cannot compile standalone asio with exceptions turned off-CodePudding

I'm trying to build project which uses standalone asio as dependency. Problem is that with exceptions turned off (-fno-exceptions), I have to define throw_exception function (link to boost documentation), but no matter how I define that function, linker throws undefined reference. This is how I've tried to define throw_exception:

#define ASIO_NO_EXCEPTIONS
#include <asio/detail/throw_exception.hpp>

template <class E> 
void asio::detail::throw_exception(E const& e) {
// do something
}

I receive these linking errors:

/usr/bin/ld: libsioclient.a(sio_socket.cpp.o): in function `asio::detail::do_throw_error(std::error_code const&, char const*) [clone .isra.0]':
sio_socket.cpp:(.text 0x333): undefined reference to `void asio::detail::throw_exception<std::system_error>(std::system_error const&)'
/usr/bin/ld: _libsioclient.a(sio_socket.cpp.o): in function `void asio::execution::detail::any_executor_base::query_fn<void, asio::execution::prefer_only<asio::execution::detail::outstanding_work::tracked_t<0> > >(void*, void const*, void const*)':
sio_socket.cpp:(.text._ZN4asio9execution6detail17any_executor_base8query_fnIvNS0_11prefer_onlyINS1_16outstanding_work9tracked_tILi0EEEEEEEvPvPKvSB_[_ZN4asio9execution6detail17any_executor_base8query_fnIvNS0_11prefer_onlyINS1_16outstanding_work9tracked_tILi0EEEEEEEvPvPKvSB_] 0x28): undefined reference to `void asio::detail::throw_exception<asio::execution::bad_executor>(asio::execution::bad_executor const&)'
/usr/bin/ld: libsioclient.a(sio_socket.cpp.o): in function `void asio::execution::detail::any_executor_base::query_fn<void, asio::execution::prefer_only<asio::execution::detail::outstanding_work::untracked_t<0> > >(void*, void const*, void const*)':
sio_socket.cpp:(.text._ZN4asio9execution6detail17any_executor_base8query_fnIvNS0_11prefer_onlyINS1_16outstanding_work11untracked_tILi0EEEEEEEvPvPKvSB_[_ZN4asio9execution6detail17any_executor_base8query_fnIvNS0_11prefer_onlyINS1_16outstanding_work11untracked_tILi0EEEEEEEvPvPKvSB_] 0x28): undefined reference to `void asio::detail::throw_exception<asio::execution::bad_executor>(asio::execution::bad_executor const&)'
/usr/bin/ld: libsioclient.a(sio_socket.cpp.o): in function `void asio::execution::detail::any_executor_base::query_fn<void, asio::execution::prefer_only<asio::execution::detail::relationship::fork_t<0> > >(void*, void const*, void const*)':
sio_socket.cpp:(.text._ZN4asio9execution6detail17any_executor_base8query_fnIvNS0_11prefer_onlyINS1_12relationship6fork_tILi0EEEEEEEvPvPKvSB_[_ZN4asio9execution6detail17any_executor_base8query_fnIvNS0_11prefer_onlyINS1_12relationship6fork_tILi0EEEEEEEvPvPKvSB_] 0x28): undefined reference to `void asio::detail::throw_exception<asio::execution::bad_executor>(asio::execution::bad_executor const&)'
/usr/bin/ld: libsioclient.a(sio_socket.cpp.o): in function `void asio::execution::detail::any_executor_base::query_fn<void, asio::execution::prefer_only<asio::execution::detail::relationship::continuation_t<0> > >(void*, void const*, void const*)':
sio_socket.cpp:(.text._ZN4asio9execution6detail17any_executor_base8query_fnIvNS0_11prefer_onlyINS1_12relationship14continuation_tILi0EEEEEEEvPvPKvSB_[_ZN4asio9execution6detail17any_executor_base8query_fnIvNS0_11prefer_onlyINS1_12relationship14continuation_tILi0EEEEEEEvPvPKvSB_] 0x28): undefined reference to `void asio::detail::throw_exception<asio::execution::bad_executor>(asio::execution::bad_executor const&)'
/usr/bin/ld: libsioclient.a(sio_socket.cpp.o): in function `void asio::execution::detail::any_executor_base::query_fn<void, asio::execution::context_as_t<asio::execution_context&> >(void*, void const*, void const*)':
sio_socket.cpp:(.text._ZN4asio9execution6detail17any_executor_base8query_fnIvNS0_12context_as_tIRNS_17execution_contextEEEEEvPvPKvSA_[_ZN4asio9execution6detail17any_executor_base8query_fnIvNS0_12context_as_tIRNS_17execution_contextEEEEEvPvPKvSA_] 0x28): undefined reference to `void asio::detail::throw_exception<asio::execution::bad_executor>(asio::execution::bad_executor const&)'
/usr/bin/ld: libsioclient.a(sio_socket.cpp.o):sio_socket.cpp:(.text._ZN4asio9execution6detail17any_executor_base10require_fnINS0_12any_executorIJNS0_12context_as_tIRNS_17execution_contextEEENS1_8blocking7never_tILi0EEENS0_11prefer_onlyINS9_10possibly_tILi0EEEEENSC_INS1_16outstanding_work9tracked_tILi0EEEEENSC_INSG_11untracked_tILi0EEEEENSC_INS1_12relationship6fork_tILi0EEEEENSC_INSN_14continuation_tILi0EEEEEEEEvS8_EET_PKvSX_[_ZN4asio9execution6detail17any_executor_base10require_fnINS0_12any_executorIJNS0_12context_as_tIRNS_17execution_contextEEENS1_8blocking7never_tILi0EEENS0_11prefer_onlyINS9_10possibly_tILi0EEEEENSC_INS1_16outstanding_work9tracked_tILi0EEEEENSC_INSG_11untracked_tILi0EEEEENSC_INS1_12relationship6fork_tILi0EEEEENSC_INSN_14continuation_tILi0EEEEEEEEvS8_EET_PKvSX_] 0x2d): more undefined references to `void asio::detail::throw_exception<asio::execution::bad_executor>(asio::execution::bad_executor const&)' follow
/usr/bin/ld: libsioclient.a(sio_socket.cpp.o): in function `asio::detail::scheduler::scheduler(asio::execution_context&, int, bool, asio::detail::scheduler_task* (*)(asio::execution_context&)) [clone .part.0]':
sio_socket.cpp:(.text._ZN4asio6detail9schedulerC2ERNS_17execution_contextEibPFPNS0_14scheduler_taskES3_E.part.0[_ZN4asio6detail9schedulerC5ERNS_17execution_contextEibPFPNS0_14scheduler_taskES3_E] 0x228): undefined reference to `void asio::detail::throw_exception<std::system_error>(std::system_error const&)'
/usr/bin/ld: libsioclient.a(sio_socket.cpp.o): in function `asio::detail::epoll_reactor::notify_fork(asio::execution_context::fork_event)':
sio_socket.cpp:(.text._ZN4asio6detail13epoll_reactor11notify_forkENS_17execution_context10fork_eventE[_ZN4asio6detail13epoll_reactor11notify_forkENS_17execution_context10fork_eventE] 0x375): undefined reference to `void asio::detail::throw_exception<std::system_error>(std::system_error const&)'
/usr/bin/ld: libsioclient.a(sio_socket.cpp.o): in function `asio::detail::scheduler::scheduler(asio::execution_context&, int, bool, asio::detail::scheduler_task* (*)(asio::execution_context&))':
sio_socket.cpp:(.text._ZN4asio6detail9schedulerC2ERNS_17execution_contextEibPFPNS0_14scheduler_taskES3_E[_ZN4asio6detail9schedulerC5ERNS_17execution_contextEibPFPNS0_14scheduler_taskES3_E] 0x24a): undefined reference to `void asio::detail::throw_exception<std::system_error>(std::system_error const&)'
/usr/bin/ld: sio_socket.cpp:(.text._ZN4asio6detail9schedulerC2ERNS_17execution_contextEibPFPNS0_14scheduler_taskES3_E[_ZN4asio6detail9schedulerC5ERNS_17execution_contextEibPFPNS0_14scheduler_taskES3_E] 0x4f7): undefined reference to `void asio::detail::throw_exception<std::system_error>(std::system_error const&)'
/usr/bin/ld: libsioclient.a(sio_socket.cpp.o): in function `asio::execution_context::service* asio::detail::service_registry::create<asio::detail::epoll_reactor, asio::execution_context>(void*)':
sio_socket.cpp:(.text._ZN4asio6detail16service_registry6createINS0_13epoll_reactorENS_17execution_contextEEEPNS4_7serviceEPv[_ZN4asio6detail16service_registry6createINS0_13epoll_reactorENS_17execution_contextEEEPNS4_7serviceEPv] 0x5d6): undefined reference to `void asio::detail::throw_exception<std::system_error>(std::system_error const&)'
/usr/bin/ld: libsioclient.a(sio_client_impl.cpp.o): in function `std::_Function_handler<void (bool, std::shared_ptr<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const> const&), sio::client_impl::on_ping()::{lambda(bool, std::shared_ptr<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const>)#1}>::_M_invoke(std::_Any_data const&, bool&&, std::shared_ptr<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const> const&)':
sio_client_impl.cpp:(.text 0x3c40): undefined reference to `websocketpp::endpoint<websocketpp::connection<websocketpp::config::asio_client>, websocketpp::config::asio_client>::send(std::weak_ptr<void>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, websocketpp::frame::opcode::value)'
/usr/bin/ld: libsioclient.a(sio_client_impl.cpp.o): in function `sio::client_impl::connect_impl(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
sio_client_impl.cpp:(.text 0x988c): undefined reference to `websocketpp::connection<websocketpp::config::asio_client>::replace_header(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'

