[ViewVC] Diff of: cvs/libev/ev.3

Comparing libev/ev.3 (file contents):
Revision 1.85 by root, Tue Jan 11 13:45:28 2011 UTC vs.
Revision 1.99 by root, Mon Jun 10 00:14:23 2013 UTC

-.\" Automatically generated by Pod::Man 2.22 (Pod::Simple 3.07)
+.\" Automatically generated by Pod::Man 2.25 (Pod::Simple 3.20)
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 .IX Title "LIBEV 3"
-.TH LIBEV 3 "2011-01-11" "libev-4.03" "libev - high performance full featured event loop"
+.TH LIBEV 3 "2013-06-07" "libev-4.15" "libev - high performance full featured event loop"
 .\" For nroff, turn off justification.  Always turn off hyphenation; it makes
 .\" way too many mistakes in technical documents.
 .if n .ad l
 .nh
 .SH "NAME"
 \&     ev_timer_start (loop, &timeout_watcher);
 \&
 \&     // now wait for events to arrive
 \&     ev_run (loop, 0);
 \&
-\&     // unloop was called, so exit
+\&     // break was called, so exit
 \&     return 0;
 \&   }
 .Ve
 .SH "ABOUT THIS DOCUMENT"
 .IX Header "ABOUT THIS DOCUMENT"
 loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and
 \&\f(CW\*(C`ev_check\*(C'\fR watchers) as well as file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even
 limited support for fork events (\f(CW\*(C`ev_fork\*(C'\fR).
 .PP
 It also is quite fast (see this
-<benchmark> comparing it to libevent
+benchmark <http://libev.schmorp.de/bench.html> comparing it to libevent
 for example).
 .SS "\s-1CONVENTIONS\s0"
 .IX Subsection "CONVENTIONS"
 Libev is very configurable. In this manual the default (and most common)
 configuration will be described, which supports multiple event loops. For
 .IP "ev_tstamp ev_time ()" 4
 .IX Item "ev_tstamp ev_time ()"
 Returns the current time as libev would use it. Please note that the
 \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp
 you actually want to know. Also interesting is the combination of
-\&\f(CW\*(C`ev_update_now\*(C'\fR and \f(CW\*(C`ev_now\*(C'\fR.
+\&\f(CW\*(C`ev_now_update\*(C'\fR and \f(CW\*(C`ev_now\*(C'\fR.
 .IP "ev_sleep (ev_tstamp interval)" 4
 .IX Item "ev_sleep (ev_tstamp interval)"
-Sleep for the given interval: The current thread will be blocked until
+Sleep for the given interval: The current thread will be blocked
-either it is interrupted or the given time interval has passed. Basically
+until either it is interrupted or the given time interval has
+passed (approximately \- it might return a bit earlier even if not
+interrupted). Returns immediately if \f(CW\*(C`interval <= 0\*(C'\fR.
+.Sp
-this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR.
+Basically this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR.
+.Sp
+The range of the \f(CW\*(C`interval\*(C'\fR is limited \- libev only guarantees to work
+with sleep times of up to one day (\f(CW\*(C`interval <= 86400\*(C'\fR).
 .IP "int ev_version_major ()" 4
 .IX Item "int ev_version_major ()"
 .PD 0
 .IP "int ev_version_minor ()" 4
 .IX Item "int ev_version_minor ()"
 current system. To find which embeddable backends might be supported on
 the current system, you would need to look at \f(CW\*(C`ev_embeddable_backends ()
 & ev_supported_backends ()\*(C'\fR, likewise for recommended ones.
 .Sp
 See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
-.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
+.IP "ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())" 4
-.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
+.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())"
 Sets the allocation function to use (the prototype is similar \- the
 semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is
 used to allocate and free memory (no surprises here). If it returns zero
 when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort
 or take some potentially destructive action.
 \&   }
 \&
 \&   ...
 \&   ev_set_allocator (persistent_realloc);
 .Ve
-.IP "ev_set_syserr_cb (void (*cb)(const char *msg))" 4
+.IP "ev_set_syserr_cb (void (*cb)(const char *msg) throw ())" 4
-.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg))"
+.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg) throw ())"
 Set the callback function to call on a retryable system call error (such
 as failed select, poll, epoll_wait). The message is a printable string
 indicating the system call or subsystem causing the problem. If this
 callback is set, then libev will expect it to remedy the situation, no
 matter what, when it returns. That is, libev will generally retry the
 .IX Item "EVFLAG_NOENV"
 If this flag bit is or'ed into the flag value (or the program runs setuid
 or setgid) then libev will \fInot\fR look at the environment variable
 \&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
 override the flags completely if it is found in the environment. This is
-useful to try out specific backends to test their performance, or to work
+useful to try out specific backends to test their performance, to work
-around bugs.
+around bugs, or to make libev threadsafe (accessing environment variables
+cannot be done in a threadsafe way, but usually it works if no other
+thread modifies them).
 .ie n .IP """EVFLAG_FORKCHECK""" 4
 .el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
 .IX Item "EVFLAG_FORKCHECK"
 Instead of calling \f(CW\*(C`ev_loop_fork\*(C'\fR manually after a fork, you can also
 make libev check for a fork in each iteration by enabling this flag.
 example) that can't properly initialise their signal masks.
 .ie n .IP """EVFLAG_NOSIGMASK""" 4
 .el .IP "\f(CWEVFLAG_NOSIGMASK\fR" 4
 .IX Item "EVFLAG_NOSIGMASK"
 When this flag is specified, then libev will avoid to modify the signal
-mask. Specifically, this means you ahve to make sure signals are unblocked
+mask. Specifically, this means you have to make sure signals are unblocked
 when you want to receive them.
 .Sp
 This behaviour is useful when you want to do your own signal handling, or
 want to handle signals only in specific threads and want to avoid libev
 unblocking the signals.
+.Sp
+It's also required by \s-1POSIX\s0 in a threaded program, as libev calls
+\&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified.
 .Sp
 This flag's behaviour will become the default in future versions of libev.
 .ie n .IP """EVBACKEND_SELECT""  (value 1, portable select backend)" 4
 .el .IP "\f(CWEVBACKEND_SELECT\fR  (value 1, portable select backend)" 4
 .IX Item "EVBACKEND_SELECT  (value 1, portable select backend)"
 .el .IP "\f(CWEVBACKEND_EPOLL\fR   (value 4, Linux)" 4
 .IX Item "EVBACKEND_EPOLL   (value 4, Linux)"
 Use the linux-specific \fIepoll\fR\|(7) interface (for both pre\- and post\-2.6.9
 kernels).
 .Sp
-For few fds, this backend is a bit little slower than poll and select,
+For few fds, this backend is a bit little slower than poll and select, but
-but it scales phenomenally better. While poll and select usually scale
+it scales phenomenally better. While poll and select usually scale like
-like O(total_fds) where n is the total number of fds (or the highest fd),
+O(total_fds) where total_fds is the total number of fds (or the highest
-epoll scales either O(1) or O(active_fds).
+fd), epoll scales either O(1) or O(active_fds).
 .Sp
 The epoll mechanism deserves honorable mention as the most misdesigned
 of the more advanced event mechanisms: mere annoyances include silently
 dropping file descriptors, requiring a system call per change per file
 descriptor (and unnecessary guessing of parameters), problems with dup,
 0.1ms) and so on. The biggest issue is fork races, however \- if a program
 forks then \fIboth\fR parent and child process have to recreate the epoll
 set, which can take considerable time (one syscall per file descriptor)
 and is of course hard to detect.
 .Sp
-Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work, but
+Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work,
-of course \fIdoesn't\fR, and epoll just loves to report events for totally
+but of course \fIdoesn't\fR, and epoll just loves to report events for
-\&\fIdifferent\fR file descriptors (even already closed ones, so one cannot
+totally \fIdifferent\fR file descriptors (even already closed ones, so
-even remove them from the set) than registered in the set (especially
+one cannot even remove them from the set) than registered in the set
-on \s-1SMP\s0 systems). Libev tries to counter these spurious notifications by
+(especially on \s-1SMP\s0 systems). Libev tries to counter these spurious
-employing an additional generation counter and comparing that against the
+notifications by employing an additional generation counter and comparing
-events to filter out spurious ones, recreating the set when required. Last
+that against the events to filter out spurious ones, recreating the set
+when required. Epoll also erroneously rounds down timeouts, but gives you
+no way to know when and by how much, so sometimes you have to busy-wait
+because epoll returns immediately despite a nonzero timeout. And last
 not least, it also refuses to work with some file descriptors which work
 perfectly fine with \f(CW\*(C`select\*(C'\fR (files, many character devices...).
 .Sp
-Epoll is truly the train wreck analog among event poll mechanisms,
+Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
-a frankenpoll, cobbled together in a hurry, no thought to design or
+cobbled together in a hurry, no thought to design or interaction with
-interaction with others.
