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

Comparing libev/ev.pod (file contents):
Revision 1.159 by root, Thu May 22 02:44:57 2008 UTC vs.
Revision 1.161 by root, Sat May 24 03:08:03 2008 UTC

 Libev represents time as a single floating point number, representing the
 (fractional) number of seconds since the (POSIX) epoch (somewhere near
 the beginning of 1970, details are complicated, don't ask). This type is
 called C<ev_tstamp>, which is what you should use too. It usually aliases
 to the C<double> type in C, and when you need to do any calculations on
-it, you should treat it as some floatingpoint value. Unlike the name
+it, you should treat it as some floating point value. Unlike the name
 component C<stamp> might indicate, it is also used for time differences
 throughout libev.
+=head1 ERROR HANDLING
+Libev knows three classes of errors: operating system errors, usage errors
+and internal errors (bugs).
+When libev catches an operating system error it cannot handle (for example
+a system call indicating a condition libev cannot fix), it calls the callback
+set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
+abort. The default is to print a diagnostic message and to call C<abort
+()>.
+When libev detects a usage error such as a negative timer interval, then
+it will print a diagnostic message and abort (via the C<assert> mechanism,
+so C<NDEBUG> will disable this checking): these are programming errors in
+the libev caller and need to be fixed there.
+Libev also has a few internal error-checking C<assert>ions, and also has
+extensive consistency checking code. These do not trigger under normal
+circumstances, as they indicate either a bug in libev or worse.
 =head1 GLOBAL FUNCTIONS
 These functions can be called anytime, even before initialising the
 library in any way.
 =item ev_sleep (ev_tstamp interval)
 Sleep for the given interval: The current thread will be blocked until
 either it is interrupted or the given time interval has passed. Basically
-this is a subsecond-resolution C<sleep ()>.
+this is a sub-second-resolution C<sleep ()>.
 =item int ev_version_major ()
 =item int ev_version_minor ()
 =item unsigned int ev_recommended_backends ()
 Return the set of all backends compiled into this binary of libev and also
 recommended for this platform. This set is often smaller than the one
 returned by C<ev_supported_backends>, as for example kqueue is broken on
-most BSDs and will not be autodetected unless you explicitly request it
+most BSDs and will not be auto-detected unless you explicitly request it
 (assuming you know what you are doing). This is the set of backends that
 libev will probe for if you specify no backends explicitly.
 =item unsigned int ev_embeddable_backends ()
    ...
    ev_set_allocator (persistent_realloc);
 =item ev_set_syserr_cb (void (*cb)(const char *msg));
-Set the callback function to call on a retryable syscall error (such
+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 sitution, no
+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
 requested operation, or, if the condition doesn't go away, do bad stuff
 (such as abort).
 Example: This is basically the same thing that libev does internally, too.
 from multiple threads, you have to lock (note also that this is unlikely,
 as loops cannot bes hared easily between threads anyway).
 The default loop is the only loop that can handle C<ev_signal> and
 C<ev_child> watchers, and to do this, it always registers a handler
-for C<SIGCHLD>. If this is a problem for your app you can either
+for C<SIGCHLD>. If this is a problem for your application you can either
 create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
 can simply overwrite the C<SIGCHLD> signal handler I<after> calling
 C<ev_default_init>.
 The flags argument can be used to specify special behaviour or specific
 The default flags value. Use this if you have no clue (it's the right
 thing, believe me).
 =item C<EVFLAG_NOENV>
-If this flag bit is ored into the flag value (or the program runs setuid
+If this flag bit is or'ed into the flag value (or the program runs setuid
 or setgid) then libev will I<not> look at the environment variable
 C<LIBEV_FLAGS>. 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
 around bugs.
 This works by calling C<getpid ()> on every iteration of the loop,
 and thus this might slow down your event loop if you do a lot of loop
 iterations and little real work, but is usually not noticeable (on my
 GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
-without a syscall and thus I<very> fast, but my GNU/Linux system also has
+without a system call and thus I<very> fast, but my GNU/Linux system also has
 C<pthread_atfork> which is even faster).
 The big advantage of this flag is that you can forget about fork (and
 forget about forgetting to tell libev about forking) when you use this
 flag.
-This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
+This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
 environment variable.
 =item C<EVBACKEND_SELECT>  (value 1, portable select backend)
 This is your standard select(2) backend. Not I<completely> standard, as
 but if that fails, expect a fairly low limit on the number of fds when
 using this backend. It doesn't scale too well (O(highest_fd)), but its
 usually the fastest backend for a low number of (low-numbered :) fds.
 To get good performance out of this backend you need a high amount of
-parallelity (most of the file descriptors should be busy). If you are
+parallelism (most of the file descriptors should be busy). If you are
 writing a server, you should C<accept ()> in a loop to accept as many
 connections as possible during one iteration. You might also want to have
 a look at C<ev_set_io_collect_interval ()> to increase the amount of
 readiness notifications you get per iteration.
