+Revision history for libev, a high-performance and full-featured event loop.
+TODO: EV_STANDALONE == NO_HASSEL (do not use clock_gettime in ev_standalone)
+TODO: faq, process a thing in each iteration
+TODO: dbeugging tips, ev_verify, ev_init twice
+TODO: ev_break for immediate exit (EVBREAK_NOW?)
+TODO: document the special problem of signals around fork.
+TODO: store pid for each signal
+TODO: document file descriptor usage per loop
+TODO: store loop pid_t and compare isndie signal handler,store 1 for same, 2 for differign pid, clean up in loop_fork
+TODO: embed watchers need updating when fd changes
+TODO: document portbaility requirements for atomic pointer access
+ - destroying a non-default loop would stop the global waitpid
+ watcher (Denis Bilenko).
+ - queueing pending watchers of higher priority from a watcher now invokes
+ them in a timely fashion (reported by Denis Bilenko).
+ - add throw() to all libev functions that cannot throw exceptions, for
+ further code size decrease when compiling for C++.
+ - add throw () to callbacks that must not throw exceptions (allocator,
+ syserr, loop acquire/release, periodic reschedule cbs).
+ - fix event_base_loop return code, add event_get_callback, event_base_new,
+ event_base_get_method calls to improve libevent 1.x emulation and add
+ some libevent 2.x functionality (based on a patch by Jeff Davey).
+ - add more memory fences to fix a bug reported by Jeff Davey. Better
+ be overfenced than underprotected.
+ - ev_run now returns a boolean status (true meaning watchers are
+ - ev_once: undef EV_ERROR in ev_kqueue.c, to avoid clashing with
+ libev's EV_ERROR (reported by 191919).
+ - (ecb) add memory fence support for xlC (Darin McBride).
+ - (ecb) add memory fence support for gcc-mips (Anton Kirilov).
+ - (ecb) add memory fence support for gcc-alpha (Christian Weisgerber).
+ - work around some kernels losing file descriptors by leaking
+ the kqueue descriptor in the child.
+ - include sys/syscall.h instead of plain syscall.h.
+ - check for io watcher loops in ev_verify, check for the most
+ common reported usage bug in ev_io_start.
+ - chose socket vs. WSASocket at compiletime using EV_USE_WSASOCKET.
+ - always use WSASend/WSARecv directly on windows, hoping that this
+ works in all cases (unlike read/write/send/recv...).
+ - try to detect signals around a fork faster (test program by
+ - work around recent glibc versions that leak memory in realloc.
+ - rename ev::embed::set to ev::embed::set_embed to avoid clashing
+ the watcher base set (loop) method.
+ - rewrite the async/signal pipe logic to always keep a valid fd, which
+ simplifies (and hopefuly correctifies :) the race checking
+ on fork, at the cost of one extra fd.
+4.11 Sat Feb 4 19:52:39 CET 2012
+ - INCOMPATIBLE CHANGE: ev_timer_again now clears the pending status, as
+ was documented already, but not implemented in the repeating case.
+ - new compiletime symbols: EV_NO_SMP and EV_NO_THREADS.
+ - fix a race where the workaround against the epoll fork bugs
+ caused signals to not be handled anymore.
+ - correct backend_fudge for most backends, and implement a windows
+ specific workaround to avoid looping because we call both
+ select and Sleep, both with different time resolutions.
+ - document range and guarantees of ev_sleep.
+ - document reasonable ranges for periodics interval and offset.
+ - rename backend_fudge to backend_mintime to avoid future confusion :)
+ - change the default periodic reschedule function to hopefully be more
+ exact and correct even in corner cases or in the far future.
+ - do not rely on -lm anymore: use it when available but use our
+ own floor () if it is missing. This should make it easier to embed,
+ as no external libraries are required.
+ - strategically import macros from libecb and mark rarely-used functions
+ as cache-cold (saving almost 2k code size on typical amd64 setups).