+others. Oh, the pain, will it ever stop...
 .Sp
 While stopping, setting and starting an I/O watcher in the same iteration
 will result in some caching, there is still a system call per such
 incident (because the same \fIfile descriptor\fR could point to a different
 \&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed
 .Sp
 It scales in the same way as the epoll backend, but the interface to the
 kernel is more efficient (which says nothing about its actual speed, of
 course). While stopping, setting and starting an I/O watcher does never
 cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to
-two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (but
+two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (you
-sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
+might have to leak fd's on fork, but it's more sane than epoll) and it
-cases
+drops fds silently in similarly hard-to-detect cases.
 .Sp
 This backend usually performs well under most conditions.
 .Sp
 While nominally embeddable in other event loops, this doesn't work
 everywhere, so you might need to test for this. And since it is broken
 among the OS-specific backends (I vastly prefer correctness over speed
 hacks).
 .Sp
 On the negative side, the interface is \fIbizarre\fR \- so bizarre that
 even sun itself gets it wrong in their code examples: The event polling
-function sometimes returning events to the caller even though an error
+function sometimes returns events to the caller even though an error
 occurred, but with no indication whether it has done so or not (yes, it's
-even documented that way) \- deadly for edge-triggered interfaces where
+even documented that way) \- deadly for edge-triggered interfaces where you
-you absolutely have to know whether an event occurred or not because you
+absolutely have to know whether an event occurred or not because you have
-have to re-arm the watcher.
+to re-arm the watcher.
 .Sp
 Fortunately libev seems to be able to work around these idiocies.
 .Sp
 This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
 \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
 given loop other than \f(CW\*(C`ev_resume\*(C'\fR, and you \fBmust not\fR call \f(CW\*(C`ev_resume\*(C'\fR
 without a previous call to \f(CW\*(C`ev_suspend\*(C'\fR.
 .Sp
 Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the
 event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR).
-.IP "ev_run (loop, int flags)" 4
+.IP "bool ev_run (loop, int flags)" 4
-.IX Item "ev_run (loop, int flags)"
+.IX Item "bool ev_run (loop, int flags)"
 Finally, this is it, the event handler. This function usually is called
 after you have initialised all your watchers and you want to start
 handling events. It will ask the operating system for any new events, call
-the watcher callbacks, an then repeat the whole process indefinitely: This
+the watcher callbacks, and then repeat the whole process indefinitely: This
 is why event loops are called \fIloops\fR.
 .Sp
 If the flags argument is specified as \f(CW0\fR, it will keep handling events
 until either no event watchers are active anymore or \f(CW\*(C`ev_break\*(C'\fR was
 called.
+.Sp
+The return value is false if there are no more active watchers (which
+usually means \*(L"all jobs done\*(R" or \*(L"deadlock\*(R"), and true in all other cases
+(which usually means " you should call \f(CW\*(C`ev_run\*(C'\fR again").
 .Sp
 Please note that an explicit \f(CW\*(C`ev_break\*(C'\fR is usually better than
 relying on all watchers to be stopped when deciding when a program has
 finished (especially in interactive programs), but having a program
 that automatically loops as long as it has to and no longer by virtue
 of relying on its watchers stopping correctly, that is truly a thing of
 beauty.
 .Sp
-This function is also \fImostly\fR exception-safe \- you can break out of
+This function is \fImostly\fR exception-safe \- you can break out of a
-a \f(CW\*(C`ev_run\*(C'\fR call by calling \f(CW\*(C`longjmp\*(C'\fR in a callback, throwing a \*(C+
+\&\f(CW\*(C`ev_run\*(C'\fR call by calling \f(CW\*(C`longjmp\*(C'\fR in a callback, throwing a \*(C+
 exception and so on. This does not decrement the \f(CW\*(C`ev_depth\*(C'\fR value, nor
 will it clear any outstanding \f(CW\*(C`EVBREAK_ONE\*(C'\fR breaks.
 .Sp
 A flags value of \f(CW\*(C`EVRUN_NOWAIT\*(C'\fR will look for new events, will handle
 those events and any already outstanding ones, but will not wait and
 This is useful if you are waiting for some external event in conjunction
 with something not expressible using other libev watchers (i.e. "roll your
 own \f(CW\*(C`ev_run\*(C'\fR"). However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
 usually a better approach for this kind of thing.
 .Sp
-Here are the gory details of what \f(CW\*(C`ev_run\*(C'\fR does:
+Here are the gory details of what \f(CW\*(C`ev_run\*(C'\fR does (this is for your
+understanding, not a guarantee that things will work exactly like this in
+future versions):
 .Sp
 .Vb 10
 \&   \- Increment loop depth.
 \&   \- Reset the ev_break status.
 \&   \- Before the first iteration, call any pending watchers.
 .Sp
 .Vb 4
 \&   ... queue jobs here, make sure they register event watchers as long
 \&   ... as they still have work to do (even an idle watcher will do..)
 \&   ev_run (my_loop, 0);
-\&   ... jobs done or somebody called unloop. yeah!
+\&   ... jobs done or somebody called break. yeah!
 .Ve
 .IP "ev_break (loop, how)" 4
 .IX Item "ev_break (loop, how)"
 Can be used to make a call to \f(CW\*(C`ev_run\*(C'\fR return early (but only after it
 has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
 overhead for the actual polling but can deliver many events at once.
 .Sp
 By setting a higher \fIio collect interval\fR you allow libev to spend more
 time collecting I/O events, so you can handle more events per iteration,
 at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and
-\&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null value will
+\&\f(CW\*(C`ev_timer\*(C'\fR) will not be affected. Setting this to a non-null value will
 introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. The
 sleep time ensures that libev will not poll for I/O events more often then
-once per this interval, on average.
+once per this interval, on average (as long as the host time resolution is
+good enough).
 .Sp
 Likewise, by setting a higher \fItimeout collect interval\fR you allow libev
 to spend more time collecting timeouts, at the expense of increased
 latency/jitter/inexactness (the watcher callback will be called
 later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null
 this callback instead. This is useful, for example, when you want to
 invoke the actual watchers inside another context (another thread etc.).
 .Sp
 If you want to reset the callback, use \f(CW\*(C`ev_invoke_pending\*(C'\fR as new
 callback.
-.IP "ev_set_loop_release_cb (loop, void (*release)(\s-1EV_P\s0), void (*acquire)(\s-1EV_P\s0))" 4
+.IP "ev_set_loop_release_cb (loop, void (*release)(\s-1EV_P\s0) throw (), void (*acquire)(\s-1EV_P\s0) throw ())" 4
-.IX Item "ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))"
+.IX Item "ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())"
 Sometimes you want to share the same loop between multiple threads. This
 can be done relatively simply by putting mutex_lock/unlock calls around
 each call to a libev function.
 .Sp
 However, \f(CW\*(C`ev_run\*(C'\fR can run an indefinite time, so it is not feasible
 to wait for it to return. One way around this is to wake up the event
-loop via \f(CW\*(C`ev_break\*(C'\fR and \f(CW\*(C`av_async_send\*(C'\fR, another way is to set these
+loop via \f(CW\*(C`ev_break\*(C'\fR and \f(CW\*(C`ev_async_send\*(C'\fR, another way is to set these
 \&\fIrelease\fR and \fIacquire\fR callbacks on the loop.
 .Sp
 When set, then \f(CW\*(C`release\*(C'\fR will be called just before the thread is
 suspended waiting for new events, and \f(CW\*(C`acquire\*(C'\fR is called just
 afterwards.
 .PD 0
 .ie n .IP """EV_CHECK""" 4
 .el .IP "\f(CWEV_CHECK\fR" 4
 .IX Item "EV_CHECK"
 .PD
-All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_run\*(C'\fR starts
+All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_run\*(C'\fR starts to
-to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after
+gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are queued (not invoked)
-\&\f(CW\*(C`ev_run\*(C'\fR has gathered them, but before it invokes any callbacks for any
+just after \f(CW\*(C`ev_run\*(C'\fR has gathered them, but before it queues any callbacks
+for any received events. That means \f(CW\*(C`ev_prepare\*(C'\fR watchers are the last
+watchers invoked before the event loop sleeps or polls for new events, and
+\&\f(CW\*(C`ev_check\*(C'\fR watchers will be invoked before any other watchers of the same
+or lower priority within an event loop iteration.
+.Sp
-received events. Callbacks of both watcher types can start and stop as
+Callbacks of both watcher types can start and stop as many watchers as
-many watchers as they want, and all of them will be taken into account
+they want, and all of them will be taken into account (for example, a
-(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
+\&\f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep \f(CW\*(C`ev_run\*(C'\fR from
-\&\f(CW\*(C`ev_run\*(C'\fR from blocking).
