Determining if OpenSSL structures are opaque now uses an autoconf check
instead of comparing the version number. Some definitions have been
moved to their own check as assumptions which were true for OpenSSL
with opaque structures did not hold for LibreSSL. Closes ticket 21359.
Apple is supposed to decorate their function declarations with
macros to indicate which OSX version introduced them, so that you
can tell the compiler that you want to build against certain
versions of OSX. But they forgot to do that for clock_gettime() and
getentropy(), both of which they introduced in 10.12.
This patch adds a kludge to the configure.ac script where, if we
detect that we are targeting OSX 10.11 or earlier, we don't even probe
to see if the two offending functions are present.
Closes ticket 20235.
Closes ticket 20303.
The LIBRESSL_VERSION_NUMBER check is needed because if our openssl
is really libressl, it will have an openssl version number we can't
really believe.
OpenBSD removes this function, and now that Tor requires Libevent 2,
we should also support the OpenBSD Libevent 2.
Fixes bug 19904; bugfix on 0.2.5.4-alpha.
Only some very ancient distributions don't ship with Libevent 2 anymore,
even the oldest supported Ubuntu LTS version has it. This allows us to
get rid of a lot of compat code.
The Autoconf macro AC_USE_SYSTEM_EXTENSIONS defines preprocessor macros
which turn on extensions to C and POSIX. The macro also makes it easier
for developers to use the extensions without needing (or forgetting) to
define them manually.
The macro can be safely used because it was introduced in Autoconf 2.60
and Tor requires Autoconf 2.63 and above.
