Syntax:
pragma Extensions_Allowed (On | Off | All_Extensions);
This configuration pragma enables (via the “On” or “All_Extensions” argument)
or disables (via the “Off” argument) the implementation extension mode; the
pragma takes precedence over the -gnatX and -gnatX0 command switches.
If an argument of "On" is specified, the latest version of the Ada language
is implemented (currently Ada 2022) and, in addition, a curated set of GNAT
specific extensions are recognized. (See the list here
here)
An argument of "All_Extensions" has the same effect except that some extra
experimental extensions are enabled (See the list here
here)