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);
begin 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;1 Answer
In my point of view, the standard way to do this is to add a global restriction:
pragma Restrictions (No_Implementation_Identifiers);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.
