuation=false) at /usr/pkg/include/boost/asio/detail/impl/scheduler.ipp:363 #3 0x00000000004323d9in boost::asio::io_context::basic_executor_type<std::allocator<void>, 0ul>::execute<boost::asio::detail::executor_functi on>(this=0x7f7fff7ac5e0, f=...) at /usr/pkg/include/boost/asio/impl/io_context.hpp:215 #4 0x00000000004308eein boost::asio::execution::detail::any_executor_base::execute_ex<boost::asio::io_context::basic_executor_type<std::alloc ator<void>, 0ul> >(ex=..., f=...) at /usr/pkg/include/boost/asio/execution/any_executor.hpp:900 #5 0x0000000000433ecain boost::asio::execution::detail::any_executor_base::execute<boost::asio::detail::binder0<boost::asio::detail::spawned_ thread_resumer> >(this=0x7f7fff7ac5e0, f=...) at /usr/pkg/include/boost/asio/execution/any_executor.hpp:681 #6 0x0000000000432f99in boost::asio::detail::initiate_dispatch_with_executor<boost::asio::any_io_executor>::operator()<boost::asio::detail::s pawned_thread_resumer>(boost::asio::detail::spawned_thread_resumer&&, std::enable_if<boost::asio::execution::is_executor<std::conditional<true, boost::asio::any_io_executor, boost::asio::detail::spawned_thread_resumer>::type>::value, void>::type*, std::enable_if<!boost::asio::detail::i s_work_dispatcher_required<std::decay<boost::asio::detail::spawned_thread_resumer>::type, boost::asio::any_io_executor, void>::value, void>::ty pe*) const(this=0x7f7fff7ac5e0, handler=...) at /usr/pkg/include/boost/asio/detail/initiate_dispatch.hpp:106 #7 0x00000000004315a4in boost::asio::detail::completion_handler_async_result<boost::asio::detail::spawned_thread_resumer, void ()>::initiate< boost::asio::detail::initiate_dispatch_with_executor<boost::asio::any_io_executor>, boost::asio::detail::spawned_thread_resumer>(boost::asio::d etail::initiate_dispatch_with_executor<boost::asio::any_io_executor>&&, boost::asio::detail::spawned_thread_resumer&&)(initiation=..., token=...) at /usr/pkg/include/boost/asio/async_result.hpp:329 #8 0x000000000042fa2cin boost::asio::async_initiate<boost::asio::detail::spawned_thread_resumer, void (), boost::asio::detail::initiate_dispa tch_with_executor<boost::asio::any_io_executor>>(boost::asio::detail::initiate_dispatch_with_executor<boost::asio::any_io_executor>&&, boost::a sio::type_identity<boost::asio::detail::spawned_thread_resumer>::type&)(initiation=..., token=...) at /usr/pkg/include/boost/asio/async_result.hpp:629 #9 0x000000000042e5c6in boost::asio::dispatch<boost::asio::any_io_executor, boost::asio::detail::spawned_thread_resumer>(boost::asio::any_io_ executor const&, boost::asio::detail::spawned_thread_resumer&&, boost::asio::constraint<boost::asio::execution::is_executor<boost::asio::any_io _executor>::value||boost::asio::is_executor<boost::asio::any_io_executor>::value, int>::type)(ex=..., token=...) at /usr/pkg/include/boost/asio/dispatch.hpp:156 #10 0x000000000040b11ein boost::asio::detail::initiate_spawn<boost::asio::any_io_executor>::operator()<acceptor::spawn()::<lambda(std::__excep tion_ptr::exception_ptr)>, std::_Bind<void (acceptor::*(acceptor*, std::_Placeholder<1>))(boost::asio::basic_yield_context<boost::asio::any_io_ executor>)> >(struct {...