/boost/lockfree/queue.hpp: error: static assertion failed: (boost::has_trivial_destructor<T>::value)

Question

I'm trying to substitute boost::lockfree::queue for std::queue in this file https://github.com/zaphoyd/websocketpp/blob/experimental/examples/broadcast_server/broadcast_server.cpp

I've added #include <boost/lockfree/queue.hpp>; changed line 130, std::queue<action> m_actions;, to boost::lockfree::queue<action> m_actions;; removed all lines having to do with locking; and changed line 103, m_actions.pop();, to m_actions.pop(a);.

I get these errors when I scons broadcast_server_lockfree in the project root after adding broadcast_server_lockfree = SConscript('#/broadcast_server_lockfree/SConscript',variant_dir = builddir + 'broadcast_server_lockfree',duplicate = 0) to the project root's SConstruct and using broadcast_server's SConstruct in the broadcast_server_lockfree directory:

root@server:~/websocketpp-experimental# scons broadcast_server_lockfree
scons: Reading SConscript files ...
C++11 build environment partially enabled
scons: done reading SConscript files.
scons: Building targets ...
scons: building associated VariantDir targets: build/release/broadcast_server_lockfree
g++ -o build/release/broadcast_server_lockfree/broadcast_server_lockfree.o -c -std=c++0x -Wall -Wcast-align -isystem /root/boost_1_53_0 -DNDEBUG -D_WEBSOCKETPP_CPP11_MEMORY_ -D_WEBSOCKETPP_CPP11_FUNCTIONAL_ -D_WEBSOCKETPP_CPP11_SYSTEM_ERROR_ -D_WEBSOCKETPP_CPP11_RANDOM_DEVICE_ -D_WEBSOCKETPP_NOEXCEPT_ -I. broadcast_server_lockfree/broadcast_server_lockfree.cpp
In file included from broadcast_server_lockfree/broadcast_server_lockfree.cpp:10:0:
/root/boost_1_53_0/boost/lockfree/queue.hpp: In instantiation of 'class boost::lockfree::queue<action>':
broadcast_server_lockfree/broadcast_server_lockfree.cpp:139:36:   required from here
/root/boost_1_53_0/boost/lockfree/queue.hpp:79:5: error: static assertion failed: (boost::has_trivial_destructor<T>::value)
/root/boost_1_53_0/boost/lockfree/queue.hpp:83:5: error: static assertion failed: (boost::has_trivial_assign<T>::value)
broadcast_server_lockfree/broadcast_server_lockfree.cpp: In member function 'void broadcast_server::process_messages()':
broadcast_server_lockfree/broadcast_server_lockfree.cpp:111:34: error: 'class boost::lockfree::queue<action>' has no member named 'front'
broadcast_server_lockfree/broadcast_server_lockfree.cpp:117:55: error: 'm_connection_lock' was not declared in this scope
broadcast_server_lockfree/broadcast_server_lockfree.cpp:120:55: error: 'm_connection_lock' was not declared in this scope
broadcast_server_lockfree/broadcast_server_lockfree.cpp:123:55: error: 'm_connection_lock' was not declared in this scope
In file included from broadcast_server_lockfree/broadcast_server_lockfree.cpp:10:0:
/root/boost_1_53_0/boost/lockfree/queue.hpp: In instantiation of 'boost::lockfree::queue<T, A0, A1, A2>::~queue() [with T = action; A0 = boost::parameter::void_; A1 = boost::parameter::void_; A2 = boost::parameter::void_]':
broadcast_server_lockfree/broadcast_server_lockfree.cpp:41:24:   required from here
/root/boost_1_53_0/boost/lockfree/queue.hpp:229:11: error: no matching function for call to 'action::action()'
/root/boost_1_53_0/boost/lockfree/queue.hpp:229:11: note: candidates are:
broadcast_server_lockfree/broadcast_server_lockfree.cpp:32:5: note: action::action(action_type, websocketpp::endpoint<websocketpp::connection<websocketpp::config::asio>, websocketpp::config::asio>::message_ptr)
broadcast_server_lockfree/broadcast_server_lockfree.cpp:32:5: note:   candidate expects 2 arguments, 0 provided
broadcast_server_lockfree/broadcast_server_lockfree.cpp:31:5: note: action::action(action_type, websocketpp::connection_hdl)
broadcast_server_lockfree/broadcast_server_lockfree.cpp:31:5: note:   candidate expects 2 arguments, 0 provided
broadcast_server_lockfree/broadcast_server_lockfree.cpp:30:8: note: action::action(const action&)
broadcast_server_lockfree/broadcast_server_lockfree.cpp:30:8: note:   candidate expects 1 argument, 0 provided
In file included from broadcast_server_lockfree/broadcast_server_lockfree.cpp:10:0:
/root/boost_1_53_0/boost/lockfree/queue.hpp: In instantiation of 'boost::lockfree::queue<T, A0, A1, A2>::node::node(boost::lockfree::queue<T, A0, A1, A2>::node::handle_type) [with T = action; A0 = boost::parameter::void_; A1 = boost::parameter::void_; A2 = boost::parameter::void_; boost::lockfree::queue<T, A0, A1, A2>::node::handle_type = boost::lockfree::queue<action>::node*]':
/root/boost_1_53_0/boost/lockfree/detail/freelist.hpp:82:13:   required from 'T* boost::lockfree::detail::freelist_stack<T, Alloc>::construct(const ArgumentType&) [with bool ThreadSafe = true; bool Bounded = false; ArgumentType = boost::lockfree::queue<action>::node*; T = boost::lockfree::queue<action>::node; Alloc = std::allocator<boost::lockfree::queue<action>::node>]'
/root/boost_1_53_0/boost/lockfree/queue.hpp:126:75:   required from 'void boost::lockfree::queue<T, A0, A1, A2>::initialize() [with T = action; A0 = boost::parameter::void_; A1 = boost::parameter::void_; A2 = boost::parameter::void_]'
/root/boost_1_53_0/boost/lockfree/queue.hpp:166:9:   required from 'boost::lockfree::queue<T, A0, A1, A2>::queue() [with T = action; A0 = boost::parameter::void_; A1 = boost::parameter::void_; A2 = boost::parameter::void_]'
broadcast_server_lockfree/broadcast_server_lockfree.cpp:41:24:   required from here
/root/boost_1_53_0/boost/lockfree/queue.hpp:109:52: error: no matching function for call to 'action::action()'
/root/boost_1_53_0/boost/lockfree/queue.hpp:109:52: note: candidates are:
broadcast_server_lockfree/broadcast_server_lockfree.cpp:32:5: note: action::action(action_type, websocketpp::endpoint<websocketpp::connection<websocketpp::config::asio>, websocketpp::config::asio>::message_ptr)
broadcast_server_lockfree/broadcast_server_lockfree.cpp:32:5: note:   candidate expects 2 arguments, 0 provided
broadcast_server_lockfree/broadcast_server_lockfree.cpp:31:5: note: action::action(action_type, websocketpp::connection_hdl)
broadcast_server_lockfree/broadcast_server_lockfree.cpp:31:5: note:   candidate expects 2 arguments, 0 provided
broadcast_server_lockfree/broadcast_server_lockfree.cpp:30:8: note: action::action(const action&)
broadcast_server_lockfree/broadcast_server_lockfree.cpp:30:8: note:   candidate expects 1 argument, 0 provided
scons: *** [build/release/broadcast_server_lockfree/broadcast_server_lockfree.o] Error 1
scons: building terminated because of errors.

