The epoll interface ordinarily gives us one-millisecond
precision, so on Linux it makes perfect sense to use the
CLOCK_MONOTONIC_COARSE timer. But when the user has set the new
PRECISE_TIMER flag for an event_base (either by the
EVENT_BASE_FLAG_PRECISE_TIMER flag, or by the EVENT_PRECISE_TIMER
environment variable), they presumably want finer granularity.
On not-too-old Linuxes, we can achieve this using the Timerfd
mechanism, which accepts nanosecond granularity and understands
posix clocks. It's a little more expensive than just calling
epoll_wait(), so we won't do it by default.
When clang 2.9 was around we hoped they'd introduce support for the
normalized=id and override-init warnings by 3.0, but they haven't. We
should only add the version detection back in when clang actually
supports those warnings.
A listening socket can be enabled with the sockopt
TCP_DEFER_ACCEPT. This informs the kernel to not call the user-land
accept() until real data has been written to the socket.
A new flag LEV_OPT_DEFERRED_ACCEPT has been introduced to
automatically set this option. Optionally
evutil_make_tcp_listen_socket_deferred() can be called manually.
(Tweaked slightly by nickm.)
Linux provides some features that allow avoiding extra calls to
fcntl when creating new nonblocking/close-on-exec sockets, so
we can add wrapper functions to emulate those when they are not
available.
Additionally, even when we are emulating those functions, we can
take a fast path that cuts our fcntl calls in half: we don't need to
look up the previous value of a file's flags when we have just
created it.
Some hosts require you to define certain options to get a large off_t
instead of a small one, to get useful ftell and fseek calls instead of
ones that can only support 2GB files, and so on. This patch makes
Libevent support those platforms by:
* Defining the right options when we build, and
* Changing our API so that it does not depend on the platform's
definition of off_t.
Based on discusion with Michael Herf
Using --enable-gcc-hardening enables some additional safety features
that gcc makes available such as stack smashing protection using
canaries and ASLR.
This commit is based on a patch for Tor:
(git commit 04fa935e02270bc90aca0f1c652d31c7a872175b by Jacob Appelbaum)
Copyright (c) 2007-2011, The Tor Project, Inc.
This commit is based on a patch for Tor
(git commit ca60a6ce3f4786626ac455ec1b798b2e8304635c by Peter
Palfrader), Copyright (c) 2007-2011, The Tor Project, Inc.
(Originally, it added --enable-gcc-warnings-advisory as in Tor; Nick
changed that.)
Starting with Lion, Apple decided to deprecate the system openssl. We
can start requiring users to install their own openssl once OS X doesn't
ship with it anymore.