} &&, std::_Bind<void (acceptor::*(acceptor*, std::_Placeholder<1>))(boost::asio::basic_yield_context<boost::asio::any _io_executor>)> &&) const(this=0x7f7fff7ac7c0, handler=..., f=...) at /usr/pkg/include/boost/asio/impl/spawn.hpp:917 #11 0x000000000040af52in boost::asio::detail::completion_handler_async_result<acceptor::spawn()::<lambda(std::__exception_ptr::exception_ptr)> , void(std::__exception_ptr::exception_ptr)>::initiate<boost::asio::detail::initiate_spawn<boost::asio::any_io_executor>, acceptor::spawn()::<l ambda(std::__exception_ptr::exception_ptr)>, std::_Bind<void (acceptor::*(acceptor*, std::_Placeholder<1>))(boost::asio::basic_yield_context<bo ost::asio::any_io_executor>)> >(boost::asio::detail::initiate_spawn<boost::asio::any_io_executor> &&, struct {...} &&)(initiation=..., token=...) at /usr/pkg/include/boost/asio/async_result.hpp:329 #12 0x000000000040aef0in boost::asio::async_initiate<acceptor::spawn()::<lambda(std::__exception_ptr::exception_ptr)>, void(std::__exception_p tr::exception_ptr), boost::asio::detail::initiate_spawn<boost::asio::any_io_executor>, std::_Bind<void (acceptor::*(acceptor*, std::_Placeholde r<1>))(boost::asio::basic_yield_context<boost::asio::any_io_executor>)> >(boost::asio::detail::initiate_spawn<boost::asio::any_io_executor> &&, --Type <RET> for more, q to quit, c to continue without paging-- boost::asio::type_identity_t &)(initiation=..., token=...) at /usr/pkg/include/boost/asio/async_result.hpp:629 #13 0x000000000040ae25in boost::asio::spawn<boost::asio::any_io_executor, std::_Bind<void (acceptor::*(acceptor*, std::_Placeholder<1>))(boost ::asio::basic_yield_context<boost::asio::any_io_executor>)>, acceptor::spawn()::<lambda(std::__exception_ptr::exception_ptr)> >(const boost::as io::any_io_executor &, std::_Bind<void (acceptor::*(acceptor*, std::_Placeholder<1>))(boost::asio::basic_yield_context<boost::asio::any_io_exec utor>)> &&, struct {...} &&, boost::asio::constraint_t)(ex=..., function=..., token=...) at /usr/pkg/include/boost/asio/impl/spawn.hpp:986 #14 0x000000000040a919in acceptor::spawn(this=0x7f7fff7ac8b0) at acceptor.c++:44 #15 0x00000000004098e2in run(ep=..., threads=4) at werewolf.c++:11 #16 0x0000000039373336in ??() #17 0x00007f7fff7ad2b8in ??() #18 0x00007f7fff7ad1f8in ??() #19 0x0000000000000007in ??() #20 0x00746c7561666564in ??() #21 0x0000000000000000in ??() In short, I've refactored stackful coroutine Beast example, and added a Redis database First issue I've encountered was DB calls freezing and cancelled, and after I moved redis::config initialization to db_conn::db_conn() (irrelevant change), the program started crashing at the very start. My OS is NetBSD Thanks for help, and have a good time! :) -- movepoind5y4ervjglu2wq2jztftbxfztv5r243k2gtcnxrmaxjw2yqd.onion Anek Green (Movepoint Solutions)

