October 2025 - Boost-users - lists.boost.org

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.

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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)

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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

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