+blocking).
 .ie n .IP """EV_EMBED""" 4
 .el .IP "\f(CWEV_EMBED\fR" 4
 .IX Item "EV_EMBED"
 The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
 .ie n .IP """EV_FORK""" 4
 make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
 it).
 .IP "callback ev_cb (ev_TYPE *watcher)" 4
 .IX Item "callback ev_cb (ev_TYPE *watcher)"
 Returns the callback currently set on the watcher.
-.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
+.IP "ev_set_cb (ev_TYPE *watcher, callback)" 4
-.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
+.IX Item "ev_set_cb (ev_TYPE *watcher, callback)"
 Change the callback. You can change the callback at virtually any time
 (modulo threads).
 .IP "ev_set_priority (ev_TYPE *watcher, int priority)" 4
 .IX Item "ev_set_priority (ev_TYPE *watcher, int priority)"
 .PD 0
 .IX Subsection "WATCHER STATES"
 There are various watcher states mentioned throughout this manual \-
 active, pending and so on. In this section these states and the rules to
 transition between them will be described in more detail \- and while these
 rules might look complicated, they usually do \*(L"the right thing\*(R".
-.IP "initialiased" 4
+.IP "initialised" 4
-.IX Item "initialiased"
+.IX Item "initialised"
-Before a watcher can be registered with the event looop it has to be
+Before a watcher can be registered with the event loop it has to be
 initialised. This can be done with a call to \f(CW\*(C`ev_TYPE_init\*(C'\fR, or calls to
 \&\f(CW\*(C`ev_init\*(C'\fR followed by the watcher-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR function.
 .Sp
-In this state it is simply some block of memory that is suitable for use
+In this state it is simply some block of memory that is suitable for
-in an event loop. It can be moved around, freed, reused etc. at will.
+use in an event loop. It can be moved around, freed, reused etc. at
+will \- as long as you either keep the memory contents intact, or call
+\&\f(CW\*(C`ev_TYPE_init\*(C'\fR again.
 .IP "started/running/active" 4
 .IX Item "started/running/active"
 Once a watcher has been started with a call to \f(CW\*(C`ev_TYPE_start\*(C'\fR it becomes
 property of the event loop, and is actively waiting for events. While in
 this state it cannot be accessed (except in a few documented ways), moved,
 latter will clear any pending state the watcher might be in, regardless
 of whether it was active or not, so stopping a watcher explicitly before
 freeing it is often a good idea.
 .Sp
 While stopped (and not pending) the watcher is essentially in the
-initialised state, that is it can be reused, moved, modified in any way
+initialised state, that is, it can be reused, moved, modified in any way
-you wish.
+you wish (but when you trash the memory block, you need to \f(CW\*(C`ev_TYPE_init\*(C'\fR
+it again).
 .SS "\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0"
 .IX Subsection "WATCHER PRIORITY MODELS"
 Many event loops support \fIwatcher priorities\fR, which are usually small
 integers that influence the ordering of event callback invocation
 between watchers in some way, all else being equal.
 detecting time jumps is hard, and some inaccuracies are unavoidable (the
 monotonic clock option helps a lot here).
 .PP
 The callback is guaranteed to be invoked only \fIafter\fR its timeout has
 passed (not \fIat\fR, so on systems with very low-resolution clocks this
-might introduce a small delay). If multiple timers become ready during the
+might introduce a small delay, see \*(L"the special problem of being too
+early\*(R", below). If multiple timers become ready during the same loop
-same loop iteration then the ones with earlier time-out values are invoked
+iteration then the ones with earlier time-out values are invoked before
-before ones of the same priority with later time-out values (but this is
+ones of the same priority with later time-out values (but this is no
-no longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively).
+longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively).
 .PP
 \fIBe smart about timeouts\fR
 .IX Subsection "Be smart about timeouts"
 .PP
 Many real-world problems involve some kind of timeout, usually for error
 .Sp
 In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone,
 but remember the time of last activity, and check for a real timeout only
 within the callback:
 .Sp
-.Vb 1
+.Vb 3
+\&   ev_tstamp timeout = 60.;
 \&   ev_tstamp last_activity; // time of last activity
+\&   ev_timer timer;
 \&
 \&   static void
 \&   callback (EV_P_ ev_timer *w, int revents)
 \&   {
-\&     ev_tstamp now     = ev_now (EV_A);
+\&     // calculate when the timeout would happen
-\&     ev_tstamp timeout = last_activity + 60.;
+\&     ev_tstamp after = last_activity \- ev_now (EV_A) + timeout;
 \&
-\&     // if last_activity + 60. is older than now, we did time out
+\&     // if negative, it means we the timeout already occurred
-\&     if (timeout < now)
+\&     if (after < 0.)
 \&       {
 \&         // timeout occurred, take action
 \&       }
 \&     else
 \&       {
-\&         // callback was invoked, but there was some activity, re\-arm
+\&         // callback was invoked, but there was some recent
-\&         // the watcher to fire in last_activity + 60, which is
+\&         // activity. simply restart the timer to time out
-\&         // guaranteed to be in the future, so "again" is positive:
+\&         // after "after" seconds, which is the earliest time
-\&         w\->repeat = timeout \- now;
+\&         // the timeout can occur.
+\&         ev_timer_set (w, after, 0.);
-\&         ev_timer_again (EV_A_ w);
+\&         ev_timer_start (EV_A_ w);
 \&       }
 \&   }
 .Ve
 .Sp
-To summarise the callback: first calculate the real timeout (defined
+To summarise the callback: first calculate in how many seconds the
-as \*(L"60 seconds after the last activity\*(R"), then check if that time has
+timeout will occur (by calculating the absolute time when it would occur,
-been reached, which means something \fIdid\fR, in fact, time out. Otherwise
+\&\f(CW\*(C`last_activity + timeout\*(C'\fR, and subtracting the current time, \f(CW\*(C`ev_now
-the callback was invoked too early (\f(CW\*(C`timeout\*(C'\fR is in the future), so
+(EV_A)\*(C'\fR from that).
-re-schedule the timer to fire at that future time, to see if maybe we have
-a timeout then.
 .Sp
-Note how \f(CW\*(C`ev_timer_again\*(C'\fR is used, taking advantage of the
+If this value is negative, then we are already past the timeout, i.e. we
-\&\f(CW\*(C`ev_timer_again\*(C'\fR optimisation when the timer is already running.
+timed out, and need to do whatever is needed in this case.
+.Sp
+Otherwise, we now the earliest time at which the timeout would trigger,
+and simply start the timer with this timeout value.
+.Sp
+In other words, each time the callback is invoked it will check whether
+the timeout occurred. If not, it will simply reschedule itself to check
+again at the earliest time it could time out. Rinse. Repeat.
 .Sp
 This scheme causes more callback invocations (about one every 60 seconds
 minus half the average time between activity), but virtually no calls to
 libev to change the timeout.
 .Sp
-To start the timer, simply initialise the watcher and set \f(CW\*(C`last_activity\*(C'\fR
+To start the machinery, simply initialise the watcher and set
-to the current time (meaning we just have some activity :), then call the
+\&\f(CW\*(C`last_activity\*(C'\fR to the current time (meaning there was some activity just
-callback, which will \*(L"do the right thing\*(R" and start the timer:
+now), then call the callback, which will \*(L"do the right thing\*(R" and start
+the timer:
 .Sp
 .Vb 3
+\&   last_activity = ev_now (EV_A);
-\&   ev_init (timer, callback);
+\&   ev_init (&timer, callback);
-\&   last_activity = ev_now (loop);
+\&   callback (EV_A_ &timer, 0);
-\&   callback (loop, timer, EV_TIMER);
 .Ve
 .Sp
-And when there is some activity, simply store the current time in
+When there is some activity, simply store the current time in
 \&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all:
 .Sp
-.Vb 1
+.Vb 2
+\&   if (activity detected)
-\&   last_activity = ev_now (loop);
+\&     last_activity = ev_now (EV_A);
+.Ve
+.Sp
+When your timeout value changes, then the timeout can be changed by simply
+providing a new value, stopping the timer and calling the callback, which
+will again do the right thing (for example, time out immediately :).
+.Sp
+.Vb 3
+\&   timeout = new_value;
+\&   ev_timer_stop (EV_A_ &timer);
+\&   callback (EV_A_ &timer, 0);
 .Ve
 .Sp
 This technique is slightly more complex, but in most cases where the
 time-out is unlikely to be triggered, much more efficient.
-.Sp
-Changing the timeout is trivial as well (if it isn't hard-coded in the
-callback :) \- just change the timeout and invoke the callback, which will
-fix things for you.
 .IP "4. Wee, just use a double-linked list for your timeouts." 4
 .IX Item "4. Wee, just use a double-linked list for your timeouts."
