I'm trying to use Boost.Asio's async_read_until()
free function, but I'm having trouble specifying a member function as the callback using std::bind()
. I have no trouble using this idiom for other Boost.Asio functions, so I'm confused as to why it's not working for async_read_until()
.
Here's my example:
#include <functional>
#include <boost/asio.hpp>
#include <boost/bind.hpp>
class Test
{
public:
boost::asio::streambuf buf;
boost::asio::ip::tcp::socket sock;
Test(boost::asio::io_service& io) :
sock(io)
{
}
void readComplete(const boost::system::error_code& error,
std::size_t bytesTransferred)
{
}
void invoke()
{
boost::asio::async_read_until(sock,
buf,
'\n',
std::bind(&Test::readComplete,
this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
}
};
int main(int argc, char** argv)
{
boost::asio::io_service io;
Test t(io);
t.invoke();
return 0;
}
In this case, the compilation fails with the following error (along with other template-compiler-error-barf):
In file included from /home/me/eclipse-workspace/practice/main.cpp:4:
In file included from /usr/include/boost/asio.hpp:91:
In file included from /usr/include/boost/asio/read_until.hpp:921:
/usr/include/boost/asio/impl/read_until.hpp:707:3: error: static_assert failed "ReadHandler type requirements not met"
BOOST_ASIO_READ_HANDLER_CHECK(ReadHandler, handler) type_check;
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/boost/asio/detail/handler_type_requirements.hpp:153:3: note: expanded from macro 'BOOST_ASIO_READ_HANDLER_CHECK'
BOOST_ASIO_HANDLER_TYPE_REQUIREMENTS_ASSERT( \
^
/usr/include/boost/asio/detail/handler_type_requirements.hpp:105:6: note: expanded from macro 'BOOST_ASIO_HANDLER_TYPE_REQUIREMENTS_ASSERT'
static_assert(expr, msg);
^ ~~~~
/home/me/eclipse-workspace/practice/main.cpp:24:22: note: in instantiation of function template specialization 'boost::asio::async_read_until<boost::asio::basic_stream_socket<boost::asio::ip::tcp,
boost::asio::stream_socket_service<boost::asio::ip::tcp> >, std::allocator<char>, std::_Bind<std::_Mem_fn<void (Test::*)(const boost::system::error_code &, unsigned long)>
(Test *, boost::arg<1> (*)(), boost::arg<2> (*)())> >' requested here
boost::asio::async_read_until(sock,
^
So it's telling me that my function signature is wrong, which it doesn't appear to be.
I don't understand why it's not working, and what I more so don't understand is that if I just swap out std::bind()
for boost::bind()
, it builds and works completely fine. Could someone please help me understand this?
FYI I'm using Boost 1.58.0 (from the Ubuntu 16.04 Universe repos) and clang++ 3.8 with C++11.
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