2 2

Question about boost.json and unescaped control characters
by Pavel Vazharov 16 Oct '25

16 Oct '25

Hi there, Is it possible to "make" the boost.json parser allow unescaped control characters in JSON string values? It seems to me that `allow_invalid_utf8` and `allow_invalid_utf16` parse_options doesn't help with this. I also looked at the source code of `parse_string` function and it seems to me that even if I provide a handler with `on_string` member function the parser will still throw an error because of the unescaped control characters before calling `on_string`. Maybe my only option is to escape such control characters before giving the JSON data to the boost json parser? Thanks, Pavel.

2 2

headerpad_max_install_names
by jmn＠rmnjmn.co.uk 16 Oct '25

16 Oct '25

How can I build boost 1_89_0 on MacOS with headerpad_max_install_names as a linkflags option. Without this present in the boost dylibs, I am unable to use install_name_tool -change to correctly define @rpath in my later project build. Error message I get is: "change rpath cannot be done because larger updated commands do not fit: relink with header pad or headerpad_max_install_names" Any advice would be appreciated in how to insert this option in project.jam Thanks....JMN

1 0

Crocc-compiling Boost from Linux for windows
by niXman 16 Sep '25

16 Sep '25

Hi, I'm trying to build Boost from Linux for Windows. I created user-config.jam file with the following content: using gcc : mingw : x86_64-w64-mingw32-g++ : <rc>x86_64-w64-mingw32-windres <as>x86_64-w64-mingw32-as ; I build using this command line: ./b2 --user-config=./user-config.jam --prefix=$HOME/boost-1.82.0 target-os=windows address-model=64 variant=release install but I get these messages when building boost.context: gcc.compile.asm bin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden/asm/ontop_x86_64_sysv_elf_gas.o ontop_x86_64_sysv_elf_gas.S: Assembler messages: ontop_x86_64_sysv_elf_gas.S:43: Warning: .type pseudo-op used outside of .def/.endef: ignored. ontop_x86_64_sysv_elf_gas.S:43: Error: junk at end of line, first unrecognized character is `o' libs/context/src/asm/ontop_x86_64_sysv_elf_gas.S:135: Warning: .size pseudo-op used outside of .def/.endef: ignored. libs/context/src/asm/ontop_x86_64_sysv_elf_gas.S:135: Error: junk at end of line, first unrecognized character is `o' libs/context/src/asm/ontop_x86_64_sysv_elf_gas.S:138: Error: junk at end of line, first unrecognized character is `-' "x86_64-w64-mingw32-g++" -x assembler-with-cpp -m64 -mthreads -O3 -finline-functions -Wno-inline -Wall -fvisibility=hidden -DBOOST_ALL_NO_LIB=1 -DBOOST_CONTEXT_SOURCE -DBOOST_DISABLE_ASSERTS -DNDEBUG -D_WIN32_WINNT=0x0601 -I"." -c -o "bin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden/asm/ontop_x86_64_sysv_elf_gas.o" "libs/context/src/asm/ontop_x86_64_sysv_elf_gas.S" ...failed gcc.compile.asm bin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden/asm/ontop_x86_64_sysv_elf_gas.o... gcc.compile.asm bin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden/asm/make_x86_64_sysv_elf_gas.o make_x86_64_sysv_elf_gas.S: Assembler messages: make_x86_64_sysv_elf_gas.S:44: Warning: .type pseudo-op used outside of .def/.endef: ignored. make_x86_64_sysv_elf_gas.S:44: Error: junk at end of line, first unrecognized character is `m' libs/context/src/asm/make_x86_64_sysv_elf_gas.S:144: Warning: .size pseudo-op used outside of .def/.endef: ignored. libs/context/src/asm/make_x86_64_sysv_elf_gas.S:144: Error: junk at end of line, first unrecognized character is `m' libs/context/src/asm/make_x86_64_sysv_elf_gas.S:147: Error: junk at end of line, first unrecognized character is `-' "x86_64-w64-mingw32-g++" -x assembler-with-cpp -m64 -mthreads -O3 -finline-functions -Wno-inline -Wall -fvisibility=hidden -DBOOST_ALL_NO_LIB=1 -DBOOST_CONTEXT_SOURCE -DBOOST_DISABLE_ASSERTS -DNDEBUG -D_WIN32_WINNT=0x0601 -I"." -c -o "bin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden/asm/make_x86_64_sysv_elf_gas.o" "libs/context/src/asm/make_x86_64_sysv_elf_gas.S" ...failed gcc.compile.asm bin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden/asm/make_x86_64_sysv_elf_gas.o... gcc.compile.asm bin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden/asm/jump_x86_64_sysv_elf_gas.o jump_x86_64_sysv_elf_gas.S: Assembler messages: jump_x86_64_sysv_elf_gas.S:44: Warning: .type pseudo-op used outside of .def/.endef: ignored. jump_x86_64_sysv_elf_gas.S:44: Error: junk at end of line, first unrecognized character is `j' libs/context/src/asm/jump_x86_64_sysv_elf_gas.S:139: Warning: .size pseudo-op used outside of .def/.endef: ignored. libs/context/src/asm/jump_x86_64_sysv_elf_gas.S:139: Error: junk at end of line, first unrecognized character is `j' libs/context/src/asm/jump_x86_64_sysv_elf_gas.S:142: Error: junk at end of line, first unrecognized character is `-' "x86_64-w64-mingw32-g++" -x assembler-with-cpp -m64 -mthreads -O3 -finline-functions -Wno-inline -Wall -fvisibility=hidden -DBOOST_ALL_NO_LIB=1 -DBOOST_CONTEXT_SOURCE -DBOOST_DISABLE_ASSERTS -DNDEBUG -D_WIN32_WINNT=0x0601 -I"." -c -o "bin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden/asm/jump_x86_64_sysv_elf_gas.o" "libs/context/src/asm/jump_x86_64_sysv_elf_gas.S" ...failed gcc.compile.asm bin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden/asm/jump_x86_64_sysv_elf_gas.o... ...skipped <pbin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden>libboost_context.a(clean) for lack of <pbin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden>asm/make_x86_64_sysv_elf_gas.o... ...skipped <pbin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden>libboost_context.a for lack of <pbin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden>asm/make_x86_64_sysv_elf_gas.o... ...skipped <p/home/andrew/boost-1.82.0/lib>libboost_context.a for lack of <pbin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden>libboost_context.a... ...skipped <pbin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden>libboost_context-variant-static.cmake for lack of <pbin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden>libboost_context.a... ...skipped <p/home/andrew/boost-1.82.0/lib/cmake/boost_context-1.82.0>libboost_context-variant-static.cmake for lack of <pbin.v2/libs/context/build/gcc-mingw/release/link-static/target-os-windows/threading-multi/visibility-hidden>libboost_context-variant-static.cmake... ...failed updating 3 targets... ...skipped 5 targets... any ideas how can I fix it? best!

