gtkdoc-scan 1.32 performs stricter checks on structures definitions and so it complains on:
/build/networkmanager/src/NetworkManager/libnm/./nm-vpn-plugin-old.h:0: warning: partial declaration (struct) : typedef struct {
NM_DEPRECATED_IN_1_2
GObject parent;
} NMVpnPluginOld NM_DEPRECATED_IN_1_2;because of the unrecognized token NM_DEPRECATED_IN_1_2.
Pass all allowed macros to gtkdoc-scan through the --ignore-decorators argument.
https://gitlab.gnome.org/GNOME/gtk-doc/issues/98 #238 (closed)