Prevent Ada 202x Use in GNAT

GNAT allows the following code due to Random(Generator, First, Last) being implemented in the runtime, but it's not part of Ada 2012. Can I cause this to generate a compile error since it shouldn't be available?

with Ada.Text_IO; use Ada.Text_IO;
with Ada.Numerics.Discrete_Random;

procedure Main is
   package Positive_Random is new Ada.Numerics.Discrete_Random
     (Result_Subtype => Positive);
   Generator : Positive_Random.Generator;

   -- This should fail, since function isn't part of Ada 2012.
   Value : Positive := Positive_Random.Random (Generator, 1, 10);
    Put_Line (Value'Image);
end Main;

This is my gpr file:

project Default is

   for Source_Dirs use ("src");
   for Object_Dir use "obj";
   for Main use ("main.adb");

   package Compiler is
      for Switches ("ada") use ("-gnat12");
   end Compiler;

end Default;


  • In my point of view, the standard way to do this is to add a global restriction:

    pragma Restrictions (No_Implementation_Identifiers);


    There are no usage names that denote declarations with implementation-defined identifiers that occur within language-defined packages or instances of language-defined generic packages.

    But this doesn't work in GNAT Community Edition 2021 (nor in GCC 11, I guess).

    You can create a custom GNAT run-time and delete this subprogram or mark it with aspect Implementation_Defined to make the restriction work.