+ - add Symbols.ev and Symbols.event files, that were missing.
+ - fix backend_mintime value for epoll (was 1/1024, is 1/1000 now).
+ - fix #3 "be smart about timeouts" to not "deadlock" when
+ timeout == now, also improve the section overall.
+ - avoid "AVOIDING FINISHING BEFORE RETURNING" idiom.
+ - support new EV_API_STATIC mode to make all libev symbols
+ - supply default CFLAGS of -g -O3 with gcc when original CFLAGS
+4.04 Wed Feb 16 09:01:51 CET 2011
+ - fix two problems in the native win32 backend, where reuse of fd's
+ with different underlying handles caused handles not to be removed
+ or added to the select set (analyzed and tested by Bert Belder).
+ - do no rely on ceil() in ev_e?poll.c.
+ - backport libev to HP-UX versions before 11 v3.
+ - configure did not detect nanosleep and clock_gettime properly when
+ they are available in the libc (as opposed to -lrt).
+4.03 Tue Jan 11 14:37:25 CET 2011
+ - officially support polling files with all backends.
+ - support files, /dev/zero etc. the same way as select in the epoll
+ backend, by generating events on our own.
+ - ports backend: work around solaris bug 6874410 and many related ones
+ (EINTR, maybe more), with no performance loss (note that the solaris
+ bug report is actually wrong, reality is far more bizarre and broken
+ - define EV_READ/EV_WRITE as macros in event.h, as some programs use
+ #ifdef to test for them.
+ - new (experimental) function: ev_feed_signal.
+ - new (to become default) EVFLAG_NOSIGMASK flag.
+ - new EVBACKEND_MASK symbol.
+ - updated COMMON IDIOMS SECTION.
+4.01 Fri Nov 5 21:51:29 CET 2010
+ - automake fucked it up, apparently, --add-missing -f is not quite enough
+ to make it update its files, so 4.00 didn't install ev++.h and
+ event.h on make install. grrr.
+ - ev_loop(count|depth) didn't return anything (Robin Haberkorn).
+ - change EV_UNDEF to 0xffffffff to silence some overzealous compilers.
+ - use "(libev) " prefix for all libev error messages now.
+4.00 Mon Oct 25 12:32:12 CEST 2010
+ - "PORTING FROM LIBEV 3.X TO 4.X" (in ev.pod) is recommended reading.
+ - ev_embed_stop did not correctly stop the watcher (very good
+ testcase by Vladimir Timofeev).
+ - ev_run will now always update the current loop time - it erroneously
+ didn't when idle watchers were active, causing timers not to fire.
+ - fix a bug where a timeout of zero caused the timer not to fire
+ in the libevent emulation (testcase by Péter Szabó).
+ - applied win32 fixes by Michael Lenaghan (also James Mansion).
+ - replace EV_MINIMAL by EV_FEATURES.
+ - prefer EPOLL_CTL_ADD over EPOLL_CTL_MOD in some more cases, as it
+ seems the former is *much* faster than the latter.
+ - linux kernel version detection (for inotify bug workarounds)
+ - reduce the number of spurious wake-ups with the ports backend.
+ - remove dependency on sys/queue.h on freebsd (patch by Vanilla Hsu).
+ - do async init within ev_async_start, not ev_async_set, which avoids
+ an API quirk where the set function must be called in the C++ API
+ even when there is nothing to set.
+ - add (undocumented) EV_ENABLE when adding events with kqueue,
+ this might help with OS X, which seems to need it despite documenting
+ not to need it (helpfully pointed out by Tilghman Lesher).
+ - do not use poll by default on freebsd, it's broken (what isn't
+ - allow to embed epoll on kernels >= 2.6.32.
+ - configure now prepends -O3, not appends it, so one can still
+ - ev.pod: greatly expanded the portability section, added a porting
+ section, a description of watcher states and made lots of minor fixes.
