Boost C++ Libraries: Ticket #13329: BOOST_ASIO_ENABLE

Boost C++ Libraries: Ticket #13329: BOOST_ASIO_ENABLE_CANCELIO must be globally defined https://svn.boost.org/trac10/ticket/13329 Today I spent several hours debugging a problem, that was caused by <code>#define BOOST_ASIO_ENABLE_CANCELIO</code> I added this #define only in those source files, where I had compiler warnings about cancel() failing on windows XP. This resulted in async_connect() failing. The problem was in boost::Casio::Detail::win_iocp_socket_service::async_accept(): <div class="wiki-code"><div class="code"><pre> start_accept_op(impl, peer.is_open(), p.p->new_socket(), impl.protocol_.family(), impl.protocol_.type(), impl.protocol_.protocol(), p.p->output_buffer(), p.p->address_length(), p.p); </pre></div></div> When I inspected the value if impl.protocol_.family_, the correct value was shown in the debugger. But when I stepped into impl.protocol_.family(), an incorrect value was shown. I found out, that in impl.protocol_.family(), the member family_ had a different address, then in the calling method async_accept(). This seems to be caused by the following code in boost::asio::detail::win_iocp_socket_service_base: <div class="wiki-code"><div class="code"><pre>#if defined(BOOST_ASIO_ENABLE_CANCELIO) // The ID of the thread from which it is safe to cancel asynchronous // operations. 0 means no asynchronous operations have been started yet. // ~0 means asynchronous operations have been started from more than one // thread, and cancellation is not supported for the socket. DWORD safe_cancellation_thread_id_; #endif // defined(BOOST_ASIO_ENABLE_CANCELIO) </pre></div></div> This makes the size of this class (and therefore the offsets of all member variables of derived classes depend on wether BOOST_ASIO_ENABLE_CANCELIO is defined or not. This only works, if BOOST_ASIO_ENABLE_CANCELIO is either defined or not in all sources, #include'ing boost/asio.hpp. If it is only #define'ed in those source files, where the compiler emits the warning about cancel() failing on windows XP, this problem may occur. I was not able to find any hint about this fact in the documentation of boost asio. I would just unconditionally declare the member variable safe_cancellation_thread_id_. I am no sure, whether this might trigger compiler warnings about an unused or uninitialized variable, but it should be possible to suppress these warnings. en-us Boost C++ Libraries /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/13329 Trac 1.4.3