2 2

[Regex] Undefined symbols when using Boost::regex_icu from CMake
by Lipódi László 11 Sep '25

11 Sep '25

Dear Boost::regex_icu users! I've ran into a problem while using the regex library of Boost with ICU compatibility mode. I am getting a lot of linker errors about ICU functions. This is all the linker errors I get: https://pastebin.com/eCj8Pi2m I am pretty sure that I'm getting this while using `boost::u32regex_token_iterator`. I'm using CMake to build my project and CPM (A wrapper around FetchContent). Here is my CMakeLists.txt: ``` cmake_minimum_required(VERSION 3.12) project(termeszetes_nyelvi) include(cmake/CPM.cmake) set(CMAKE_CXX_STANDARD 26) set(BOOST_REGEX_STANDALONE ON) set(ICU_ROOT "C:/Program Files/icu") CPMAddPackage("gh:boostorg/regex#boost-1.89.0") add_executable(termeszetes_nyelvi main.cpp regex_utils/regex_match_collector.hpp regex_utils/split_string_using_regex.hpp print_utils/format_map.hpp) target_link_libraries(termeszetes_nyelvi PRIVATE Boost::regex_icu)``` I have tried linking to all ICU components, but it did not resolve my errors. This is the function template that causes the error: https://gist.github.com/nevemlaci/3a1a14516626b263f11e887f9433cfd4 Please tell me if you need any more details. Thank you in advance, Laci

2 2

Radix Trie
by Pavel Vazharov 10 Sep '25

10 Sep '25

HI there, Is there a generic radix trie container in boost which can be used for longest prefix match? I mean, I couldn't find one in the boost containers libraries but maybe some library uses such a container internally and it's generic enough to be used with types other than strings? Thanks, Pavel.

4 6

Converting pointer-to-member to member index using Boost.PFR
by mail＠vittorioromeo.com 06 Sep '25

06 Sep '25

Consider the following struct: struct Particle { float scale; float opacity; float rotation; }; I want the following to compile: static_assert(indexOf<&Particle::scale>() == 0); static_assert(indexOf<&Particle::opacity>() == 1); static_assert(indexOf<&Particle::rotation>() == 2); I have managed to implement a working version using Boost.PFR: template <auto PM> consteval int indexOf() { using ClassType = typename PMTraits<decltype(PM)>::ClassType; constexpr ClassType obj{}; std::size_t result = -1; [&]<auto... Is>(std::index_sequence<Is...>) { (..., ( ( static_cast<const void*>(&(boost::pfr::get<Is>(obj))) == static_cast<const void*>(&(obj.*PM)) ) ? (result = Is) : 0 ) ); }(std::make_index_sequence<boost::pfr::tuple_size_v<ClassType>>{}); return result; } But I am displeased of the fact that I do need to create an object of type `ClassType` in order to make `obj.*PM` work. Is there a better way of doing this that (1) does not require the creation of an object at compile-time and/or (2) is more efficient to compile?

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