 For few fds, this backend is a bit little slower than poll and select,
 but it scales phenomenally better. While poll and select usually scale
 like O(total_fds) where n is the total number of fds (or the highest fd),
 epoll scales either O(1) or O(active_fds). The epoll design has a number
 of shortcomings, such as silently dropping events in some hard-to-detect
-cases and requiring a syscall per fd change, no fork support and bad
+cases and requiring a system call per fd change, no fork support and bad
 support for dup.
 While stopping, setting and starting an I/O watcher in the same iteration
-will result in some caching, there is still a syscall per such incident
+will result in some caching, there is still a system call per such incident
 (because the fd could point to a different file description now), so its
 best to avoid that. Also, C<dup ()>'ed file descriptors might not work
 very well if you register events for both fds.
 Please note that epoll sometimes generates spurious notifications, so you
 Best performance from this backend is achieved by not unregistering all
 watchers for a file descriptor until it has been closed, if possible, i.e.
 keep at least one watcher active per fd at all times.
-While nominally embeddeble in other event loops, this feature is broken in
+While nominally embeddable in other event loops, this feature is broken in
 all kernel versions tested so far.
 =item C<EVBACKEND_KQUEUE>  (value 8, most BSD clones)
 Kqueue deserves special mention, as at the time of this writing, it
 was broken on all BSDs except NetBSD (usually it doesn't work reliably
 with anything but sockets and pipes, except on Darwin, where of course
-it's completely useless). For this reason it's not being "autodetected"
+it's completely useless). For this reason it's not being "auto-detected"
 unless you explicitly specify it explicitly in the flags (i.e. using
 C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
 system like NetBSD.
 You still can embed kqueue into a normal poll or select backend and use it
 the target platform). See C<ev_embed> watchers for more info.
 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 syscall as with C<EVBACKEND_EPOLL>, it still adds up to
+cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
 two event changes per incident, support for C<fork ()> is very bad and it
 drops fds silently in similarly hard-to-detect cases.
 This backend usually performs well under most conditions.
 =item C<EVBACKEND_PORT>    (value 32, Solaris 10)
 This uses the Solaris 10 event port mechanism. As with everything on Solaris,
 it's really slow, but it still scales very well (O(active_fds)).
-Please note that solaris event ports can deliver a lot of spurious
+Please note that Solaris event ports can deliver a lot of spurious
 notifications, so you need to use non-blocking I/O or other means to avoid
 blocking when no data (or space) is available.
 While this backend scales well, it requires one system call per active
 file descriptor per loop iteration. For small and medium numbers of file
 It is definitely not recommended to use this flag.
 =back
-If one or more of these are ored into the flags value, then only these
+If one or more of these are or'ed into the flags value, then only these
 backends will be tried (in the reverse order as listed here). If none are
 specified, all backends in C<ev_recommended_backends ()> will be tried.
 The most typical usage is like this:
 =item ev_default_destroy ()
 Destroys the default loop again (frees all memory and kernel state
 etc.). None of the active event watchers will be stopped in the normal
 sense, so e.g. C<ev_is_active> might still return true. It is your
-responsibility to either stop all watchers cleanly yoursef I<before>
+responsibility to either stop all watchers cleanly yourself I<before>
 calling this function, or cope with the fact afterwards (which is usually
 the easiest thing, you can just ignore the watchers and/or C<free ()> them
 for example).
 Note that certain global state, such as signal state, will not be freed by
 A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
 those events and any outstanding ones, but will not block your process in
 case there are no events and will return after one iteration of the loop.
 A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
-neccessary) and will handle those and any outstanding ones. It will block
+necessary) and will handle those and any outstanding ones. It will block
 your process until at least one new event arrives, and will return after
 one iteration of the loop. This is useful if you are waiting for some
 external event in conjunction with something not expressible using other
 libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
 usually a better approach for this kind of thing.
 to spend more time collecting timeouts, at the expense of increased
 latency (the watcher callback will be called later). C<ev_io> watchers
 will not be affected. Setting this to a non-null value will not introduce
 any overhead in libev.
-Many (busy) programs can usually benefit by setting the io collect
+Many (busy) programs can usually benefit by setting the I/O collect
 interval to a value near C<0.1> or so, which is often enough for
 interactive servers (of course not for games), likewise for timeouts. It
 usually doesn't make much sense to set it to a lower value than C<0.01>,
-as this approsaches the timing granularity of most systems.
+as this approaches the timing granularity of most systems.
 =item ev_loop_verify (loop)
 This function only does something when C<EV_VERIFY> support has been
 compiled in. It tries to go through all internal structures and checks
 watcher structures (and it is usually a bad idea to do this on the stack,
 although this can sometimes be quite valid).
 Each watcher structure must be initialised by a call to C<ev_init
 (watcher *, callback)>, which expects a callback to be provided. This
-callback gets invoked each time the event occurs (or, in the case of io
+callback gets invoked each time the event occurs (or, in the case of I/O
 watchers, each time the event loop detects that the file descriptor given
 is readable and/or writable).
 Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
 with arguments specific to this watcher type. There is also a macro
 The given async watcher has been asynchronously notified (see C<ev_async>).
