Fixes "searchaddpl" bug emitting bogus error "Bad position".

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1338

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1352

This enhances readability in sidebar, especially for "User’s Manual" and
"Protocol" pages

Fixes building with GCC 12.

With large "max_playlist_length" settings, the "data" array can be
very large, and initializing it during MPD startup causes page faults,
resulting in allocation of physical RAM.  This commit postpones the
initialization until the queue is really large, to avoid wasting
memory.

Signed-off-by: Shen-Ta Hsieh <ibmibmibm.tw@gmail.com>

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Signed-off-by: Rosen Penev <rosenp@gmail.com>

clang-tidy reports this is trivially copyable and thus std::move has no
effect.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

SonarLint reports the latter to be better:

std::scoped_lock basically provides the same feature as std::lock_guard,
but is more generic: It can lock several mutexes at the same time, with a
deadlock prevention mechanism (see {rule:cpp:S5524}). The equivalent code
to perform simultaneous locking with std::lock_guard is significantly more
complex. Therefore, it is simpler to use std::scoped_lock all the time,
even when locking only one mutex (there will be no performance impact).
Signed-off-by: Rosen Penev <rosenp@gmail.com>

C arrays can be used with make_unique in C++17.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Signed-off-by: Rosen Penev <rosenp@gmail.com>

This reverts commit 552c30ea.

It has caused various problems; for example, MPD wasn't able to write
the pid_file (which was already mitigated by commit a4e42172).

And apparently, the socket file created in the same directory by
mpd.socket disappears when mpd.service (re)creates the directory.  I
could not reproduce this problem with 247.3, but maybe this is a bug
in older systemd versions?

Until we figure out why this happens, let's remove the
RuntimeDirectory directive.  A future MPD version may be launched as
regular user, not as root, which will eliminate one major problem with
RuntimeDirectory.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1328

This fixes this build error observed with clang and -stdlib=libc++:

../mpd-0.23.3/src/output/plugins/PipeWireOutputPlugin.cxx:661:55: error: implicit instantiation of undefined template 'std::array<std::byte, 64>'
        std::array<std::byte, MAX_CHANNELS * MAX_INTERLEAVE> buffer;
                                                             ^
/usr/include/c++/v1/__tuple:219:64: note: template is declared here
template <class _Tp, size_t _Size> struct _LIBCPP_TEMPLATE_VIS array;
                                                               ^

For libavcodec 59 support.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1333

Add an option to the UPnP database plugin to configure which interface
is used by upnp to discover servers.

upnp by default selects the first interface that is not loopback, which
in some cases might not be the desired interface. For example if wanting
to access a DLNA server over a VPN connection.

The "interface" option can now be set to the name of the desired
interface to achieve this.

The default behaviour remains unchanged.

Adds the Interface Name as an argument to the *Init functions to make it
possible to select which interface is used by upnp to detect servers.

Currently "nullptr" is passed in to let the upnp library select an
interface, as before.

Commit 552c30ea caused problems for those people who still had a
"pid_file" setting (even though that is obsolete with systemd),
because now /run/mpd is owned by root:root (our mpd.service has no
User=mpd directive, so systemd starts MPD as root).

To work around this problem, and to be able to keep
RuntimeDirectory=mpd (which solved a problem of other MPD users), the
best compromise seems to just ignore the "pid_file" setting when it is
of no use.

This way, MPD can reliably detect whether it was started as systemd
service, which is better than checking sd_booted(), which only checks
whether systemd manages all services, but still MPD could be started
manually.