Merge branch '3421-glib_debug-docs' into 'main'

docs: Set -Dglib_debug=enabled by default and document it for distros

Closes #3421

See merge request GNOME/glib!4212

docs/macros.md

@@ -61,6 +61,10 @@ Quite a bit of additional debugging code is compiled into GLib when this
 macro is defined, and since it is a globally visible define, third-party code
 may be affected by it similarly to `G_DISABLE_ASSERT`.
 
+Some of these checks can be relatively expensive at runtime, as they affect
+every GObject type cast. Distributions are recommended to disable
+`G_ENABLE_DEBUG` in stable release builds.
+
 The additional code executed/compiled for this macro currently includes the
 following, but this is not an exhaustive list:
  - extra validity checks for `GDate`

meson.options

@@ -115,21 +115,21 @@ option('oss_fuzz',
 
 option('glib_debug',
        type : 'feature',
-       value : 'auto',
+       value : 'enabled',
        yield : true,
-       description : 'Enable GLib debug infrastructure (see docs/macros.txt)')
+       description : 'Enable GLib debug infrastructure (distros typically want this disabled in production; see docs/macros.md)')
 
 option('glib_assert',
        type : 'boolean',
        value : true,
        yield : true,
-       description : 'Enable GLib assertion (see docs/macros.txt)')
+       description : 'Enable GLib assertion (see docs/macros.md)')
 
 option('glib_checks',
        type : 'boolean',
        value : true,
        yield : true,
-       description : 'Enable GLib checks such as API guards (see docs/macros.txt)')
+       description : 'Enable GLib checks such as API guards (see docs/macros.md)')
 
 option('libelf',
        type : 'feature',