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>

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>

Since we switched from autotools to Meson in commit
94592c14, we don't need to include
`config.h` early to properly enable large file support.  Meson passes
the required macros on the compiler command line instead of defining
them in `config.h`.

This means we can include `config.h` at any time, whenever we want to
check its macros, and there are no ordering constraints.

Fix breakage from commit bea5681f

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

The old struct config_param remains only for top-level string options.

Use a listener interface instead of GlobalEvents.

Passing a void pointer is unsafe.

Prepare to migrate away from GLib.  Currently, we're still using GLib
as a backend.

Replaces GLib's GError.

Mixers with the "global" flag set aren't closed automatically when the
output device is closed.  Thus, they might still be open when MPD
shuts down.

After we've been hit by Large File Support problems several times in
the past week (which only occur on 32 bit platforms, which I don't
have), this is yet another attempt to fix the issue.

A mixer is useful enough if it can be read.  Setting it may be
found unavailable at runtime.

If the method get_volume() returns -1 and no error object is set, then
the volume is currently unavailable, but the mixer should not be
closed immediately.

It's possible to have a mixer implementation which does not explicitly
need the methods open() and close().

This allows the mixer object to access its associated audio output
object.