+ - disable poll backend on AIX, the poll header spams the namespace
+ and it's not worth working around dead platforms (reported
+ and analyzed by Aivars Kalvans).
+ - improve header file compatibility of the standalone eventfd code
+ - implement EV_AVOID_STDIO option.
+ - do not use sscanf to parse linux version number (smaller, faster,
+ - new EV_CHILD_ENABLE and EV_SIGNAL_ENABLE configurable settings.
+ - update libev.m4 HAVE_CLOCK_SYSCALL test for newer glibcs.
+ - add section on accept() problems to the manpage.
+ - rename EV_TIMEOUT to EV_TIMER.
+ - rename ev_loop_count/depth/verify/loop/unloop.
+ - remove ev_default_destroy and ev_default_fork.
+ - switch to two-digit minor version.
+ - work around an apparent gentoo compiler bug.
+ - define _DARWIN_UNLIMITED_SELECT. just so.
+ - use enum instead of #define for most constants.
+ - improve compatibility to older C++ compilers.
+ - (experimental) ev_run/ev_default_loop/ev_break/ev_loop_new have now
+ default arguments when compiled as C++.
+ - enable automake dependency tracking.
+ - ev_loop_new no longer leaks memory when loop creation failed.
+ - new ev_cleanup watcher type.
+3.9 Thu Dec 31 07:59:59 CET 2009
+ - signalfd is no longer used by default and has to be requested
+ explicitly - this means that easy to catch bugs become hard to
+ catch race conditions, but the users have spoken.
+ - point out the unspecified signal mask in the documentation, and
+ that this is a race condition regardless of EV_SIGNALFD.
+ - backport inotify code to C89.
+ - inotify file descriptors could leak into child processes.
+ - ev_stat watchers could keep an erroneous extra ref on the loop,
+ preventing exit when unregistering all watchers (testcases
+ provided by email@example.com).
+ - implement EV_WIN32_HANDLE_TO_FD and EV_WIN32_CLOSE_FD configuration
+ symbols to make it easier for apps to do their own fd management.
+ - support EV_IDLE_ENABLE being disabled in ev++.h
+ (patch by Didier Spezia).
+ - take advantage of inotify_init1, if available, to set cloexec/nonblock
+ on fd creation, to avoid races.
+ - the signal handling pipe wasn't always initialised under windows
+ - changed minimum glibc requirement from glibc 2.9 to 2.7, for
+ - add missing string.h include (Denis F. Latypoff).
+ - only replace ev_stat.prev when we detect an actual difference,
+ so prev is (almost) always different to attr. this might
+ have caused the problems with 04_stat.t.
+ - add ev::timer->remaining () method to C++ API.
+3.8 Sun Aug 9 14:30:45 CEST 2009
+ - incompatible change: do not necessarily reset signal handler
+ to SIG_DFL when a sighandler is stopped.
+ - ev_default_destroy did not properly free or zero some members,
+ potentially causing crashes and memory corruption on repeated
+ ev_default_destroy/ev_default_loop calls.
+ - take advantage of signalfd on GNU/Linux systems.
+ - document that the signal mask might be in an unspecified
+ state when using libev's signal handling.
+ - take advantage of some GNU/Linux calls to set cloexec/nonblock
+ on fd creation, to avoid race conditions.
+3.7 Fri Jul 17 16:36:32 CEST 2009
+ - ev_unloop and ev_loop wrongly used a global variable to exit loops,
+ instead of using a per-loop variable (bug caught by accident...).
+ - the ev_set_io_collect_interval interpretation has changed.
+ - add new functionality: ev_set_userdata, ev_userdata,
+ ev_set_invoke_pending_cb, ev_set_loop_release_cb,
+ ev_invoke_pending, ev_pending_count, together with a long example
+ - add ev_timer_remaining (as requested by Denis F. Latypoff).
+ - calling ev_unloop in fork/prepare watchers will no longer poll
+ - Denis F. Latypoff corrected many typos in example code snippets.