How to properly define throw_exception function or if I'm missing something, how can these errors be solved?

CodePudding user response：

You can try this, log() is the imaginary function you already use for logging ...

// somechere in a cpp file, preferably.

#include <boost/asio.hpp>

// ...

namespace boost::asio::detail {

template<>
void throw_exception(const asio::execution::bad_executor& e)
{
    // throw e;  // this is what the original function does
    LOG("asio::execution::bad_executor thrown\n");   // etc...
    exit(3);     // That's all you can do at this point.
}

template<>
void throw_exception(const std::system_error& e)
{
    LOG("std::system_error thrown\n");  // etc...
    exit(3);     // That's all you can do at this point.
}

}

You may need to declare more specializations as you go along.

CodePudding user response：

I find solution. Problem was that compiler threw implementation of throw_exception from code while compiling, and when linker tried to find that function, there simply was no throw_exception. I made it like this:

namespace asio::detail {

    template <typename Exception> void throw_exception(const Exception& e) {
        std::cerr << "Something went wrong..." << std::endl;
        std::terminate();
    }
}; // namespace asio::detail

If I call this function somewhere, I don't receive linking errors. Probably, I have to implement some kind of error handling instead of that and find a solution to make this function properly compiled and linked, but, at least, I've found a reason of that strange behaviour.