"DEFAULT" is a bad name - all it says is that it's the default value,
but it doesn't say what it means.  The name NOTICE mimics the syslog
level.

This makes ccache more efficient when recompiling with different
plugins.

Found with readability-uppercase-literal-suffix
Signed-off-by: Rosen Penev <rosenp@gmail.com>

The former was deprecated with C++14.

According to the C++11 and C++17 standards, both files are identical.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with readability-uppercase-literal-suffix
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-redundant-void-arg
Signed-off-by: Rosen Penev <rosenp@gmail.com>

This is the correct thing to do for ports from which a signal ultimately
"originates", such as is the case with mpd.

Without this, the compiler may optimize accesses away.

Without this, the compiler may optimize accesses away.

The JACK output plugin would not correctly upmix mono input files when exactly 2 output ports were configured. This fixes that.

Adds missing checks to several plugins.

Coverity discovered that the Pulse plugin could throw exceptions from
Pause(), but that method was marked "noexcept" because its caller was
not designed to catch exceptions.  So instead of avoiding exceptions
(by catching and logging them in each and every implementation), let's
allow them, and do the catch/log game in the MPD core.

Yet another C-style vtable replaced with C++.

Hide struct FilteredAudioOutput from the plugins, preparing for hiding
MPD's core internals.

Prepare to add an abstract class AudioOutput, to be implemented by
plugins, to get rid of the C-style vtable.

This allows removing the "base.pause" check from the JACK output
plugin, and will allow removing similar accesses from other plugins.

This eliminates some overhead, because the compiler doesn't need to
consider these functions throwing.

Eliminate dependency on io_thread_get().