Instead of having a file segment born as one type and stay that way
forever, let them start out unmapped, but map themselves as needed
if they need to get written out on a non-drains_to_fd evbuffer.
The sendfile() implementation for evbuffer_add_file is potentially more
efficient, but it has a problem: you can only use it to send bytes over
a socket using sendfile(). If you are writing bytes via SSL_send() or
via a filter, or if you need to be able to inspect your buffer, it
doesn't work.
As an easy fix, this patch disables the sendfile-based implementation of
evbuffer_add_file on an evbuffer unless the user sets a new
EVBUFFER_FLAG_DRAINS_TO_FD flag on that evbuffer, indicating that the
evbuffer will not be inspected, but only written out via
evbuffer_write(), evbuffer_write_atmost(), or drained with stuff like
evbuffer_drain() or evbuffer_add_buffer(). This flag is off by
default, except for evbuffers used for output on bufferevent_socket.
In the future, it could be interesting to make a best-effort file
segment implementation that tries to send via sendfile, but mmaps on
demand. That's too much complexity for a stable release series, though.
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.)
