[boost] [ASIO] 1.70.0 async_read_until reports undefined symbol with MSVS 2010

Subject: [boost] [ASIO] 1.70.0 async_read_until reports undefined symbol with MSVS 2010
From: Kenneth Porter (shiva_at_[hidden])
Date: 2019-04-14 17:22:19

The following test code (inside #if 1) generates a LNK2019 (unresolved 
external symbol) with 1.70.0 but links successfully with 1.69.0. Inspecting 
read_until.hpp, I suspect the problem is with the enable_if expansion being 
too complex for the older compiler. (Hence the #if0 code which tests the 
individual conditions, but those seem to work fine.) The same code links 
with VS2019 and VS2015, and this linked under the previous Boost with 
VS2010.

int _tmain(int argc, _TCHAR* argv[])
{
   typedef boost::asio::streambuf buftype;
#if 0
   const bool v1 = boost::asio::is_dynamic_buffer_v1<typename 
boost::decay<buftype>::type>::value;
   const bool notv2 = !boost::asio::is_dynamic_buffer_v2<typename 
boost::decay<buftype>::type>::value;
#endif
#if 0
   void* cond = boost::enable_if<
                boost::asio::is_dynamic_buffer_v1<typename 
boost::decay<buftype>::type>::value
                && !boost::asio::is_dynamic_buffer_v2<typename 
boost::decay<buftype>::type>::value
                >::type* 0;
#endif
#if 1
   boost::asio::io_service ios;
   boost::asio::ip::tcp::socket socket(ios);
   boost::asio::streambuf buf;
   boost::asio::async_read_until(socket, buf, '\n', NULL);
#endif
   return 0;
}