 If there is not one request, but many thousands (millions...), all
 employing some kind of timeout with the same timeout value, then one can
 do even better:
 Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
 rather complicated, but extremely efficient, something that really pays
 off after the first million or so of active timers, i.e. it's usually
 overkill :)
 .PP
+\fIThe special problem of being too early\fR
+.IX Subsection "The special problem of being too early"
+.PP
+If you ask a timer to call your callback after three seconds, then
+you expect it to be invoked after three seconds \- but of course, this
+cannot be guaranteed to infinite precision. Less obviously, it cannot be
+guaranteed to any precision by libev \- imagine somebody suspending the
+process with a \s-1STOP\s0 signal for a few hours for example.
+.PP
+So, libev tries to invoke your callback as soon as possible \fIafter\fR the
+delay has occurred, but cannot guarantee this.
+.PP
+A less obvious failure mode is calling your callback too early: many event
+loops compare timestamps with a \*(L"elapsed delay >= requested delay\*(R", but
+this can cause your callback to be invoked much earlier than you would
+expect.
+.PP
+To see why, imagine a system with a clock that only offers full second
+resolution (think windows if you can't come up with a broken enough \s-1OS\s0
+yourself). If you schedule a one-second timer at the time 500.9, then the
+event loop will schedule your timeout to elapse at a system time of 500
+(500.9 truncated to the resolution) + 1, or 501.
+.PP
+If an event library looks at the timeout 0.1s later, it will see \*(L"501 >=
+501\*(R" and invoke the callback 0.1s after it was started, even though a
+one-second delay was requested \- this is being \*(L"too early\*(R", despite best
+intentions.
+.PP
+This is the reason why libev will never invoke the callback if the elapsed
+delay equals the requested delay, but only when the elapsed delay is
+larger than the requested delay. In the example above, libev would only invoke
+the callback at system time 502, or 1.1s after the timer was started.
+.PP
+So, while libev cannot guarantee that your callback will be invoked
+exactly when requested, it \fIcan\fR and \fIdoes\fR guarantee that the requested
+delay has actually elapsed, or in other words, it always errs on the \*(L"too
+late\*(R" side of things.
+.PP
 \fIThe special problem of time updates\fR
 .IX Subsection "The special problem of time updates"
 .PP
-Establishing the current time is a costly operation (it usually takes at
+Establishing the current time is a costly operation (it usually takes
-least two system calls): \s-1EV\s0 therefore updates its idea of the current
+at least one system call): \s-1EV\s0 therefore updates its idea of the current
 time only before and after \f(CW\*(C`ev_run\*(C'\fR collects new events, which causes a
 growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling
 lots of events in one iteration.
 .PP
 The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR
 .Ve
 .PP
 If the event loop is suspended for a long time, you can also force an
 update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update
 ()\*(C'\fR.
+.PP
+\fIThe special problem of unsynchronised clocks\fR
+.IX Subsection "The special problem of unsynchronised clocks"
+.PP
+Modern systems have a variety of clocks \- libev itself uses the normal
+\&\*(L"wall clock\*(R" clock and, if available, the monotonic clock (to avoid time
+jumps).
+.PP
+Neither of these clocks is synchronised with each other or any other clock
+on the system, so \f(CW\*(C`ev_time ()\*(C'\fR might return a considerably different time
+than \f(CW\*(C`gettimeofday ()\*(C'\fR or \f(CW\*(C`time ()\*(C'\fR. On a GNU/Linux system, for example,
+a call to \f(CW\*(C`gettimeofday\*(C'\fR might return a second count that is one higher
+than a directly following call to \f(CW\*(C`time\*(C'\fR.
+.PP
+The moral of this is to only compare libev-related timestamps with
+\&\f(CW\*(C`ev_time ()\*(C'\fR and \f(CW\*(C`ev_now ()\*(C'\fR, at least if you want better precision than
+a second or so.
+.PP
+One more problem arises due to this lack of synchronisation: if libev uses
+the system monotonic clock and you compare timestamps from \f(CW\*(C`ev_time\*(C'\fR
+or \f(CW\*(C`ev_now\*(C'\fR from when you started your timer and when your callback is
+invoked, you will find that sometimes the callback is a bit \*(L"early\*(R".
+.PP
+This is because \f(CW\*(C`ev_timer\*(C'\fRs work in real time, not wall clock time, so
+libev makes sure your callback is not invoked before the delay happened,
+\&\fImeasured according to the real time\fR, not the system clock.
+.PP
+If your timeouts are based on a physical timescale (e.g. \*(L"time out this
+connection after 100 seconds\*(R") then this shouldn't bother you as it is
+exactly the right behaviour.
+.PP
+If you want to compare wall clock/system timestamps to your timers, then
+you need to use \f(CW\*(C`ev_periodic\*(C'\fRs, as these are based on the wall clock
+time, where your comparisons will always generate correct results.
 .PP
 \fIThe special problems of suspended animation\fR
 .IX Subsection "The special problems of suspended animation"
 .PP
 When you leave the server world it is quite customary to hit machines that
 trigger at exactly 10 second intervals. If, however, your program cannot
 keep up with the timer (because it takes longer than those 10 seconds to
 do stuff) the timer will not fire more than once per event loop iteration.
 .IP "ev_timer_again (loop, ev_timer *)" 4
 .IX Item "ev_timer_again (loop, ev_timer *)"
-This will act as if the timer timed out and restart it again if it is
+This will act as if the timer timed out, and restarts it again if it is
-repeating. The exact semantics are:
+repeating. It basically works like calling \f(CW\*(C`ev_timer_stop\*(C'\fR, updating the
+timeout to the \f(CW\*(C`repeat\*(C'\fR value and calling \f(CW\*(C`ev_timer_start\*(C'\fR.
 .Sp
+The exact semantics are as in the following rules, all of which will be
+applied to the watcher:
+.RS 4
-If the timer is pending, its pending status is cleared.
+.IP "If the timer is pending, the pending status is always cleared." 4
-.Sp
+.IX Item "If the timer is pending, the pending status is always cleared."
+.PD 0
-If the timer is started but non-repeating, stop it (as if it timed out).
+.IP "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)." 4
-.Sp
+.IX Item "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)."
-If the timer is repeating, either start it if necessary (with the
+.ie n .IP "If the timer is repeating, make the ""repeat"" value the new timeout and start the timer, if necessary." 4
-\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
+.el .IP "If the timer is repeating, make the \f(CWrepeat\fR value the new timeout and start the timer, if necessary." 4
+.IX Item "If the timer is repeating, make the repeat value the new timeout and start the timer, if necessary."
+.RE
+.RS 4
+.PD
 .Sp
 This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a
 usage example.
+.RE
 .IP "ev_tstamp ev_timer_remaining (loop, ev_timer *)" 4
 .IX Item "ev_tstamp ev_timer_remaining (loop, ev_timer *)"
 Returns the remaining time until a timer fires. If the timer is active,
 then this time is relative to the current event loop time, otherwise it's
 the timeout value currently configured.
 .Sp
 Another way to think about it (for the mathematically inclined) is that
 \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
 time where \f(CW\*(C`time = offset (mod interval)\*(C'\fR, regardless of any time jumps.
 .Sp
-For numerical stability it is preferable that the \f(CW\*(C`offset\*(C'\fR value is near
+The \f(CW\*(C`interval\*(C'\fR \fI\s-1MUST\s0\fR be positive, and for numerical stability, the
-\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
+interval value should be higher than \f(CW\*(C`1/8192\*(C'\fR (which is around 100
-this value, and in fact is often specified as zero.
+microseconds) and \f(CW\*(C`offset\*(C'\fR should be higher than \f(CW0\fR and should have
+at most a similar magnitude as the current time (say, within a factor of
+ten). Typical values for offset are, in fact, \f(CW0\fR or something between
+\&\f(CW0\fR and \f(CW\*(C`interval\*(C'\fR, which is also the recommended range.
 .Sp
 Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0
 speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability
 will of course deteriorate. Libev itself tries to be exact to be about one
 millisecond (if the \s-1OS\s0 supports it and the machine is fast enough).
 .IX Subsection "The special problem of inheritance over fork/execve/pthread_create"
 .PP
 Both the signal mask (\f(CW\*(C`sigprocmask\*(C'\fR) and the signal disposition
 (\f(CW\*(C`sigaction\*(C'\fR) are unspecified after starting a signal watcher (and after
 stopping it again), that is, libev might or might not block the signal,
-and might or might not set or restore the installed signal handler.
+and might or might not set or restore the installed signal handler (but
+see \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR).