 =item C<EV_ERROR>
-An unspecified error has occured, the watcher has been stopped. This might
+An unspecified error has occurred, the watcher has been stopped. This might
 happen because the watcher could not be properly started because libev
 ran out of memory, a file descriptor was found to be closed or any other
 problem. You best act on it by reporting the problem and somehow coping
 with the watcher being stopped.
 Libev will usually signal a few "dummy" events together with an error,
 for example it might indicate that a fd is readable or writable, and if
 your callbacks is well-written it can just attempt the operation and cope
-with the error from read() or write(). This will not work in multithreaded
+with the error from read() or write(). This will not work in multi-threaded
 programs, though, so beware.
 =back
 =head2 GENERIC WATCHER FUNCTIONS
 Although some watcher types do not have type-specific arguments
 (e.g. C<ev_prepare>) you still need to call its C<set> macro.
 =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
-This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
+This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
-calls into a single call. This is the most convinient method to initialise
+calls into a single call. This is the most convenient method to initialise
 a watcher. The same limitations apply, of course.
 =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
 Starts (activates) the given watcher. Only active watchers will receive
 Another thing you have to watch out for is that it is quite easy to
 receive "spurious" readiness notifications, that is your callback might
 be called with C<EV_READ> but a subsequent C<read>(2) will actually block
 because there is no data. Not only are some backends known to create a
-lot of those (for example solaris ports), it is very easy to get into
+lot of those (for example Solaris ports), it is very easy to get into
 this situation even with a relatively standard program structure. Thus
 it is best to always use non-blocking I/O: An extra C<read>(2) returning
 C<EAGAIN> is far preferable to a program hanging until some data arrives.
 If you cannot run the fd in non-blocking mode (for example you should not
-play around with an Xlib connection), then you have to seperately re-test
+play around with an Xlib connection), then you have to separately re-test
 whether a file descriptor is really ready with a known-to-be good interface
 such as poll (fortunately in our Xlib example, Xlib already does this on
 its own, so its quite safe to use).
 =head3 The special problem of disappearing file descriptors
 =item ev_io_init (ev_io *, callback, int fd, int events)
 =item ev_io_set (ev_io *, int fd, int events)
 Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
-rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
+receive events for and events is either C<EV_READ>, C<EV_WRITE> or
 C<EV_READ | EV_WRITE> to receive the given events.
 =item int fd [read-only]
 The file descriptor being watched.
 Timer watchers are simple relative timers that generate an event after a
 given time, and optionally repeating in regular intervals after that.
 The timers are based on real time, that is, if you register an event that
-times out after an hour and you reset your system clock to january last
+times out after an hour and you reset your system clock to January last
 year, it will still time out after (roughly) and hour. "Roughly" because
 detecting time jumps is hard, and some inaccuracies are unavoidable (the
 monotonic clock option helps a lot here).
 The relative timeouts are calculated relative to the C<ev_now ()>
 you suspect event processing to be delayed and you I<need> to base the timeout
 on the current time, use something like this to adjust for this:
    ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
-The callback is guarenteed to be invoked only after its timeout has passed,
+The callback is guaranteed to be invoked only after its timeout has passed,
 but if multiple timers become ready during the same loop iteration then
 order of execution is undefined.
 =head3 Watcher-Specific Functions and Data Members
 This will act as if the timer timed out and restart it again if it is
 repeating. The exact semantics are:
 If the timer is pending, its pending status is cleared.
-If the timer is started but nonrepeating, stop it (as if it timed out).
+If the timer is started but non-repeating, stop it (as if it timed out).
 If the timer is repeating, either start it if necessary (with the
 C<repeat> value), or reset the running timer to the C<repeat> value.
 This sounds a bit complicated, but here is a useful and typical
-example: Imagine you have a tcp connection and you want a so-called idle
+example: Imagine you have a TCP connection and you want a so-called idle
 timeout, that is, you want to be called when there have been, say, 60
 seconds of inactivity on the socket. The easiest way to do this is to
 configure an C<ev_timer> with a C<repeat> value of C<60> and then call
 C<ev_timer_again> each time you successfully read or write some data. If
 you go into an idle state where you do not expect data to travel on the
 Periodic watchers are also timers of a kind, but they are very versatile
 (and unfortunately a bit complex).
 Unlike C<ev_timer>'s, they are not based on real time (or relative time)
-but on wallclock time (absolute time). You can tell a periodic watcher
+but on wall clock time (absolute time). You can tell a periodic watcher
 to trigger after some specific point in time. For example, if you tell a
-periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
+periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
 + 10.>, that is, an absolute time not a delay) and then reset your system
-clock to january of the previous year, then it will take more than year
+clock to January of the previous year, then it will take more than year
 to trigger the event (unlike an C<ev_timer>, which would still trigger
 roughly 10 seconds later as it uses a relative timeout).
 C<ev_periodic>s can also be used to implement vastly more complex timers,
 such as triggering an event on each "midnight, local time", or other
 complicated, rules.
