* Address bind_handler ambiguous overload error when boost/bind/std_placeholders.hpp is included
Previously, the implementation of bind_handler made the assumption
that the trait boost::is_placeholder would be false for types
corresponding to values in the std::placeholders namespace.
However, boost/bind commit c85b31e3d200dda2a73cf0027a82c6d8e29066f8,
`Support use of standard placeholders with boost::bind`, added a new
header, boost/bind/std_placeholders.hpp, which adds specializations to
boost::is_placeholder for std::placeholders types.
When this header is included before a use of boost::bind_handler, it
results in compiler errors like the following, due to an internal
helper function having overloads for
enable_if<boost::is_placeholder...> and
enable_if<std::is_placeholder...>, which were previously assumed to be
mutually exclusive, but for which both conditions now are true:
../../../boost/beast/core/detail/bind_handler.hpp:126:18: error: call of overloaded 'extract(std::_Placeholder<1>, boost::beast::detail::tuple<int&&>)' is ambiguous
126 | h(extract(detail::get<S>(std::move(args)),
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
127 | std::forward<ValsTuple>(vals))...);
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This header is included in boost/bind/bind.hpp, and is transitively
included by headers in many boost libraries including:
algorithm
asio
atomic
graph
msm
multi_index
property_tree
ptr_container
python
signals2
test
thread
Making it possible that an include from one of these libraries will
randomly cause bind_handler to fail to compile.
This change addresses the issue by eliminating one of the ambiguous
overloads and ensuring that boost/bind/std_placeholders.hpp is
included in the bind_handler implementation file, so that the
enable_if<boost::is_placeholder...> overload can handle both
boost::placeholders and std::placeholders values. It also explicitly
adds a boost/bind/std_placeholders.hpp include to the bind_handler
unit test to prevent this issue from regressing.
* Address boost/bind/std_placeholders.hpp feature guards
boost/bind/std_placeholders.hpp has the following feature guards:
if !defined(BOOST_NO_CXX11_HDR_FUNCTIONAL) && !defined(BOOST_NO_CXX11_DECLTYPE) && !defined(BOOST_NO_CXX11_HDR_TYPE_TRAITS)
If this check fails, it will not detect std::placeholders values as
placeholders, making the previous solution fail.
This update restores the std::is_placeholder overload and adjusts the
SFINAE for the boost::is_placeholder overload so that it triggers only
if std::is_placeholder is false, making bind_handler work regardless
of whether std_placeholders.hpp's feature guard applies.
---------
Co-authored-by: Edward Nolan <enolan@maystreet.com>
buffers_generator uses default_completion.
websocket::stream has a rebinding constructor.
ssl_stream has a rebind_executor member.
basic_stream has rebinding constructor.
- websocket supports cancellation.
- Iterating test for ws cancellation.
- Only terminal cancellation is forwarded by default.
- basic_stream supports cancellation.
- supported cancellation is documented.
- http cancellation additions.
- Added cancellation_slot tests to http, utils and saved_handler.
- Added post to write.cpp, to avoid SIGSEV in test.
- Refresher describes cancellation in more detail.
Recent update zlib-1.2.11->1.2.12 included included a number of source
files in the Bjam/CMake changes that were previously excluded.
This leads to a bunch of C99 violation warnings (implicit function
declarations).
This commit excludes the culprits again, but leaves them actively
commented-out so the same mistake is less likely to happen by accident
in the future.
Mohammad Nejati
Klemens Morgenstern
Edward NolanandEdward Nolan
Christopher Kohlhoff
alandefreitas
Richard Hodges
sehe
JackyYin
Vinnie Falco
Glen Fernandes
Martijn Otto