 .PP
 While this does not matter for the signal disposition (libev never
 sets signals to \f(CW\*(C`SIG_IGN\*(C'\fR, so handlers will be reset to \f(CW\*(C`SIG_DFL\*(C'\fR on
 \&\f(CW\*(C`execve\*(C'\fR), this matters for the signal mask: many programs do not expect
 certain signals to be blocked.
 .ie n .SS """ev_stat"" \- did the file attributes just change?"
 .el .SS "\f(CWev_stat\fP \- did the file attributes just change?"
 .IX Subsection "ev_stat - did the file attributes just change?"
 This watches a file system path for attribute changes. That is, it calls
 \&\f(CW\*(C`stat\*(C'\fR on that path in regular intervals (or when the \s-1OS\s0 says it changed)
-and sees if it changed compared to the last time, invoking the callback if
+and sees if it changed compared to the last time, invoking the callback
-it did.
+if it did. Starting the watcher \f(CW\*(C`stat\*(C'\fR's the file, so only changes that
+happen after the watcher has been started will be reported.
 .PP
 The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
 not exist\*(R" is a status change like any other. The condition \*(L"path does not
 exist\*(R" (or more correctly \*(L"path cannot be stat'ed\*(R") is signified by the
 \&\f(CW\*(C`st_nlink\*(C'\fR field being zero (which is otherwise always forced to be at
 Apart from keeping your process non-blocking (which is a useful
 effect on its own sometimes), idle watchers are a good place to do
 \&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the
 event loop has handled all outstanding events.
 .PP
+\fIAbusing an \f(CI\*(C`ev_idle\*(C'\fI watcher for its side-effect\fR
+.IX Subsection "Abusing an ev_idle watcher for its side-effect"
+.PP
+As long as there is at least one active idle watcher, libev will never
+sleep unnecessarily. Or in other words, it will loop as fast as possible.
+For this to work, the idle watcher doesn't need to be invoked at all \- the
+lowest priority will do.
+.PP
+This mode of operation can be useful together with an \f(CW\*(C`ev_check\*(C'\fR watcher,
+to do something on each event loop iteration \- for example to balance load
+between different connections.
+.PP
+See \*(L"Abusing an ev_check watcher for its side-effect\*(R" for a longer
+example.
+.PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_idle_init (ev_idle *, callback)" 4
 .IX Item "ev_idle_init (ev_idle *, callback)"
 Initialises and configures the idle watcher \- it has no parameters of any
 .IX Subsection "Examples"
 .PP
 Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
 callback, free it. Also, use no error checking, as usual.
 .PP
-.Vb 7
+.Vb 5
 \&   static void
 \&   idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
 \&   {
+\&     // stop the watcher
+\&     ev_idle_stop (loop, w);
+\&
+\&     // now we can free it
 \&     free (w);
+\&
 \&     // now do something you wanted to do when the program has
 \&     // no longer anything immediate to do.
 \&   }
 \&
 \&   ev_idle *idle_watcher = malloc (sizeof (ev_idle));
 \&   ev_idle_start (loop, idle_watcher);
 .Ve
 .ie n .SS """ev_prepare"" and ""ev_check"" \- customise your event loop!"
 .el .SS "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
 .IX Subsection "ev_prepare and ev_check - customise your event loop!"
-Prepare and check watchers are usually (but not always) used in pairs:
+Prepare and check watchers are often (but not always) used in pairs:
 prepare watchers get invoked before the process blocks and check watchers
 afterwards.
 .PP
 You \fImust not\fR call \f(CW\*(C`ev_run\*(C'\fR or similar functions that enter
 the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
 with priority higher than or equal to the event loop and one coroutine
 of lower priority, but only once, using idle watchers to keep the event
 loop from blocking if lower-priority coroutines are active, thus mapping
 low-priority coroutines to idle/background tasks).
 .PP
-It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
+When used for this purpose, it is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers
-priority, to ensure that they are being run before any other watchers
+highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) priority, to ensure that they are being run before
-after the poll (this doesn't matter for \f(CW\*(C`ev_prepare\*(C'\fR watchers).
+any other watchers after the poll (this doesn't matter for \f(CW\*(C`ev_prepare\*(C'\fR
+watchers).
 .PP
 Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not
 activate (\*(L"feed\*(R") events into libev. While libev fully supports this, they
 might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers did their job. As
 \&\f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other (non-libev) event
 loops those other event loops might be in an unusable state until their
 \&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
 others).
+.PP
+\fIAbusing an \f(CI\*(C`ev_check\*(C'\fI watcher for its side-effect\fR
+.IX Subsection "Abusing an ev_check watcher for its side-effect"
+.PP
+\&\f(CW\*(C`ev_check\*(C'\fR (and less often also \f(CW\*(C`ev_prepare\*(C'\fR) watchers can also be
+useful because they are called once per event loop iteration. For
+example, if you want to handle a large number of connections fairly, you
+normally only do a bit of work for each active connection, and if there
+is more work to do, you wait for the next event loop iteration, so other
+connections have a chance of making progress.
+.PP
+Using an \f(CW\*(C`ev_check\*(C'\fR watcher is almost enough: it will be called on the
+next event loop iteration. However, that isn't as soon as possible \-
+without external events, your \f(CW\*(C`ev_check\*(C'\fR watcher will not be invoked.
+.PP
+This is where \f(CW\*(C`ev_idle\*(C'\fR watchers come in handy \- all you need is a
+single global idle watcher that is active as long as you have one active
+\&\f(CW\*(C`ev_check\*(C'\fR watcher. The \f(CW\*(C`ev_idle\*(C'\fR watcher makes sure the event loop
+will not sleep, and the \f(CW\*(C`ev_check\*(C'\fR watcher makes sure a callback gets
+invoked. Neither watcher alone can do that.
 .PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_prepare_init (ev_prepare *, callback)" 4
 .IX Item "ev_prepare_init (ev_prepare *, callback)"
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
 .IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
 .PD 0
-.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
+.IP "ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)" 4
-.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
+.IX Item "ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)"
 .PD
 Configures the watcher to embed the given loop, which must be
 embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
 invoked automatically, otherwise it is the responsibility of the callback
 to invoke it (it will continue to be called until the sweep has been done,
 .ie n .SS """ev_fork"" \- the audacity to resume the event loop after a fork"
 .el .SS "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
 .IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
 Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
 whoever is a good citizen cared to tell libev about it by calling
-\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
+\&\f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the event loop blocks next
-event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
+and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, and only in the child
-and only in the child after the fork. If whoever good citizen calling
+after the fork. If whoever good citizen calling \f(CW\*(C`ev_default_fork\*(C'\fR cheats
-\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
+and calls it in the wrong process, the fork handlers will be invoked, too,
-handlers will be invoked, too, of course.
+of course.
 .PP
 \fIThe special problem of life after fork \- how is it possible?\fR
 .IX Subsection "The special problem of life after fork - how is it possible?"
 .PP
 Most uses of \f(CW\*(C`fork()\*(C'\fR consist of forking, then some simple calls to set
 \&   atexit (program_exits);
 .Ve
 .ie n .SS """ev_async"" \- how to wake up an event loop"
 .el .SS "\f(CWev_async\fP \- how to wake up an event loop"
 .IX Subsection "ev_async - how to wake up an event loop"
-In general, you cannot use an \f(CW\*(C`ev_run\*(C'\fR from multiple threads or other
+In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other
 asynchronous sources such as signal handlers (as opposed to multiple event
 loops \- those are of course safe to use in different threads).
 .PP
 Sometimes, however, you need to wake up an event loop you do not control,
 for example because it belongs to another thread. This is what \f(CW\*(C`ev_async\*(C'\fR
 it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal safe.
 .PP
 This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals,
 too, are asynchronous in nature, and signals, too, will be compressed
 (i.e. the number of callback invocations may be less than the number of
-\&\f(CW\*(C`ev_async_sent\*(C'\fR calls). In fact, you could use signal watchers as a kind
+\&\f(CW\*(C`ev_async_send\*(C'\fR calls). In fact, you could use signal watchers as a kind
 of \*(L"global async watchers\*(R" by using a watcher on an otherwise unused
 signal, and \f(CW\*(C`ev_feed_signal\*(C'\fR to signal this watcher from another thread,
 even without knowing which loop owns the signal.
-.PP
-Unlike \f(CW\*(C`ev_signal\*(C'\fR watchers, \f(CW\*(C`ev_async\*(C'\fR works with any event loop, not
-just the default loop.
 .PP
 \fIQueueing\fR
 .IX Subsection "Queueing"
 .PP
 \&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason
 kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless,
 trust me.
 .IP "ev_async_send (loop, ev_async *)" 4
 .IX Item "ev_async_send (loop, ev_async *)"
 Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds
-an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop. Unlike
+an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop, and instantly
+returns.
+.Sp
-\&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads, signal or
+Unlike \f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads,
-similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding
+signal or similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the
-section below on what exactly this means).