-As with timers, the callback is guarenteed to be invoked only when the
+As with timers, the callback is guaranteed to be invoked only when the
 time (C<at>) has passed, but if multiple periodic timers become ready
 during the same loop iteration then order of execution is undefined.
 =head3 Watcher-Specific Functions and Data Members
 =over 4
 =item * absolute timer (at = time, interval = reschedule_cb = 0)
-In this configuration the watcher triggers an event after the wallclock
+In this configuration the watcher triggers an event after the wall clock
 time C<at> has passed and doesn't repeat. It will not adjust when a time
 jump occurs, that is, if it is to be run at January 1st 2011 then it will
 run when the system time reaches or surpasses this time.
 =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
 the hour:
    ev_periodic_set (&periodic, 0., 3600., 0);
 This doesn't mean there will always be 3600 seconds in between triggers,
-but only that the the callback will be called when the system time shows a
+but only that the callback will be called when the system time shows a
 full hour (UTC), or more correctly, when the system time is evenly divisible
 by 3600.
 Another way to think about it (for the mathematically inclined) is that
 C<ev_periodic> will try to run the callback in this mode at the next possible
 For numerical stability it is preferable that the C<at> value is near
 C<ev_now ()> (the current time), but there is no range requirement for
 this value, and in fact is often specified as zero.
-Note also that there is an upper limit to how often a timer can fire (cpu
+Note also that there is an upper limit to how often a timer can fire (CPU
 speed for example), so if C<interval> is very small then timing stability
-will of course detoriate. Libev itself tries to be exact to be about one
+will of course deteriorate. Libev itself tries to be exact to be about one
 millisecond (if the OS supports it and the machine is fast enough).
 =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
 In this mode the values for C<interval> and C<at> are both being
 =head3 Examples
 Example: Call a callback every hour, or, more precisely, whenever the
 system clock is divisible by 3600. The callback invocation times have
-potentially a lot of jittering, but good long-term stability.
+potentially a lot of jitter, but good long-term stability.
   static void
   clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
   {
     ... its now a full hour (UTC, or TAI or whatever your clock follows)
 as you don't register any with libev). Similarly, when the last signal
 watcher for a signal is stopped libev will reset the signal handler to
 SIG_DFL (regardless of what it was set to before).
 If possible and supported, libev will install its handlers with
-C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
+C<SA_RESTART> behaviour enabled, so system calls should not be unduly
-interrupted. If you have a problem with syscalls getting interrupted by
+interrupted. If you have a problem with system calls getting interrupted by
 signals you can block all signals in an C<ev_check> watcher and unblock
 them in an C<ev_prepare> watcher.
 =head3 Watcher-Specific Functions and Data Members
 is permissible to install a child watcher I<after> the child has been
 forked (which implies it might have already exited), as long as the event
 loop isn't entered (or is continued from a watcher).
 Only the default event loop is capable of handling signals, and therefore
-you can only rgeister child watchers in the default event loop.
+you can only register child watchers in the default event loop.
 =head3 Process Interaction
 Libev grabs C<SIGCHLD> as soon as the default event loop is
 initialised. This is necessary to guarantee proper behaviour even if
-the first child watcher is started after the child exits. The occurance
+the first child watcher is started after the child exits. The occurrence
 of C<SIGCHLD> is recorded asynchronously, but child reaping is done
 synchronously as part of the event loop processing. Libev always reaps all
 children, even ones not watched.
 =head3 Overriding the Built-In Processing
     }
 =head2 C<ev_stat> - did the file attributes just change?
-This watches a filesystem path for attribute changes. That is, it calls
+This watches a file system path for attribute changes. That is, it calls
 C<stat> regularly (or when the OS says it changed) and sees if it changed
 compared to the last time, invoking the callback if it did.
 The path does not need to exist: changing from "path exists" to "path does
 not exist" is a status change like any other. The condition "path does
 disabled large file support, you get the 32 bit version of the stat
 structure. When using the library from programs that change the ABI to
 use 64 bit file offsets the programs will fail. In that case you have to
 compile libev with the same flags to get binary compatibility. This is
 obviously the case with any flags that change the ABI, but the problem is
-most noticably with ev_stat and largefile support.
+most noticeably with ev_stat and large file support.
 =head3 Inotify
 When C<inotify (7)> support has been compiled into libev (generally only
 available on Linux) and present at runtime, it will be used to speed up
 implement this functionality, due to the requirement of having a file
 descriptor open on the object at all times).
 =head3 The special problem of stat time resolution
-The C<stat ()> syscall only supports full-second resolution portably, and
+The C<stat ()> system call only supports full-second resolution portably, and
-even on systems where the resolution is higher, many filesystems still
+even on systems where the resolution is higher, many file systems still
 only support whole seconds.
 That means that, if the time is the only thing that changes, you can
 easily miss updates: on the first update, C<ev_stat> detects a change and
 calls your callback, which does something. When there is another update
 The specified interval.
 =item const char *path [read-only]
-The filesystem path that is being watched.
+The file system path that is being watched.
