Solution:
Mark it with LIBZMQ_UNUSED macro as per convention.

Problem: Since pull request #1730 was merged, protocol for REQ socket is
checked at the session level and this check does not take into account
the possibility of a request_id being part of the message. Thus the option
ZMQ_REQ_CORRELATE would no longer work.
This is now fixed: the possiblity of a 4 bytes integer being present
before the delimiter frame is taken into account (whether or not this
breaks the REQ/REP RFC is another issue).

Problem: when using ZMQ_REQ_RELAXED + ZMQ_REQ_CORRELATE and two 'send' are
executed in a row and no server is available at the time of the sends,
then the internal request_id used to identify messages gets corrupted and
the two messages end up with the same request_id. The correlation no
longer works in that case and you may end up with the wrong message.

Solution: make a copy of the request_id instance member before sending it
down the pipe.

Solution: Phase I - make precompiled.hpp be first file included in every source file

Otherwise, it's undefined behavior. ubsan catches alignment issues in
the libzmq test suite without this.

There's no value in this as the same pattern is repeated in several
places and it's fair to expect people to understand it.

Solution: revert to the old, one-liner style.

It's undefined behavior, and ubsan flags it.

Solution: update to 2016

When using ZMQ_REQ_RELAXED and a 'send' is executed after another 'send' the
previous code would terminate the 'reply_pipe' if any.
This is incorrect as terminating the reply pipe also terminates the send pipe
as they are the same (a pipe associated with a socket is bidirectional).
Doing a terminate on the pipe sets an internal flag called out_active to false
and the pipe can no longer send messages.
Removing the 'terminate' solves the problem. Removing this call is not an issue
as the incorrect ordering of messages that could be incurred is taken care of
by the ZMQ_REQ_CORRELATE option if needed.

Of course people still "can" distributed the sources under the
LGPLv3. However we provide COPYING.LESSER with additional grants.

Solution: specify these grants in the header of each source file.

Solution: update for 2015

Fixes #1320

* ZMQ_REQ_STRICT was negative option (default 1) which goes against
  the standard, where defaults are zero. I renamed this to
  ZMQ_REQ_RELAXED.

* ZMQ_REQ_REQUEST_IDS felt clumsy and describes the technical solution
  rather than the problem/requirement. I changed to ZMQ_REQ_CORRELATE
  which seems more explicit.

Added some missing (but existing in branch) files to libzmq11 project needed
to compile as static library by VS2012 (at least), and fixed some warnings.
One warning remains in raw_decoder.cpp, which I'm leaving for now because I'm
not sure how project owners would like to fix it.

It defaults to enabled. Switch it off to be able to send a new message
before the previous reply has been received.

* Fixes a terminate() call on a dangling pointer in the SEND_RESETS
  case.
* Fixes recv_reply_pipe() never receiving a message once the pipe it is
  waiting on is terminated.

This allows making a new request on a REQ socket by sending a new
message. Without the option set, calling send() after the first message
is done will continue to return an EFSM error.

It's useful for when a REQ is not getting a response. Previously that
meant creating a new socket or switching to DEALER.

* Documentation:
The default behavior of REQ sockets is to rely on the ordering of messages
to match requests and responses and that is usually sufficient. When this option
is set to 1, the REQ socket will prefix outgoing messages with an extra frame
containing a request id. That means the full message is (request id, 0,
user frames...). The REQ socket will discard all incoming messages that don't
begin with these two frames.

* Behavior change: When a REQ socket gets an invalid reply, it used to
  discard the message and return EAGAIN. REQ sockets still discard
  invalid messages, but keep looking at the next one automatically
  until a good one is found or there are no more messages.
* Add test_req_request_ids.

* Add lb_t::sendpipe() that returns the pipe that was used for sending,
  similar to fq_t::recvpipe().
* Add forwarder functions to dealer_t to access these two.
* Add logic to req_t to ignore replies on pipes that are not the one
  where the request was sent.
* Enable test in test_spec_req.

Copyrights had become ads for Sustrik's corporate sponsors, going against the original
agreement to share copyrights with the community (that agreement was: one line stating
iMatix copyright + one reference to AUTHORS file). The proliferation of corporate ads
is also unfair to the many individual authors. I've removed ALL corporate title from
the source files so the copyright statements can now be centralized in AUTHORS and
source files can be properly updated on an annual basis.

This patch introduces i_msg_sink and i_msg_source interfaces. This
allows us to make message encoder and decoder more general.

The patch extends the internal session's API with the reset method.
This method is used to reset a session's state so that it can
handle a new connection.

* Implemented new ctx API (_new, _destroy, _get, _set)
* Removed 'typesafe' macros from zmq.h
* Added support for MAX_SOCKETS (was tied into change for #337)
* Created new man pages

This allows us to actually report an error to the caller on resolve
failure, rather than asserting later on in the io thread.
Signed-off-by: Staffan Gimåker <staffan@spotify.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

However, the "durable socket" behaviour wasn't re-added.
Identities are used solely for routing in REQ/REP pattern.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

When zmq::req_t::xrecv detects that a response has no request ID
label, or the ID is the wrong size, it would return an EAGAIN, but
would not discard the remainder of the message.  This could allow the
remainder of the message to incorrectly "leak" into a future response,
if it is crafted to look like a reply with a valid response ID.
Discard all remaining message blocks, if the ID is invalid in any way.