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From: "Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Dueling Compilers
Date: Wed, 25 Nov 2020 15:08:40 +0100
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Consider the package

with Ada.Containers.Bounded_Doubly_Linked_Lists;

generic
    type E is private;
package Preelaborable is
    package EL is new Ada.Containers.Bounded_Doubly_Linked_Lists
       (Element_Type => E);
end Preelaborable;

Two Ada-12 compilers give different results on this. Compiler G accepts it 
without problem. Compiler O rejects it with the error message

preelaborable.ads: Error: line 6 col82 LRM:10.2.1(11.8/2), If a pragma 
Preelaborable_Initialization has been applied to the generic formal, the 
corresponding actual type must have preelaborable initialization

AFAICT from the ARM, the generic formal Element_Type of 
Ada.Containers.Bounded_Doubly_Linked_Lists does not have pragma 
Preelaborable_Initialization applied to it. However, the type List, which 
probably has [sub]components of Element_Type, does.

Which compiler is correct? What is the intent of the ARM?

-- 
Jeff Carter
"Apart from the sanitation, the medicine, education, wine,
public order, irrigation, roads, the fresh water system,
and public health, what have the Romans ever done for us?"
Monty Python's Life of Brian
80