 =back
 =head3 Examples
 This is done by examining in each prepare call which file descriptors need
 to be watched by the other library, registering C<ev_io> watchers for
 them and starting an C<ev_timer> watcher for any timeouts (many libraries
 provide just this functionality). Then, in the check watcher you check for
-any events that occured (by checking the pending status of all watchers
+any events that occurred (by checking the pending status of all watchers
 and stopping them) and call back into the library. The I/O and timer
 callbacks will never actually be called (but must be valid nevertheless,
 because you never know, you know?).
 As another example, the Perl Coro module uses these hooks to integrate
 Method 2: This would be just like method 1, but you run C<adns_afterpoll>
 in the prepare watcher and would dispose of the check watcher.
 Method 3: If the module to be embedded supports explicit event
-notification (adns does), you can also make use of the actual watcher
+notification (libadns does), you can also make use of the actual watcher
 callbacks, and only destroy/create the watchers in the prepare watcher.
   static void
   timer_cb (EV_P_ ev_timer *w, int revents)
   {
   }
   // do not ever call adns_afterpoll
 Method 4: Do not use a prepare or check watcher because the module you
-want to embed is too inflexible to support it. Instead, youc na override
+want to embed is too inflexible to support it. Instead, you can override
 their poll function.  The drawback with this solution is that the main
 loop is now no longer controllable by EV. The C<Glib::EV> module does
 this.
   static gint
 Configures the watcher to embed the given loop, which must be
 embeddable. If the callback is C<0>, then C<ev_embed_sweep> 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,
-if you do not want thta, you need to temporarily stop the embed watcher).
+if you do not want that, you need to temporarily stop the embed watcher).
 =item ev_embed_sweep (loop, ev_embed *)
 Make a single, non-blocking sweep over the embedded loop. This works
 similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
-apropriate way for embedded loops.
+appropriate way for embedded loops.
 =item struct ev_loop *other [read-only]
 The embedded event loop.
 =head3 Examples
 Example: Try to get an embeddable event loop and embed it into the default
 event loop. If that is not possible, use the default loop. The default
-loop is stored in C<loop_hi>, while the mebeddable loop is stored in
+loop is stored in C<loop_hi>, while the embeddable loop is stored in
-C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
+C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
 used).
   struct ev_loop *loop_hi = ev_default_init (0);
   struct ev_loop *loop_lo = 0;
   struct ev_embed embed;
 =item queueing from a signal handler context
 To implement race-free queueing, you simply add to the queue in the signal
 handler but you block the signal handler in the watcher callback. Here is an example that does that for
-some fictitiuous SIGUSR1 handler:
+some fictitious SIGUSR1 handler:
    static ev_async mysig;
    static void
    sigusr1_handler (void)
 =item ev_async_send (loop, ev_async *)
 Sends/signals/activates the given C<ev_async> watcher, that is, feeds
 an C<EV_ASYNC> event on the watcher into the event loop. Unlike
 C<ev_feed_event>, this call is safe to do in other threads, signal or
-similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
+similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
 section below on what exactly this means).
-This call incurs the overhead of a syscall only once per loop iteration,
+This call incurs the overhead of a system call only once per loop iteration,
-so while the overhead might be noticable, it doesn't apply to repeated
+so while the overhead might be noticeable, it doesn't apply to repeated
 calls to C<ev_async_send>.
 =item bool = ev_async_pending (ev_async *)
 Returns a non-zero value when C<ev_async_send> has been called on the
 event loop.
 C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
 the loop iterates next and checks for the watcher to have become active,
 it will reset the flag again. C<ev_async_pending> can be used to very
-quickly check wether invoking the loop might be a good idea.
+quickly check whether invoking the loop might be a good idea.
-Not that this does I<not> check wether the watcher itself is pending, only
+Not that this does I<not> check whether the watcher itself is pending, only
-wether it has been requested to make this watcher pending.
+whether it has been requested to make this watcher pending.
 =back
 =head1 OTHER FUNCTIONS
 or timeout without having to allocate/configure/start/stop/free one or
 more watchers yourself.
 If C<fd> is less than 0, then no I/O watcher will be started and events
 is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
-C<events> set will be craeted and started.
+C<events> set will be created and started.
 If C<timeout> is less than 0, then no timeout watcher will be
 started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
 repeat = 0) will be started. While C<0> is a valid timeout, it is of
 dubious value.
 Feed an event on the given fd, as if a file descriptor backend detected
 the given events it.
 =item ev_feed_signal_event (ev_loop *loop, int signum)
-Feed an event as if the given signal occured (C<loop> must be the default
+Feed an event as if the given signal occurred (C<loop> must be the default
 loop!).
 =back
 =back
 =head1 C++ SUPPORT
 Libev comes with some simplistic wrapper classes for C++ that mainly allow
-you to use some convinience methods to start/stop watchers and also change
+you to use some convenience methods to start/stop watchers and also change
 the callback model to a model using method callbacks on objects.
