Updated the parameter of set_accept_handler() from endpoint_t to std:…

[redboltz]

…:shared_ptr<endpoint_t>.

For set_*_handler(), capture std::weak_ptr<endpoint_t> at
test_broker and examples.

I think that weak_ptr is redundant. Reference is good enough because
shared_ptr lifetime is kept by start_session(life_keeper).

However, wp.lock() is easy to detect if the lifetime is over unexpectedly.

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[jonesmz]

Are you certain that

close_proc(connections, subs, wp.lock());

is sufficient? wp.lock() may return nullptr

[redboltz]

Yes I'm certain that wp.lock() never return nullptr at close handler.

I inserted the following BOOST_ASSERT:

BOOST_ASSERT(wp.lock());
close_proc(connections, subs, wp.lock());

then no assertion failure occurred.

Let me explain why I'm certain about that.

First, the lifetime of the session (shared_ptr) is copy captured by start_session(). It is mandatory convention.

            ep.start_session(std::make_tuple(std::move(spep), std::move(g)));

wp.lock() is called from the close handler.

close_proc(connections, subs, wp.lock());

is called from h_close_().

h_close_() is called from handle_close().
https://github.com/redboltz/mqtt_cpp/blob/accept_cb_shared_ptr/include/mqtt/endpoint.hpp#L7644-L7646

handle_close() is called from handle_close_or_error()
https://github.com/redboltz/mqtt_cpp/blob/accept_cb_shared_ptr/include/mqtt/endpoint.hpp#L7598-L7634
at the line
https://github.com/redboltz/mqtt_cpp/blob/accept_cb_shared_ptr/include/mqtt/endpoint.hpp#L7626.

handle_close_or_error() is called from the lambda expression at handle_remaining_length() and check_error_and_transferred_length().

At handle_remaining_length() lambda expression, session_life_keeper is held by its capture list. So the lifetime of the session is enable.
https://github.com/redboltz/mqtt_cpp/blob/accept_cb_shared_ptr/include/mqtt/endpoint.hpp#L8055

check_error_and_transferred_length() is called from various places and session_life_keeper is enable at all places similar to handle_remaining_length().

So wp->lock() never return nullptr.