+embedding section below on what exactly this means).
 .Sp
 Note that, as with other watchers in libev, multiple events might get
-compressed into a single callback invocation (another way to look at this
+compressed into a single callback invocation (another way to look at
-is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered, set on \f(CW\*(C`ev_async_send\*(C'\fR,
+this is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered: they are set on
-reset when the event loop detects that).
+\&\f(CW\*(C`ev_async_send\*(C'\fR, reset when the event loop detects that).
 .Sp
-This call incurs the overhead of a system call only once per event loop
+This call incurs the overhead of at most one extra system call per event
-iteration, so while the overhead might be noticeable, it doesn't apply to
+loop iteration, if the event loop is blocked, and no syscall at all if
-repeated calls to \f(CW\*(C`ev_async_send\*(C'\fR for the same event loop.
+the event loop (or your program) is processing events. That means that
+repeated calls are basically free (there is no need to avoid calls for
+performance reasons) and that the overhead becomes smaller (typically
+zero) under load.
 .IP "bool = ev_async_pending (ev_async *)" 4
 .IX Item "bool = ev_async_pending (ev_async *)"
 Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the
 watcher but the event has not yet been processed (or even noted) by the
 event loop.
 \&   ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
 .Ve
 .IP "ev_feed_fd_event (loop, int fd, int revents)" 4
 .IX Item "ev_feed_fd_event (loop, int fd, int revents)"
 Feed an event on the given fd, as if a file descriptor backend detected
-the given events it.
+the given events.
 .IP "ev_feed_signal_event (loop, int signum)" 4
 .IX Item "ev_feed_signal_event (loop, int signum)"
 Feed an event as if the given signal occurred. See also \f(CW\*(C`ev_feed_signal\*(C'\fR,
 which is async-safe.
 .SH "COMMON OR USEFUL IDIOMS (OR BOTH)"
 \&   {
 \&     struct my_biggy big = (struct my_biggy *)
 \&       (((char *)w) \- offsetof (struct my_biggy, t2));
 \&   }
 .Ve
+.SS "\s-1AVOIDING\s0 \s-1FINISHING\s0 \s-1BEFORE\s0 \s-1RETURNING\s0"
+.IX Subsection "AVOIDING FINISHING BEFORE RETURNING"
+Often you have structures like this in event-based programs:
+.PP
+.Vb 4
+\&  callback ()
+\&  {
+\&    free (request);
+\&  }
+\&
+\&  request = start_new_request (..., callback);
+.Ve
+.PP
+The intent is to start some \*(L"lengthy\*(R" operation. The \f(CW\*(C`request\*(C'\fR could be
+used to cancel the operation, or do other things with it.
+.PP
+It's not uncommon to have code paths in \f(CW\*(C`start_new_request\*(C'\fR that
+immediately invoke the callback, for example, to report errors. Or you add
+some caching layer that finds that it can skip the lengthy aspects of the
+operation and simply invoke the callback with the result.
+.PP
+The problem here is that this will happen \fIbefore\fR \f(CW\*(C`start_new_request\*(C'\fR
+has returned, so \f(CW\*(C`request\*(C'\fR is not set.
+.PP
+Even if you pass the request by some safer means to the callback, you
+might want to do something to the request after starting it, such as
+canceling it, which probably isn't working so well when the callback has
+already been invoked.
+.PP
+A common way around all these issues is to make sure that
+\&\f(CW\*(C`start_new_request\*(C'\fR \fIalways\fR returns before the callback is invoked. If
+\&\f(CW\*(C`start_new_request\*(C'\fR immediately knows the result, it can artificially
+delay invoking the callback by using a \f(CW\*(C`prepare\*(C'\fR or \f(CW\*(C`idle\*(C'\fR watcher for
+example, or more sneakily, by reusing an existing (stopped) watcher and
+pushing it into the pending queue:
+.PP
+.Vb 2
+\&   ev_set_cb (watcher, callback);
+\&   ev_feed_event (EV_A_ watcher, 0);
+.Ve
+.PP
+This way, \f(CW\*(C`start_new_request\*(C'\fR can safely return before the callback is
+invoked, while not delaying callback invocation too much.
 .SS "\s-1MODEL/NESTED\s0 \s-1EVENT\s0 \s-1LOOP\s0 \s-1INVOCATIONS\s0 \s-1AND\s0 \s-1EXIT\s0 \s-1CONDITIONS\s0"
 .IX Subsection "MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS"
 Often (especially in \s-1GUI\s0 toolkits) there are places where you have
 \&\fImodal\fR interaction, which is most easily implemented by recursively
 invoking \f(CW\*(C`ev_run\*(C'\fR.
 .PP
 This brings the problem of exiting \- a callback might want to finish the
 main \f(CW\*(C`ev_run\*(C'\fR call, but not the nested one (e.g. user clicked \*(L"Quit\*(R", but
 a modal \*(L"Are you sure?\*(R" dialog is still waiting), or just the nested one
 and not the main one (e.g. user clocked \*(L"Ok\*(R" in a modal dialog), or some
-other combination: In these cases, \f(CW\*(C`ev_break\*(C'\fR will not work alone.
+other combination: In these cases, a simple \f(CW\*(C`ev_break\*(C'\fR will not work.
 .PP
 The solution is to maintain \*(L"break this loop\*(R" variable for each \f(CW\*(C`ev_run\*(C'\fR
 invocation, and use a loop around \f(CW\*(C`ev_run\*(C'\fR until the condition is
 triggered, using \f(CW\*(C`EVRUN_ONCE\*(C'\fR:
 .PP
 \&   int exit_main_loop = 0;
 \&
 \&   while (!exit_main_loop)
 \&     ev_run (EV_DEFAULT_ EVRUN_ONCE);
 \&
-\&   // in a model watcher
+\&   // in a modal watcher
 \&   int exit_nested_loop = 0;
 \&
 \&   while (!exit_nested_loop)
 \&     ev_run (EV_A_ EVRUN_ONCE);
 .Ve
 \&      // now associate this with the loop
 \&      ev_set_userdata (EV_A_ u);
 \&      ev_set_invoke_pending_cb (EV_A_ l_invoke);
 \&      ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
 \&
-\&      // then create the thread running ev_loop
+\&      // then create the thread running ev_run
 \&      pthread_create (&u\->tid, 0, l_run, EV_A);
 \&   }
 .Ve
 .PP
 The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used
 .PP
 .Vb 6
 \&   void
 \&   wait_for_event (ev_watcher *w)
 \&   {
-\&     ev_cb_set (w) = current_coro;
+\&     ev_set_cb (w, current_coro);
 \&     switch_to (libev_coro);
 \&   }
 .Ve
 .PP
 That basically suspends the coroutine inside \f(CW\*(C`wait_for_event\*(C'\fR and
 continues the libev coroutine, which, when appropriate, switches back to
-this or any other coroutine. I am sure if you sue this your own :)
+this or any other coroutine.
 .PP
 You can do similar tricks if you have, say, threads with an event queue \-
 instead of storing a coroutine, you store the queue object and instead of
 switching to a coroutine, you push the watcher onto the queue and notify
 any waiters.
 .PP
-To embed libev, see \s-1EMBEDDING\s0, but in short, it's easiest to create two
+To embed libev, see \*(L"\s-1EMBEDDING\s0\*(R", but in short, it's easiest to create two
 files, \fImy_ev.h\fR and \fImy_ev.c\fR that include the respective libev files:
 .PP
 .Vb 4
 \&   // my_ev.h
 \&   #define EV_CB_DECLARE(type)   struct my_coro *cb;
 .IP "\(bu" 4
 The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need
 to use the libev header file and library.
 .SH "\*(C+ SUPPORT"
 .IX Header " SUPPORT"
+.SS "C \s-1API\s0"
+.IX Subsection "C API"
+The normal C \s-1API\s0 should work fine when used from \*(C+: both ev.h and the
+libev sources can be compiled as \*(C+. Therefore, code that uses the C \s-1API\s0
+will work fine.
+.PP
+Proper exception specifications might have to be added to callbacks passed
+to libev: exceptions may be thrown only from watcher callbacks, all
+other callbacks (allocator, syserr, loop acquire/release and periodic
+reschedule callbacks) must not throw exceptions, and might need a \f(CW\*(C`throw
+()\*(C'\fR specification. If you have code that needs to be compiled as both C
+and \*(C+ you can use the \f(CW\*(C`EV_THROW\*(C'\fR macro for this:
+.PP
+.Vb 6
+\&   static void
+\&   fatal_error (const char *msg) EV_THROW
+\&   {
+\&     perror (msg);
+\&     abort ();
+\&   }
+\&
+\&   ...
