Problems with BOOST_TYPE_ERASURE_MEMBER

[jonesmz]

I'm currently using Boost 1.65 (It's what my operating system comes with).

I just pulled the newly merged code for #320 and am now seeing this error.

mqtt_cpp/include/mqtt/type_erased_socket.hpp:23: error: macro "BOOST_PP_SEQ_ELEM_III" requires 2 arguments, but only 1 given
BOOST_TYPE_ERASURE_MEMBER(has_async_read, async_read)
^~~~~~~~~~~~~~~~~~~

What version of boost do you consider the minimum required version?

[redboltz]

It seems that 1.67.0 or later is required.

But if you replace them, older boost version could be used.

// place them out of mqtt namespace (global namespace)
// BOOST_TYPE_ERASURE_MEMBER((name_space)(has_func_name), func_name, num_of_params)
BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_async_read), async_read, 3)
BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_async_write), async_write, 3)
BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_write), write, 2)
BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_post), post, 1)
BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_lowest_layer), lowest_layer, 0)
BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_close), close, 1)

I should update README.md.

[redboltz]

Could you replace and test the following file?

type_erased_socket.hpp

// Copyright Takatoshi Kondo 2019
//
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)

#if !defined(MQTT_TYPE_ERASED_SOCKET_HPP)
#define MQTT_TYPE_ERASED_SOCKET_HPP

#include <cstdlib>

#include <boost/config/workaround.hpp>
#include <boost/type_erasure/member.hpp>
#include <boost/system/error_code.hpp>
#include <boost/asio.hpp>

#include <mqtt/shared_any.hpp>

#if BOOST_VERSION >= 106700

namespace mqtt {

// New style boost type_erasure member fucntion concept definition
BOOST_TYPE_ERASURE_MEMBER(has_async_read, async_read)
BOOST_TYPE_ERASURE_MEMBER(has_async_write, async_write)
BOOST_TYPE_ERASURE_MEMBER(has_write, write)
BOOST_TYPE_ERASURE_MEMBER(has_post, post)
BOOST_TYPE_ERASURE_MEMBER(has_lowest_layer, lowest_layer)
BOOST_TYPE_ERASURE_MEMBER(has_close, close)

} // namespace mqtt

#else //  BOOST_VERSION >= 106700

// Old style boost type_erasure member fucntion concept definition
BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_async)_read, async_read, 3)
BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_async_write), async_write, 3)
BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_write), write, 2)
BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_post), post, 1)
BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_lowest_layer), lowest_layer, 0)
BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_close), close, 1)

#endif // BOOST_VERSION >= 106700

namespace mqtt {

namespace as = boost::asio;
using namespace boost::type_erasure;

/**
 * @brief type alias of the type erased socket
 * - mqtt::socket is a type erased socket.
 * - shared_ptr of any classes that have listed functions (or matching funtion template)
 *   can be used as the initializer of mqtt::socket.
 * - The class template endpoint uses mqtt::socket via listed interface.
 * - lowest_layer is provided for users to configure the socket (e.g. set delay, buffer size, etc)
 *
 */
using socket = shared_any<
    mpl::vector<
        destructible<>,
        has_async_read<void(as::mutable_buffer, std::function<void(boost::system::error_code const&, std::size_t)>)>,
        has_async_write<void(std::vector<as::const_buffer>, std::function<void(boost::system::error_code const&, std::size_t)>)>,
        has_write<std::size_t(std::vector<as::const_buffer>, boost::system::error_code&)>,
        has_post<void(std::function<void()>)>,
        has_lowest_layer<as::basic_socket<as::ip::tcp>&()>,
        has_close<void(boost::system::error_code&)>
    >
>;

} // namespace mqtt

#endif // MQTT_TYPE_ERASED_SOCKET_HPP

[jonesmz]

I tried to do the same earlier.