 To use it,
   #include <ev++.h>
 =item w->set (struct ev_loop *)
 Associates a different C<struct ev_loop> with this watcher. You can only
 do this when the watcher is inactive (and not pending either).
-=item w->set ([args])
+=item w->set ([arguments])
-Basically the same as C<ev_TYPE_set>, with the same args. Must be
+Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
 called at least once. Unlike the C counterpart, an active watcher gets
 automatically stopped and restarted when reconfiguring it with this
 method.
 =item w->start ()
 =head1 OTHER LANGUAGE BINDINGS
 Libev does not offer other language bindings itself, but bindings for a
-numbe rof languages exist in the form of third-party packages. If you know
+number of languages exist in the form of third-party packages. If you know
 any interesting language binding in addition to the ones listed here, drop
 me a note.
 =over 4
 L<http://software.schmorp.de/pkg/EV>.
 =item Ruby
 Tony Arcieri has written a ruby extension that offers access to a subset
-of the libev API and adds filehandle abstractions, asynchronous DNS and
+of the libev API and adds file handle abstractions, asynchronous DNS and
 more on top of it. It can be found via gem servers. Its homepage is at
 L<http://rev.rubyforge.org/>.
 =item D
 =back
 =head1 MACRO MAGIC
-Libev can be compiled with a variety of options, the most fundamantal
+Libev can be compiled with a variety of options, the most fundamental
 of which is C<EV_MULTIPLICITY>. This option determines whether (most)
 functions and callbacks have an initial C<struct ev_loop *> argument.
 To make it easier to write programs that cope with either variant, the
 following macros are defined:
 libev somewhere in your source tree).
 =head2 FILESETS
 Depending on what features you need you need to include one or more sets of files
-in your app.
+in your application.
 =head3 CORE EVENT LOOP
 To include only the libev core (all the C<ev_*> functions), with manual
 configuration (no autoconf):
   event.h
   event.c
 =head3 AUTOCONF SUPPORT
-Instead of using C<EV_STANDALONE=1> and providing your config in
+Instead of using C<EV_STANDALONE=1> and providing your configuration in
 whatever way you want, you can also C<m4_include([libev.m4])> in your
 F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
 include F<config.h> and configure itself accordingly.
 For this of course you need the m4 file:
   libev.m4
 =head2 PREPROCESSOR SYMBOLS/MACROS
 Libev can be configured via a variety of preprocessor symbols you have to
-define before including any of its files. The default in the absense of
+define before including any of its files. The default in the absence of
 autoconf is noted for every option.
 =over 4
 =item EV_STANDALONE
 F<event.h> that are not directly supported by the libev core alone.
 =item EV_USE_MONOTONIC
 If defined to be C<1>, libev will try to detect the availability of the
-monotonic clock option at both compiletime and runtime. Otherwise no use
+monotonic clock option at both compile time and runtime. Otherwise no use
 of the monotonic clock option will be attempted. If you enable this, you
 usually have to link against librt or something similar. Enabling it when
 the functionality isn't available is safe, though, although you have
 to make sure you link against any libraries where the C<clock_gettime>
 function is hiding in (often F<-lrt>).
 =item EV_USE_REALTIME
 If defined to be C<1>, libev will try to detect the availability of the
-realtime clock option at compiletime (and assume its availability at
+real-time clock option at compile time (and assume its availability at
-runtime if successful). Otherwise no use of the realtime clock option will
+runtime if successful). Otherwise no use of the real-time clock option will
 be attempted. This effectively replaces C<gettimeofday> by C<clock_get
 (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
 note about libraries in the description of C<EV_USE_MONOTONIC>, though.
 =item EV_USE_NANOSLEEP
 2.7 or newer, otherwise disabled.
 =item EV_USE_SELECT
 If undefined or defined to be C<1>, libev will compile in support for the
-C<select>(2) backend. No attempt at autodetection will be done: if no
+C<select>(2) backend. No attempt at auto-detection will be done: if no
 other method takes over, select will be it. Otherwise the select backend
 will not be compiled in.
 =item EV_SELECT_USE_FD_SET
 If defined to C<1>, then the select backend will use the system C<fd_set>
 structure. This is useful if libev doesn't compile due to a missing
-C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
+C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
 exotic systems. This usually limits the range of file descriptors to some
 low limit such as 1024 or might have other limitations (winsocket only
 allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
 influence the size of the C<fd_set> used.
 otherwise another method will be used as fallback. This is the preferred
 backend for Solaris 10 systems.
 =item EV_USE_DEVPOLL
-reserved for future expansion, works like the USE symbols above.
+Reserved for future expansion, works like the USE symbols above.
 =item EV_USE_INOTIFY
 If defined to be C<1>, libev will compile in support for the Linux inotify
 interface to speed up C<ev_stat> watchers. Its actual availability will
 access is atomic with respect to other threads or signal contexts. No such
 type is easily found in the C language, so you can provide your own type
 that you know is safe for your purposes. It is used both for signal handler "locking"
 as well as for signal and thread safety in C<ev_async> watchers.