+\&   ev_set_syserr_cb (fatal_error);
+.Ve
+.PP
+The only \s-1API\s0 functions that can currently throw exceptions are \f(CW\*(C`ev_run\*(C'\fR,
+\&\f(CW\*(C`ev_invoke\*(C'\fR, \f(CW\*(C`ev_invoke_pending\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR (the latter
+because it runs cleanup watchers).
+.PP
+Throwing exceptions in watcher callbacks is only supported if libev itself
+is compiled with a \*(C+ compiler or your C and \*(C+ environments allow
+throwing exceptions through C libraries (most do).
+.SS "\*(C+ \s-1API\s0"
+.IX Subsection " API"
 Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
 you to use some convenience methods to start/stop watchers and also change
 the callback model to a model using method callbacks on objects.
 .PP
 To use it,
 Currently, functions, static and non-static member functions and classes
 with \f(CW\*(C`operator ()\*(C'\fR can be used as callbacks. Other types should be easy
 to add as long as they only need one additional pointer for context. If
 you need support for other types of functors please contact the author
 (preferably after implementing it).
+.PP
+For all this to work, your \*(C+ compiler either has to use the same calling
+conventions as your C compiler (for static member functions), or you have
+to embed libev and compile libev itself as \*(C+.
 .PP
 Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
 .ie n .IP """ev::READ"", ""ev::WRITE"" etc." 4
 .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
 .IX Item "ev::READ, ev::WRITE etc."
 .el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
 .IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
 For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
 the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
 which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
-defines by many implementations.
+defined by many implementations.
 .Sp
 All of those classes have these methods:
 .RS 4
 .IP "ev::TYPE::TYPE ()" 4
 .IX Item "ev::TYPE::TYPE ()"
 .IX Item "w->set (loop)"
 Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
 do this when the watcher is inactive (and not pending either).
 .IP "w\->set ([arguments])" 4
 .IX Item "w->set ([arguments])"
-Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same arguments. Either this
+Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR (except for \f(CW\*(C`ev::embed\*(C'\fR watchers>),
-method or a suitable start method must be called at least once. Unlike the
+with the same arguments. Either this method or a suitable start method
-C counterpart, an active watcher gets automatically stopped and restarted
+must be called at least once. Unlike the C counterpart, an active watcher
-when reconfiguring it with this method.
+gets automatically stopped and restarted when reconfiguring it with this
+method.
+.Sp
+For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid
+clashing with the \f(CW\*(C`set (loop)\*(C'\fR method.
 .IP "w\->start ()" 4
 .IX Item "w->start ()"
 Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
 constructor already stores the event loop.
 .IP "w\->start ([arguments])" 4
 .PP
 .Vb 5
 \&   class myclass
 \&   {
 \&     ev::io   io  ; void io_cb   (ev::io   &w, int revents);
-\&     ev::io2  io2 ; void io2_cb  (ev::io   &w, int revents);
+\&     ev::io   io2 ; void io2_cb  (ev::io   &w, int revents);
 \&     ev::idle idle; void idle_cb (ev::idle &w, int revents);
 \&
 \&     myclass (int fd)
 \&     {
 \&       io  .set <myclass, &myclass::io_cb  > (this);
 Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR
 makes rev work even on mingw.
 .IP "Haskell" 4
 .IX Item "Haskell"
 A haskell binding to libev is available at
-<http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev>.
+http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev <http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
 .IP "D" 4
 .IX Item "D"
 Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to
-be found at <http://proj.llucax.com.ar/wiki/evd>.
+be found at <http://www.llucax.com.ar/proj/ev.d/index.html>.
 .IP "Ocaml" 4
 .IX Item "Ocaml"
 Erkki Seppala has written Ocaml bindings for libev, to be found at
-<http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/>.
+http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/ <http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
 .IP "Lua" 4
 .IX Item "Lua"
 Brian Maher has written a partial interface to libev for lua (at the
 time of this writing, only \f(CW\*(C`ev_io\*(C'\fR and \f(CW\*(C`ev_timer\*(C'\fR), to be found at
-<http://github.com/brimworks/lua\-ev>.
+http://github.com/brimworks/lua\-ev <http://github.com/brimworks/lua-ev>.
+.IP "Javascript" 4
+.IX Item "Javascript"
+Node.js (<http://nodejs.org>) uses libev as the underlying event library.
+.IP "Others" 4
+.IX Item "Others"
+There are others, and I stopped counting.
 .SH "MACRO MAGIC"
 .IX Header "MACRO MAGIC"
 Libev can be compiled with a variety of options, the most fundamental
 of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
 functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
 suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
 .ie n .IP """EV_DEFAULT"", ""EV_DEFAULT_""" 4
 .el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
 .IX Item "EV_DEFAULT, EV_DEFAULT_"
 Similar to the other two macros, this gives you the value of the default
-loop, if multiple loops are supported (\*(L"ev loop default\*(R").
+loop, if multiple loops are supported (\*(L"ev loop default\*(R"). The default loop
+will be initialised if it isn't already initialised.
+.Sp
+For non-multiplicity builds, these macros do nothing, so you always have
+to initialise the loop somewhere.
 .ie n .IP """EV_DEFAULT_UC"", ""EV_DEFAULT_UC_""" 4
 .el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4
 .IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_"
 Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the
 default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour
 supported). It will also not define any of the structs usually found in
 \&\fIevent.h\fR that are not directly supported by the libev core alone.
 .Sp
 In standalone mode, libev will still try to automatically deduce the
 configuration, but has to be more conservative.
+.IP "\s-1EV_USE_FLOOR\s0" 4
+.IX Item "EV_USE_FLOOR"
+If defined to be \f(CW1\fR, libev will use the \f(CW\*(C`floor ()\*(C'\fR function for its
+periodic reschedule calculations, otherwise libev will fall back on a
+portable (slower) implementation. If you enable this, you usually have to
+link against libm or something equivalent. Enabling this when the \f(CW\*(C`floor\*(C'\fR
+function is not available will fail, so the safe default is to not enable
+this.
 .IP "\s-1EV_USE_MONOTONIC\s0" 4
 .IX Item "EV_USE_MONOTONIC"
 If defined to be \f(CW1\fR, libev will try to detect the availability of the
 monotonic clock option at both compile time and runtime. Otherwise no
 use of the monotonic clock option will be attempted. If you enable this,
 .IX Item "EV_WIN32_CLOSE_FD(fd)"
 If programs implement their own fd to handle mapping on win32, then this
 macro can be used to override the \f(CW\*(C`close\*(C'\fR function, useful to unregister
 file descriptors again. Note that the replacement function has to close
 the underlying \s-1OS\s0 handle.
+.IP "\s-1EV_USE_WSASOCKET\s0" 4
+.IX Item "EV_USE_WSASOCKET"
+If defined to be \f(CW1\fR, libev will use \f(CW\*(C`WSASocket\*(C'\fR to create its internal
+communication socket, which works better in some environments. Otherwise,
+the normal \f(CW\*(C`socket\*(C'\fR function will be used, which works better in other
+environments.
 .IP "\s-1EV_USE_POLL\s0" 4
 .IX Item "EV_USE_POLL"
 If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
 backend. Otherwise it will be enabled on non\-win32 platforms. It
 takes precedence over select.
 .IX Item "EV_USE_INOTIFY"
 If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
 interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
 be detected at runtime. If undefined, it will be enabled if the headers
 indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
+.IP "\s-1EV_NO_SMP\s0" 4
+.IX Item "EV_NO_SMP"
+If defined to be \f(CW1\fR, libev will assume that memory is always coherent
+between threads, that is, threads can be used, but threads never run on
+different cpus (or different cpu cores). This reduces dependencies
+and makes libev faster.
+.IP "\s-1EV_NO_THREADS\s0" 4
+.IX Item "EV_NO_THREADS"
+If defined to be \f(CW1\fR, libev will assume that it will never be called from
+different threads (that includes signal handlers), which is a stronger
+assumption than \f(CW\*(C`EV_NO_SMP\*(C'\fR, above. This reduces dependencies and makes
+libev faster.
 .IP "\s-1EV_ATOMIC_T\s0" 4
 .IX Item "EV_ATOMIC_T"
 Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose
-access is atomic with respect to other threads or signal contexts. No such
+access is atomic with respect to other threads or signal contexts. No
-type is easily found in the C language, so you can provide your own type
+such type is easily found in the C language, so you can provide your own
-that you know is safe for your purposes. It is used both for signal handler \*(L"locking\*(R"
+type that you know is safe for your purposes. It is used both for signal
-as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR watchers.
+handler \*(L"locking\*(R" as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR
+watchers.
 .Sp
 In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR
 (from \fIsignal.h\fR), which is usually good enough on most platforms.