Unfortunately your test file given above results in this error, instead:

mqtt_cpp/include/mqtt/type_erased_socket.hpp:36: error: macro "BOOST_PP_SEQ_ELEM_III" requires 2 arguments, but only 1 given
 BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_async)_read, async_read, 3)
 ^~~~~~~~~~~~~~~~~~~

I am attempting to upgrade to boost 1.70, which will resolve the problem for me (I think?)

But you may still prefer to support boost < 1.67, and I am happy to help investigate that.

[redboltz]

Sorry

BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_async)_read, async_read, 3)

should be

BOOST_TYPE_ERASURE_MEMBER((mqtt)(has_async_read), async_read, 3)

Could you try again?

[jonesmz]

That appears to fix the first problem!!! Wonderful.

Now there's a new problem :-)

mqtt_cpp/include/mqtt/type_erased_socket.hpp:66: error: wrong number of template arguments (1, should be 2)
         has_lowest_layer<as::basic_socket<as::ip::tcp>&()>,
                                                      ^

[redboltz]

Could you replace

        has_lowest_layer<as::basic_socket<as::ip::tcp>&()>,

with

        has_lowest_layer<as::ip::tcp::socket::lowest_layer_type&()>,

?

[jonesmz]

That appears to have fixed it!

I still have plenty of other compiler errors in my code that i need to fix, but we appear to have fixed the boost 1.67 problem!

[redboltz]

Thank you for checking. I will send a PR to fix the problem you reported.

[redboltz]

Fixed by #347.

[ropieur]

I got the master branch and I encounter the same issue with boost 1.70.0
The error disappears, when forcing for version < 1.67 as follows at mqtt/type_erased_socket.hpp:20
#if 0 // BOOST_VERSION >= 106700

[redboltz]

@ropieur , the compile error isn't reproduced on my environment.
I tested on 1.70.0 and 1.71.0.
I cleaned build directory each time (using rm -rf * , not make clean).
Could you try this?

[ropieur]

@redboltz,
I cleaned up all my environment and build from scratch, but the issue still persists.
FYI, I am using g++ 7.4.0 under ubuntu 18.04.
Also, I added the following lines to verify the boost version

#include <boost/preprocessor/stringize.hpp>
#pragma message "boost version is " BOOST_PP_STRINGIZE(BOOST_VERSION)

Output

...mqtt_cpp/obj/include/mqtt/type_erased_socket.hpp:21:69: note: #pragma message: boost version is 107000

[redboltz]

@ropieur , the error message you got is the same as follows ?

mqtt_cpp/include/mqtt/type_erased_socket.hpp:23: error: macro "BOOST_PP_SEQ_ELEM_III" requires 2 arguments, but only 1 given
BOOST_TYPE_ERASURE_MEMBER(has_async_read, async_read)
^~~~~~~~~~~~~~~~~~~

[ropieur]

@redboltz,
I got the following error:

mqtt_cpp/obj/include/mqtt/type_erased_socket.hpp:25:1: error: ISO C++11 requires at least one argument for the "..." in a variadic macro
 BOOST_TYPE_ERASURE_MEMBER(has_async_read, async_read)
 ^~~~~~~~~~~~~~

[redboltz]

@ropieur , it is different error from the error first reported.

I reproduced the error, see
https://wandbox.org/permlink/goH0ctebZGtsBfCk

It is caused by pedantic flags. So Boost.TypeErasure new macro seems to use out of standard expansion. I guess you set the flag.

Could you try compile without pedantic flag?
I just want to know what is the reason of the error.

I know setting pedantic flag is reasonable.
After your checked, I will remove new version macros.

[ropieur]

@redboltz,
I confirm that we use pedantic flag. I temporarily disabled it locally in my build environment and the compilation succeeded. But I can't definitely not workaround it for code production due to internal policies.

[redboltz]

@ropieur , thank you for confirming.

Of course, I don't enforce removing pedantic flag. I will send the PR to fix the issue. Please wait a moment.