-In the absense of this define, libev will use C<sig_atomic_t volatile>
+In the absence of this define, libev will use C<sig_atomic_t volatile>
 (from F<signal.h>), which is usually good enough on most platforms.
 =item EV_H
 The name of the F<ev.h> header file used to include it. The default if
 When doing priority-based operations, libev usually has to linearly search
 all the priorities, so having many of them (hundreds) uses a lot of space
 and time, so using the defaults of five priorities (-2 .. +2) is usually
 fine.
-If your embedding app does not need any priorities, defining these both to
+If your embedding application does not need any priorities, defining these both to
-C<0> will save some memory and cpu.
+C<0> will save some memory and CPU.
 =item EV_PERIODIC_ENABLE
 If undefined or defined to be C<1>, then periodic timers are supported. If
 defined to be C<0>, then they are not. Disabling them saves a few kB of
 =item EV_MINIMAL
 If you need to shave off some kilobytes of code at the expense of some
 speed, define this symbol to C<1>. Currently this is used to override some
-inlining decisions, saves roughly 30% codesize of amd64. It also selects a
+inlining decisions, saves roughly 30% code size on amd64. It also selects a
 much smaller 2-heap for timer management over the default 4-heap.
 =item EV_PID_HASHSIZE
 C<ev_child> watchers use a small hash table to distribute workload by
 =item EV_USE_4HEAP
 Heaps are not very cache-efficient. To improve the cache-efficiency of the
 timer and periodics heap, libev uses a 4-heap when this symbol is defined
 to C<1>. The 4-heap uses more complicated (longer) code but has
-noticably faster performance with many (thousands) of watchers.
+noticeably faster performance with many (thousands) of watchers.
 The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
 (disabled).
 =item EV_HEAP_CACHE_AT
 Heaps are not very cache-efficient. To improve the cache-efficiency of the
 timer and periodics heap, libev can cache the timestamp (I<at>) within
 the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
 which uses 8-12 bytes more per watcher and a few hundred bytes more code,
 but avoids random read accesses on heap changes. This improves performance
-noticably with with many (hundreds) of watchers.
+noticeably with with many (hundreds) of watchers.
 The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
 (disabled).
 =item EV_VERIFY
 avoid the C<struct ev_loop *> as first argument in all cases, or to use
 method calls instead of plain function calls in C++.
 =head2 EXPORTED API SYMBOLS
-If you need to re-export the API (e.g. via a dll) and you need a list of
+If you need to re-export the API (e.g. via a DLL) and you need a list of
 exported symbols, you can use the provided F<Symbol.*> files which list
 all public symbols, one per line:
   Symbols.ev      for libev proper
   Symbols.event   for the libevent emulation
 This can also be used to rename all public symbols to avoid clashes with
 multiple versions of libev linked together (which is obviously bad in
-itself, but sometimes it is inconvinient to avoid this).
+itself, but sometimes it is inconvenient to avoid this).
 A sed command like this will create wrapper C<#define>'s that you need to
 include before including F<ev.h>:
    <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
 =head1 THREADS AND COROUTINES
 =head2 THREADS
-Libev itself is completely threadsafe, but it uses no locking. This
+Libev itself is completely thread-safe, but it uses no locking. This
 means that you can use as many loops as you want in parallel, as long as
 only one thread ever calls into one libev function with the same loop
 parameter.
 Or put differently: calls with different loop parameters can be done in
 help you but by giving some generic advice:
 =over 4
 =item * most applications have a main thread: use the default libev loop
-in that thread, or create a seperate thread running only the default loop.
+in that thread, or create a separate thread running only the default loop.
 This helps integrating other libraries or software modules that use libev
 themselves and don't care/know about threading.
 =item * one loop per thread is usually a good model.
 Doing this is almost never wrong, sometimes a better-performance model
 exists, but it is always a good start.
 =item * other models exist, such as the leader/follower pattern, where one
-loop is handed through multiple threads in a kind of round-robbin fashion.
+loop is handed through multiple threads in a kind of round-robin fashion.
-Chosing a model is hard - look around, learn, know that usually you cna do
+Choosing a model is hard - look around, learn, know that usually you can do
 better than you currently do :-)
 =item * often you need to talk to some other thread which blocks in the
 event loop - C<ev_async> watchers can be used to wake them up from other
 threads safely (or from signal contexts...).
 =back
 =head2 COROUTINES
-Libev is much more accomodating to coroutines ("cooperative threads"):
+Libev is much more accommodating to coroutines ("cooperative threads"):
 libev fully supports nesting calls to it's functions from different
 coroutines (e.g. you can call C<ev_loop> on the same loop from two
 different coroutines and switch freely between both coroutines running the
 loop, as long as you don't confuse yourself). The only exception is that
 you must not do this from C<ev_periodic> reschedule callbacks.
 =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
 A change means an I/O watcher gets started or stopped, which requires
 libev to recalculate its status (and possibly tell the kernel, depending
-on backend and wether C<ev_io_set> was used).
+on backend and whether C<ev_io_set> was used).