I know next to nothing about c++, and searches on the error have yielded nothing (since I have no idea what I'm reading).

Here's the boost::lockfree::queue example if it helps. http://boost-sandbox.sourceforge.net/doc/html/lockfree/examples.html

Please show me how to correct this.

action

struct action {
    action(action_type t, connection_hdl h) : type(t), hdl(h) {}
    action(action_type t, server::message_ptr m) : type(t), msg(m) {}

    action_type type;
    websocketpp::connection_hdl hdl;
    server::message_ptr msg;
};

Answer 1

From the docs:

T must have a copy constructor, a trivial assignment operator, and a trivial destructor.

Thus your action class must look like the following:

class action
{
public:
    action(const action& rhs) { ... }
    //Implicitly defined destructor for itself and all member variables
    //Implicitly defined operator= for itself and all member variables

};

The static_asserts are complaining because your destructor and operator= are not implicitly defined by the compiler (or this is the case for at least one member variable of action).

Edit: I've had a quick look at the repo - I can't seem to find connection_hdl, and there is no message_ptr in template <typename endpoint> class server. Either way, one of websocketpp::connection_hdl hdl or server::message_ptr msg does not satisfy the above conditions. Just "dropping in" a lockfree queue instead of using a std::queue is likely a non-trivial task which will require a number of changes.

Answer 2

This question has been answer well by the above posting. Here I will provide more examples. The fruitful discussion gave a lots of guidance please read them. The real matter is the requirement for the template type of the queue. For practicality, let's look at some real use cases.

namespace lkf=boost::lockfree;
vector<lkf::spsc_queue<pair<Fastq*,int>, lkf::capacity<100>>> datastore;
//lkf::queue<pair<char*,char*>, lkf::capacity<100>> pile1, pile2;  //failed assert
lkf::queue<pair<char*,char*>*, lkf::capacity<100>> pile1, pile2;

The first line in the code passed the compiler (because it is spac_queue), but the second line pair failed the compiler (due to boost::ASSERT):

/usr/local/include/boost/lockfree/queue.hpp:99:5: error: static assertion failed: (boost::has_trivial_assign<T>::value)
     BOOST_STATIC_ASSERT((boost::has_trivial_assign<T>::value));

After converting pair to pointer type (line 3), the compiler is happy.

Could be boost assertion needs to be updated? Converting to pointer is one quick trick, may not be the best.

The boost lockfree::queue has three Requirements:

1. T must have a copy constructor
2. T must have a trivial assignment operator
3. T must have a trivial destructor

spsc_queue has two:

1. T must have a default constructor
2. T must be copyable

Answer 3

I got this error when I used std::string for the queue item type.

boost::lockfree::queue<string>(10000)

As many good people have pointed out in the answers here and here, string is not allowed to be used for boost::lockfree::queue.

It does compiled with char *

boost::lockfree::queue<char*>(10000)