+ - honor autoconf detection of EV_USE_CLOCK_SYSCALL, also double-
+ check that the syscall number is available before trying to
+ use it (reported by ry@tinyclouds).
+ - use GetSystemTimeAsFileTime instead of _timeb on windows, for
+ slightly higher accuracy.
+ - properly declare ev_loop_verify and ev_now_update even when
+ - do not compile in any priority code when EV_MAXPRI == EV_MINPRI.
+ - support EV_MINIMAL==2 for a reduced API.
+ - actually 0-initialise struct sigaction when installing signals.
+ - add section on hibernate and stopped processes to ev_timer docs.
+3.6 Tue Apr 28 02:49:30 CEST 2009
+ - multiple timers becoming ready within an event loop iteration
+ will be invoked in the "correct" order now.
+ - do not leave the event loop early just because we have no active
+ watchers, fixing a problem when embedding a kqueue loop
+ that has active kernel events but no registered watchers
+ (reported by blacksand blacksand).
+ - correctly zero the idx values for arrays, so destroying and
+ reinitialising the default loop actually works (patch by
+ - implement ev_suspend and ev_resume.
+ - new EV_CUSTOM revents flag for use by applications.
+ - add documentation section about priorities.
+ - add a glossary to the dcoumentation.
+ - extend the ev_fork description slightly.
+ - optimize a jump out of call_pending.
+3.53 Sun Feb 15 02:38:20 CET 2009
+ - fix a bug in event pipe creation on win32 that would cause a
+ failed assertion on event loop creation (patch by Malek Hadj-Ali).
+ - probe for CLOCK_REALTIME support at runtime as well and fall
+ back to gettimeofday if there is an error, to support older
+ operating systems with newer header files/libraries.
+ - prefer gettimeofday over clock_gettime with USE_CLOCK_SYSCALL
+ (default most everywhere), otherwise not.
+3.52 Wed Jan 7 21:43:02 CET 2009
+ - fix compilation of select backend in fd_set mode when NFDBITS is
+ missing (to get it to compile on QNX, reported by Rodrigo Campos).
+ - better select-nfds handling when select backend is in fd_set mode.
+ - diagnose fd_set overruns when select backend is in fd_set mode.
+ - due to a thinko, instead of disabling everything but
+ select on the borked OS X platform, everything but select was
+ allowed (reported by Emanuele Giaquinta).
+ - actually verify that local and remote port are matching in
+ libev's socketpair emulation, which makes denial-of-service
+ attacks harder (but not impossible - it's windows). Make sure
+ it even works under vista, which thinks that getpeer/sockname
+ should return fantasy port numbers.
+ - include "libev" in all assertion messages for potentially
+ - event_get_version (libevent compatibility) returned
+ a useless string instead of the expected version string
+ (patch by W.C.A. Wijngaards).
+3.51 Wed Dec 24 23:00:11 CET 2008
+ - fix a bug where an inotify watcher was added twice, causing
+ freezes on hash collisions (reported and analysed by Graham Leggett).
+ - new config symbol, EV_USE_CLOCK_SYSCALL, to make libev use
+ a direct syscall - slower, but no dependency on librt et al.
+ - assume negative return values != -1 signals success of port_getn
+ (no known failure reports, but it doesn't hurt).
+ - fork detection in ev_embed now stops and restarts the watcher
+ - EXPERIMENTAL: default the method to operator () in ev++.h,
+ to make it nicer to use functors (requested by Benedek László).
+ - fixed const object callbacks in ev++.h.
+ - replaced loop_ref argument of watcher.set (loop) by a direct
+ ev_loop * in ev++.h, to avoid clashes with functor patch.
+ - do not try to watch the empty string via inotify.
+ - inotify watchers could be leaked under certain circumstances.
+ - OS X 10.5 is actually even more broken than earlier versions,
+ so fall back to select on that piece of garbage.
+ - fixed some weirdness in the ev_embed documentation.
