[Ada] Confusing warning on finalization actions during elaboration

[Pierre-Marie de Rodat <derodat at adacore dot com>]

This patch suppresses warnings concerning potential access-before-elaboration
issues when the warnings originate from finalization actions performed within
an initialization context. Such warnings seem confusing to users because they
are not directly related to source code, but to byproducts of the finalization
model in GNAT. Run time ABE checks are still installed in such cases.

------------
-- Source --
------------

--  pack.ads

with Ada.Finalization; use Ada.Finalization;

package Pack is
   type Ctrl is new Controlled with null record;

   procedure Finalize (Obj : in out Ctrl);
   procedure Initialize (Obj : in out Ctrl);

   function Elaborator return Boolean;
end Pack;

--  pack.adb

with Ada.Text_IO; use Ada.Text_IO;

package body Pack is
   procedure Initialize (Obj : in out Ctrl) is
   begin
      Put_Line ("ini");
      raise Program_Error;
   end Initialize;

   function Elaborator return Boolean is
   begin
      Put_Line ("elb");

      declare
         Obj : Ctrl;
      begin Put_Line ("ERROR: ABE not detected"); end;

      return True;
   exception
      when Program_Error =>
         Put_Line ("OK");
         return True;
   end Elaborator;

   Elab : constant Boolean := Elaborator;

   procedure Finalize (Obj : in out Ctrl) is
   begin
      Put_Line ("fin");
   end Finalize;
end Pack;

--  main.adb

with Pack;

procedure Main is begin null; end Main;

----------------------------
-- Compilation and output --
----------------------------

$ gnatmake -q main.adb
$ ./main
elb
ini
OK

Tested on x86_64-pc-linux-gnu, committed on trunk

2017-11-08  Hristian Kirtchev  <kirtchev@adacore.com>

	* sem_elab.adb (Ensure_Prior_Elaboration): Add new parameter
	In_Partial_Fin along with a comment on its usage. Do not guarantee the
	prior elaboration of a unit when the need came from a partial
	finalization context.
	(In_Initialization_Context): Relocated to Process_Call.
	(Is_Partial_Finalization_Proc): New routine.
	(Process_Access): Add new parameter In_Partial_Fin along with a comment
	on its usage.
	(Process_Activation_Call): Add new parameter In_Partial_Fin along with
	a comment on its usage.
	(Process_Activation_Conditional_ABE_Impl): Add new parameter
	In_Partial_Fin along with a comment on its usage. Do not emit any ABE
	diagnostics when the activation occurs in a partial finalization
	context.
	(Process_Activation_Guaranteed_ABE_Impl): Add new parameter
	In_Partial_Fin along with a comment on its usage.
	(Process_Call): Add new parameter In_Partial_Fin along with a comment
	on its usage. A call is within a partial finalization context when it
	targets a finalizer or primitive [Deep_]Finalize, and the call appears
	in initialization actions. Pass this information down to the recursive
	steps of the Processing phase.
	(Process_Call_Ada): Add new parameter In_Partial_Fin along with a
	comment on its usage. Remove the guard which suppresses the generation
	of implicit Elaborate[_All] pragmas. This is now done in
	Ensure_Prior_Elaboration.
	(Process_Call_Conditional_ABE): Add new parameter In_Partial_Fin along
	with a comment on its usage. Do not emit any ABE diagnostics when the
	call occurs in a partial finalization context.
	(Process_Call_SPARK): Add new parameter In_Partial_Fin along with a
	comment on its usage.
	(Process_Instantiation): Add new parameter In_Partial_Fin along with a
	comment on its usage.
	(Process_Instantiation_Ada): Add new parameter In_Partial_Fin along
	with a comment on its usage.
	(Process_Instantiation_Conditional_ABE): Add new parameter
	In_Partial_Fin along with a comment on its usage. Do not emit any ABE
	diagnostics when the instantiation occurs in a partial finalization
	context.
	(Process_Instantiation_SPARK): Add new parameter In_Partial_Fin along
	with a comment on its usage.
	(Process_Scenario): Add new parameter In_Partial_Fin along  with a
	comment on its usage.
	(Process_Single_Activation): Add new parameter In_Partial_Fin along
	with a comment on its usage.
	(Traverse_Body): Add new parameter In_Partial_Fin along with a comment
	on its usage.

Attachment: difs
Description: Text document