 .IP "\s-1EV_H\s0 (h)" 4
 .IX Item "EV_H (h)"
 If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
 will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
 additional independent event loops. Otherwise there will be no support
 for multiple event loops and there is no first event loop pointer
 argument. Instead, all functions act on the single default loop.
+.Sp
+Note that \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR will no longer provide a
+default loop when multiplicity is switched off \- you always have to
+initialise the loop manually in this case.
 .IP "\s-1EV_MINPRI\s0" 4
 .IX Item "EV_MINPRI"
 .PD 0
 .IP "\s-1EV_MAXPRI\s0" 4
 .IX Item "EV_MAXPRI"
 \&   #define EV_CHILD_ENABLE 1
 \&   #define EV_ASYNC_ENABLE 1
 .Ve
 .Sp
 The actual value is a bitset, it can be a combination of the following
-values:
+values (by default, all of these are enabled):
 .RS 4
 .ie n .IP "1 \- faster/larger code" 4
 .el .IP "\f(CW1\fR \- faster/larger code" 4
 .IX Item "1 - faster/larger code"
 Use larger code to speed up some operations.
 code size by roughly 30% on amd64).
 .Sp
 When optimising for size, use of compiler flags such as \f(CW\*(C`\-Os\*(C'\fR with
 gcc is recommended, as well as \f(CW\*(C`\-DNDEBUG\*(C'\fR, as libev contains a number of
 assertions.
+.Sp
+The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler
+(e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR).
 .ie n .IP "2 \- faster/larger data structures" 4
 .el .IP "\f(CW2\fR \- faster/larger data structures" 4
 .IX Item "2 - faster/larger data structures"
 Replaces the small 2\-heap for timer management by a faster 4\-heap, larger
 hash table sizes and so on. This will usually further increase code size
 and can additionally have an effect on the size of data structures at
 runtime.
+.Sp
+The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler
+(e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR).
 .ie n .IP "4 \- full \s-1API\s0 configuration" 4
 .el .IP "\f(CW4\fR \- full \s-1API\s0 configuration" 4
 .IX Item "4 - full API configuration"
 This enables priorities (sets \f(CW\*(C`EV_MAXPRI\*(C'\fR=2 and \f(CW\*(C`EV_MINPRI\*(C'\fR=\-2), and
 enables multiplicity (\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR=1).
 With an intelligent-enough linker (gcc+binutils are intelligent enough
 when you use \f(CW\*(C`\-Wl,\-\-gc\-sections \-ffunction\-sections\*(C'\fR) functions unused by
 your program might be left out as well \- a binary starting a timer and an
 I/O watcher then might come out at only 5Kb.
 .RE
+.IP "\s-1EV_API_STATIC\s0" 4
+.IX Item "EV_API_STATIC"
+If this symbol is defined (by default it is not), then all identifiers
+will have static linkage. This means that libev will not export any
+identifiers, and you cannot link against libev anymore. This can be useful
+when you embed libev, only want to use libev functions in a single file,
+and do not want its identifiers to be visible.
+.Sp
+To use this, define \f(CW\*(C`EV_API_STATIC\*(C'\fR and include \fIev.c\fR in the file that
+wants to use libev.
+.Sp
+This option only works when libev is compiled with a C compiler, as \*(C+
+doesn't support the required declaration syntax.
 .IP "\s-1EV_AVOID_STDIO\s0" 4
 .IX Item "EV_AVOID_STDIO"
 If this is set to \f(CW1\fR at compiletime, then libev will avoid using stdio
 functions (printf, scanf, perror etc.). This will increase the code size
 somewhat, but if your program doesn't otherwise depend on stdio and your
 requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0
 model. Libev still offers limited functionality on this platform in
 the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket
 descriptors. This only applies when using Win32 natively, not when using
 e.g. cygwin. Actually, it only applies to the microsofts own compilers,
-as every compielr comes with a slightly differently broken/incompatible
+as every compiler comes with a slightly differently broken/incompatible
 environment.
 .PP
 Lifting these limitations would basically require the full
 re-implementation of the I/O system. If you are into this kind of thing,
 then note that glib does exactly that for you in a very portable way (note
 thread\*(R" or will block signals process-wide, both behaviours would
 be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and
 \&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however.
 .Sp
 The most portable way to handle signals is to block signals in all threads
-except the initial one, and run the default loop in the initial thread as
+except the initial one, and run the signal handling loop in the initial
-well.
+thread as well.
 .ie n .IP """long"" must be large enough for common memory allocation sizes" 4
 .el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4
 .IX Item "long must be large enough for common memory allocation sizes"
 To improve portability and simplify its \s-1API\s0, libev uses \f(CW\*(C`long\*(C'\fR internally
 instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On non-POSIX
 .IX Item "double must hold a time value in seconds with enough accuracy"
 The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to
 have at least 51 bits of mantissa (and 9 bits of exponent), which is
 good enough for at least into the year 4000 with millisecond accuracy
 (the design goal for libev). This requirement is overfulfilled by
-implementations using \s-1IEEE\s0 754, which is basically all existing ones. With
+implementations using \s-1IEEE\s0 754, which is basically all existing ones.
+.Sp
-\&\s-1IEEE\s0 754 doubles, you get microsecond accuracy until at least 2200.
+With \s-1IEEE\s0 754 doubles, you get microsecond accuracy until at least the
+year 2255 (and millisecond accuracy till the year 287396 \- by then, libev
+is either obsolete or somebody patched it to use \f(CW\*(C`long double\*(C'\fR or
+something like that, just kidding).
 .PP
 If you know of other additional requirements drop me a note.
 .SH "ALGORITHMIC COMPLEXITIES"
 .IX Header "ALGORITHMIC COMPLEXITIES"
 In this section the complexities of (many of) the algorithms used inside
 .IX Item "Processing ev_async_send: O(number_of_async_watchers)"
 .IP "Processing signals: O(max_signal_number)" 4
 .IX Item "Processing signals: O(max_signal_number)"
 .PD
 Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR
-calls in the current loop iteration. Checking for async and signal events
+calls in the current loop iteration and the loop is currently
+blocked. Checking for async and signal events involves iterating over all
-involves iterating over all running async watchers or all signal numbers.
+running async watchers or all signal numbers.
 .SH "PORTING FROM LIBEV 3.X TO 4.X"
 .IX Header "PORTING FROM LIBEV 3.X TO 4.X"
 The major version 4 introduced some incompatible changes to the \s-1API\s0.
 .PP
 At the moment, the \f(CW\*(C`ev.h\*(C'\fR header file provides compatibility definitions
 new \s-1API\s0 early than late.
 .ie n .IP """EV_COMPAT3"" backwards compatibility mechanism" 4
 .el .IP "\f(CWEV_COMPAT3\fR backwards compatibility mechanism" 4
 .IX Item "EV_COMPAT3 backwards compatibility mechanism"
 The backward compatibility mechanism can be controlled by
-\&\f(CW\*(C`EV_COMPAT3\*(C'\fR. See \*(L"\s-1MACROS\s0\*(R" in \s-1PREPROCESSOR\s0 \s-1SYMBOLS\s0 in the \s-1EMBEDDING\s0
+\&\f(CW\*(C`EV_COMPAT3\*(C'\fR. See \*(L"\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0\*(R" in the \*(L"\s-1EMBEDDING\s0\*(R"
 section.
 .ie n .IP """ev_default_destroy"" and ""ev_default_fork"" have been removed" 4
 .el .IP "\f(CWev_default_destroy\fR and \f(CWev_default_fork\fR have been removed" 4
 .IX Item "ev_default_destroy and ev_default_fork have been removed"
 These calls can be replaced easily by their \f(CW\*(C`ev_loop_xxx\*(C'\fR counterparts:
 .IX Item "real time"
 The physical time that is observed. It is apparently strictly monotonic :)
 .IP "wall-clock time" 4
 .IX Item "wall-clock time"
 The time and date as shown on clocks. Unlike real time, it can actually
-be wrong and jump forwards and backwards, e.g. when the you adjust your
+be wrong and jump forwards and backwards, e.g. when you adjust your
 clock.
 .IP "watcher" 4
 .IX Item "watcher"
 A data structure that describes interest in certain events. Watchers need
 to be started (attached to an event loop) before they can receive events.
 .SH "AUTHOR"
 .IX Header "AUTHOR"
 Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
-Magnusson and Emanuele Giaquinta.
+Magnusson and Emanuele Giaquinta, and minor corrections by many others.

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Comparing libev/ev.3 (file contents): Revision 1.85 by root, Tue Jan 11 13:45:28 2011 UTC vs. Revision 1.99 by root, Mon Jun 10 00:14:23 2013 UTC

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Comparing libev/ev.3 (file contents):
Revision 1.85 by root, Tue Jan 11 13:45:28 2011 UTC vs.
Revision 1.99 by root, Mon Jun 10 00:14:23 2013 UTC