+3.49 Wed Nov 19 11:26:53 CET 2008
+ - ev_stat watchers will now use inotify as a mere hint on
+ kernels <2.6.25, or if the filesystem is not in the
+ "known to be good" list.
+ - better mingw32 compatibility (it's not as borked as native win32)
+ (analysed by Roger Pack).
+ - include stdio.h in the example program, as too many people are
+ confused by the weird C language otherwise. I guess the next thing
+ I get told is that the "..." ellipses in the examples don't compile
+3.48 Thu Oct 30 09:02:37 CET 2008
+ - further optimise away the EPOLL_CTL_ADD/MOD combo in the epoll
+ backend by assuming the kernel event mask hasn't changed if
+ - work around spurious event notification bugs in epoll by using
+ a 32-bit generation counter. recreate kernel state if we receive
+ spurious notifications or unwanted events. this is very costly,
+ but I didn't come up with this horrible design.
+ - use memset to initialise most arrays now and do away with the
+ - expand time-out strategies into a "Be smart about timeouts" section.
+ - drop the "struct" from all ev_watcher declarations in the
+ documentation and did other clarifications (yeah, it was a mistake
+ to have a struct AND a function called ev_loop).
+ - fix a bug where ev_default would not initialise the default
+ loop again after it was destroyed with ev_default_destroy.
+ - rename syserr to ev_syserr to avoid name clashes when embedding,
+ do similar changes for event.c.
+3.45 Tue Oct 21 21:59:26 CEST 2008
+ - disable inotify usage on linux <2.6.25, as it is broken
+ (reported by Yoann Vandoorselaere).
+ - ev_stat erroneously would try to add inotify watchers
+ even when inotify wasn't available (this should only
+ have a performance impact).
+ - ev_once now passes both timeout and io to the callback if both
+ occur concurrently, instead of giving timeouts precedence.
+ - disable EV_USE_INOTIFY when sys/inotify.h is too old.
+3.44 Mon Sep 29 05:18:39 CEST 2008
+ - embed watchers now automatically invoke ev_loop_fork on the
+ embedded loop when the parent loop forks.
+ - new function: ev_now_update (loop).
+ - verify_watcher was not marked static.
+ - improve the "associating..." manpage section.
+ - documentation tweaks here and there.
+3.43 Sun Jul 6 05:34:41 CEST 2008
+ - include more include files on windows to get struct _stati64
+ (reported by Chris Hulbert, but doesn't quite fix his issue).
+ - add missing #include <io.h> in ev.c on windows (reported by
+3.42 Tue Jun 17 12:12:07 CEST 2008
+ - work around yet another windows bug: FD_SET actually adds fd's
+ multiple times to the fd_*SET*, despite official MSN docs claiming
+ otherwise. Reported and well-analysed by Matt Tolton.
+ - define NFDBITS to 0 when EV_SELECT_IS_WINSOCKET to make it compile
+ (reported any analysed by Chris Hulbert).
+ - fix a bug in ev_ebadf (this function is only used to catch
+ programming errors in the libev user). reported by Matt Tolton.
+ - fix a bug in fd_intern on win32 (could lead to compile errors
+ under some circumstances, but would work correctly if it compiles).
+ reported by Matt Tolton.
+ - (try to) work around missing lstat on windows.
+ - pass in the write fd set as except fd set under windows. windows
+ is so uncontrollably lame that it requires this. this means that
+ switching off oobinline is not supported (but tcp/ip doesn't
+ have oob, so that would be stupid anyways.
+ - use posix module symbol to auto-detect monotonic clock presence
+ and some other default values.
+3.41 Fri May 23 18:42:54 CEST 2008
+ - work around an obscure bug in winsocket select: if you
+ provide only empty fd sets then select returns WSAEINVAL. how sucky.
+ - improve timer scheduling stability and reduce use of time_epsilon.