 =item Activating one watcher (putting it into the pending state): O(1)
 =item Priority handling: O(number_of_priorities)
 =item Processing ev_async_send: O(number_of_async_watchers)
 =item Processing signals: O(max_signal_number)
-Sending involves a syscall I<iff> there were no other C<ev_async_send>
+Sending involves a system call I<iff> there were no other C<ev_async_send>
 calls in the current loop iteration. Checking for async and signal events
 involves iterating over all running async watchers or all signal numbers.
 =back
 the abysmal performance of winsockets, using a large number of sockets
 is not recommended (and not reasonable). If your program needs to use
 more than a hundred or so sockets, then likely it needs to use a totally
 different implementation for windows, as libev offers the POSIX readiness
 notification model, which cannot be implemented efficiently on windows
-(microsoft monopoly games).
+(Microsoft monopoly games).
 =over 4
 =item The winsocket select function
-The winsocket C<select> function doesn't follow POSIX in that it requires
+The winsocket C<select> function doesn't follow POSIX in that it
-socket I<handles> and not socket I<file descriptors>. This makes select
+requires socket I<handles> and not socket I<file descriptors> (it is
-very inefficient, and also requires a mapping from file descriptors
+also extremely buggy). This makes select very inefficient, and also
-to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
+requires a mapping from file descriptors to socket handles. See the
-C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
+discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
-symbols for more info.
+C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
-The configuration for a "naked" win32 using the microsoft runtime
+The configuration for a "naked" win32 using the Microsoft runtime
 libraries and raw winsocket select is:
   #define EV_USE_SELECT 1
   #define EV_SELECT_IS_WINSOCKET 1   /* forces EV_SELECT_USE_FD_SET, too */
 Windows has numerous arbitrary (and low) limits on things.
 Early versions of winsocket's select only supported waiting for a maximum
 of C<64> handles (probably owning to the fact that all windows kernels
-can only wait for C<64> things at the same time internally; microsoft
+can only wait for C<64> things at the same time internally; Microsoft
 recommends spawning a chain of threads and wait for 63 handles and the
 previous thread in each. Great).
 Newer versions support more handles, but you need to define C<FD_SETSIZE>
 to some high number (e.g. C<2048>) before compiling the winsocket select
 call (which might be in libev or elsewhere, for example, perl does its own
 select emulation on windows).
-Another limit is the number of file descriptors in the microsoft runtime
+Another limit is the number of file descriptors in the Microsoft runtime
 libraries, which by default is C<64> (there must be a hidden I<64> fetish
-or something like this inside microsoft). You can increase this by calling
+or something like this inside Microsoft). You can increase this by calling
 C<_setmaxstdio>, which can increase this limit to C<2048> (another
-arbitrary limit), but is broken in many versions of the microsoft runtime
+arbitrary limit), but is broken in many versions of the Microsoft runtime
 libraries.
 This might get you to about C<512> or C<2048> sockets (depending on
 windows version and/or the phase of the moon). To get more, you need to
 wrap all I/O functions and provide your own fd management, but the cost of
 =back
 If you know of other additional requirements drop me a note.
+=head1 COMPILER WARNINGS
+Depending on your compiler and compiler settings, you might get no or a
+lot of warnings when compiling libev code. Some people are apparently
+scared by this.
+However, these are unavoidable for many reasons. For one, each compiler
+has different warnings, and each user has different tastes regarding
+warning options. "Warn-free" code therefore cannot be a goal except when
+targeting a specific compiler and compiler-version.
+Another reason is that some compiler warnings require elaborate
+workarounds, or other changes to the code that make it less clear and less
+maintainable.
+And of course, some compiler warnings are just plain stupid, or simply
+wrong (because they don't actually warn about the condition their message
+seems to warn about).
+While libev is written to generate as few warnings as possible,
+"warn-free" code is not a goal, and it is recommended not to build libev
+with any compiler warnings enabled unless you are prepared to cope with
+them (e.g. by ignoring them). Remember that warnings are just that:
+warnings, not errors, or proof of bugs.
 =head1 VALGRIND
 Valgrind has a special section here because it is a popular tool that is
 highly useful, but valgrind reports are very hard to interpret.
    ==2274==    definitely lost: 0 bytes in 0 blocks.
    ==2274==      possibly lost: 0 bytes in 0 blocks.
    ==2274==    still reachable: 256 bytes in 1 blocks.
-then there is no memory leak. Similarly, under some circumstances,
+Then there is no memory leak. Similarly, under some circumstances,
 valgrind might report kernel bugs as if it were a bug in libev, or it
 might be confused (it is a very good tool, but only a tool).
 If you are unsure about something, feel free to contact the mailing list
 with the full valgrind report and an explanation on why you think this is

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Comparing libev/ev.pod (file contents): Revision 1.159 by root, Thu May 22 02:44:57 2008 UTC vs. Revision 1.161 by root, Sat May 24 03:08:03 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.159 by root, Thu May 22 02:44:57 2008 UTC vs.
Revision 1.161 by root, Sat May 24 03:08:03 2008 UTC