Documentation: zmq_errno(3)

doc/Makefile.am

@@ -3,7 +3,7 @@ MAN3 = zmq_bind.3 zmq_close.3 zmq_connect.3 zmq_init.3 \
     zmq_msg_close.3 zmq_msg_copy.3 zmq_msg_data.3 zmq_msg_init.3 \
     zmq_msg_init_data.3 zmq_msg_init_size.3 zmq_msg_move.3 zmq_msg_size.3 \
     zmq_poll.3 zmq_recv.3 zmq_send.3 zmq_setsockopt.3 zmq_socket.3 \
-    zmq_strerror.3 zmq_term.3 zmq_version.3 zmq_getsockopt.3
+    zmq_strerror.3 zmq_term.3 zmq_version.3 zmq_getsockopt.3 zmq_errno.3
 MAN7 = zmq.7 zmq_tcp.7 zmq_pgm.7 zmq_epgm.7 zmq_inproc.7 zmq_ipc.7 \
     zmq_cpp.7
 MAN_DOC = $(MAN1) $(MAN3) $(MAN7)

doc/zmq.txt

@@ -164,9 +164,12 @@ shall return either a NULL value (if returning a pointer) or a negative value
 (if returning an integer), and the actual error code shall be stored in the
 'errno' variable.
 
-A _zmq_strerror()_ function is provided to translate 0MQ-specific error codes
-into error message strings. For further details refer to
-linkzmq:zmq_strerror[3].
+On non-POSIX systems some users may experience issues with retrieving the
+correct value of the 'errno' variable. The _zmq_errno()_ function is provided
+to assist in these cases; for details refer to linkzmq:zmq_errno[3].
+
+The _zmq_strerror()_ function is provided to translate 0MQ-specific error codes
+into error message strings; for details refer to linkzmq:zmq_strerror[3].
 
 
 MISCELLANEOUS

doc/zmq_errno.txt

+zmq_errno(3)
+============
+
+
+NAME
+----
+zmq_errno - retrieve value of errno for the calling thread
+
+
+SYNOPSIS
+--------
+*int zmq_errno (void);*
+
+
+DESCRIPTION
+-----------
+The _zmq_errno()_ function shall retrieve the value of the 'errno' variable for
+the calling thread.
+
+The _zmq_errno()_ function is provided to assist users on non-POSIX systems who
+are experiencing issues with retrieving the correct value of 'errno' directly.
+Specifically, users on Win32 systems whose application is using a different C
+runtime library from the C runtime library in use by 0MQ will need to use
+_zmq_errno()_ for correct operation.
+
+IMPORTANT: Users not experiencing issues with retrieving the correct value of
+'errno' should not use this function and should instead access the 'errno'
+variable directly.
+
+
+RETURN VALUE
+------------
+The _zmq_errno()_ function shall return the value of the 'errno' variable for
+the calling thread.
+
+
+ERRORS
+------
+No errors are defined.
+
+
+SEE ALSO
+--------
+linkzmq:zmq[7]
+
+
+AUTHORS
+-------
+The 0MQ documentation was written by Martin Sustrik <sustrik@250bpm.com> and
+Martin Lucina <mato@kotelna.sk>.