+ - use 1-based 2-heap for EV_MINIMAL, simplifies code, reduces
+ codesize and makes for better cache-efficiency.
+ - use 3-based 4-heap for !EV_MINIMAL. this makes better use
+ of cpu cache lines and gives better growth behaviour than
+ - cache timestamp within heap for !EV_MINIMAL, to avoid random
+ - document/add EV_USE_4HEAP and EV_HEAP_CACHE_AT.
+ - fix a potential aliasing issue in ev_timer_again.
+ - add/document ev_periodic_at, retract direct access to ->at.
+ - improve ev_stat docs.
+ - add portability requirements section.
+ - fix manpage headers etc.
+ - normalise WSA error codes to lower range on windows.
+ - add consistency check code that can be called automatically
+ or on demand to check for internal structures (ev_loop_verify).
+3.31 Wed Apr 16 20:45:04 CEST 2008
+ - added last minute fix for ev_poll.c by Brandon Black.
+3.3 Wed Apr 16 19:04:10 CEST 2008
+ - event_base_loopexit should return 0 on success
+ - added linux eventfd support.
+ - try to autodetect epoll and inotify support
+ by libc header version if not using autoconf.
+ - new symbols: EV_DEFAULT_UC and EV_DEFAULT_UC_.
+ - declare functions defined in ev.h as inline if
+ C99 or gcc are available.
+ - enable inlining with gcc versions 2 and 3.
+ - work around broken poll implementations potentially
+ not clearing revents field in ev_poll (Brandon Black)
+ (no such systems are known at this time).
+ - work around a bug in realloc on openbsd and darwin,
+ also makes the erroneous valgrind complaints
+ go away (noted by various people).
+ - fix ev_async_pending, add c++ wrapper for ev_async
+ (based on patch sent by Johannes Deisenhofer).
+ - add sensible set method to ev::embed.
+ - made integer constants type int in ev.h.
+3.2 Wed Apr 2 17:11:19 CEST 2008
+ - fix a 64 bit overflow issue in the select backend,
+ by using fd_mask instead of int for the mask.
+ - rename internal sighandler to avoid clash with very old perls.
+ - entering ev_loop will not clear the ONESHOT or NONBLOCKING
+ flags of any outer loops anymore.
+ - add ev_async_pending.
+3.1 Thu Mar 13 13:45:22 CET 2008
+ - implement ev_async watchers.
+ - only initialise signal pipe on demand.
+ - make use of sig_atomic_t configurable.
+ - improved documentation.
+3.0 Mon Jan 28 13:14:47 CET 2008
+ - API/ABI bump to version 3.0.
+ - ev++.h includes "ev.h" by default now, not <ev.h>.
+ - slightly improved documentation.
+ - speed up signal detection after a fork.
+ - only optionally return trace status changed in ev_child
+ - experimental (and undocumented) loop wrappers for ev++.h.
+2.01 Tue Dec 25 08:04:41 CET 2007
+ - separate Changes file.
+ - fix ev_path_set => ev_stat_set typo.
+ - remove event_compat.h from the libev tarball.
+ - change how include files are found.
+ - update licenses, explicitly allow for GPL relicensing.
+2.0 Sat Dec 22 17:47:03 CET 2007
+ - new ev_sleep, ev_set_(io|timeout)_collect_interval.
+ - removed epoll from embeddable fd set.
+ - renamed ev_embed.loop to other.
+ - added exported Symbol tables.
+ - undefine member wrapper macros at the end of ev.c.
+ - respect EV_H in ev++.h.
+1.86 Tue Dec 18 02:36:57 CET 2007
+ - fix memleak on loop destroy (not relevant for perl).
+1.85 Fri Dec 14 20:32:40 CET 2007
+ - fix some aliasing issues w.r.t. timers and periodics
+ (not relevant for perl).
+(for historic versions refer to EV/Changes, found in the Perl interface)
+0.1 Wed Oct 31 21:31:48 CET 2007
+ - original version; hacked together in <24h.