ada: Fix missing finalization in library-unit instance spec

This fixes the missing finalization of objects declared in the spec of
package instances that are library units (and only them, i.e. not all
library-level package instances) when the instances have a package body.

The finalization is done when there is no package body, and supporting
this case precisely broke the other case because of a thinko or a typo.

This also requires a small adjustment to the routine writing ALI files.

gcc/ada/

	* exp_ch7.adb (Build_Finalizer): Reverse the test comparing the
	instantiation and declaration nodes of a package instance, and
	therefore bail out only when they are equal.  Adjust comments.
	(Expand_N_Package_Declaration): Do not clear the Finalizer field.
	* lib-writ.adb: Add with and use clauses for Sem_Util.
	(Write_Unit_Information): Look at unit nodes to find finalizers.
	* sem_ch12.adb (Analyze_Package_Instantiation): Beef up the comment
	about the rewriting of the instantiation node into a declaration.

3 files changed, 34 insertions, 13 deletions

diff --git a/gcc/ada/exp_ch7.adb b/gcc/ada/exp_ch7.adb
index 7ea39f7..a02e28e 100644
--- a/gcc/ada/exp_ch7.adb
+++ b/gcc/ada/exp_ch7.adb
@@ -3534,15 +3534,21 @@ package body Exp_Ch7 is
         and then
           (not Is_Library_Level_Entity (Spec_Id)
 
-            --  Nested packages are library level entities, but do not need to
+            --  Nested packages are library-level entities, but do not need to
             --  be processed separately.
 
             or else Scope_Depth (Spec_Id) /= Uint_1
+
+            --  Do not build two finalizers for an instance without body that
+            --  is a library unit (see Analyze_Package_Instantiation).
+
             or else (Is_Generic_Instance (Spec_Id)
-                      and then Package_Instantiation (Spec_Id) /= N))
+                      and then Package_Instantiation (Spec_Id) = N))
 
-         --  Still need to process package body instantiations which may
-         --  contain objects requiring finalization.
+         --  Still need to process library-level package body instances, whose
+         --  instantiation was deferred and thus could not be seen during the
+         --  processing of the enclosing scope, and which may contain objects
+         --  requiring finalization.
 
         and then not
           (For_Package_Body
@@ -5376,7 +5382,9 @@ package body Exp_Ch7 is
             Defer_Abort => False,
             Fin_Id      => Fin_Id);
 
-         Set_Finalizer (Id, Fin_Id);
+         if Present (Fin_Id) then
+            Set_Finalizer (Id, Fin_Id);
+         end if;
       end if;
 
       --  If this is a library-level package and unnesting is enabled,
diff --git a/gcc/ada/lib-writ.adb b/gcc/ada/lib-writ.adb
index deecfc0..23b6266 100644
--- a/gcc/ada/lib-writ.adb
+++ b/gcc/ada/lib-writ.adb
@@ -50,6 +50,7 @@ with Rident;         use Rident;
 with Stand;          use Stand;
 with Scn;            use Scn;
 with Sem_Eval;       use Sem_Eval;
+with Sem_Util;       use Sem_Util;
 with Sinfo;          use Sinfo;
 with Sinfo.Nodes;    use Sinfo.Nodes;
 with Sinfo.Utils;    use Sinfo.Utils;
@@ -524,10 +525,20 @@ package body Lib.Writ is
          Write_Info_Str (" O");
          Write_Info_Char (OA_Setting (Unit_Num));
 
-         if Ekind (Uent) in E_Package | E_Package_Body
-           and then Present (Finalizer (Uent))
-         then
-            Write_Info_Str (" PF");
+         --  For a package instance with a body that is a library unit, the two
+         --  compilation units share Cunit_Entity so we cannot rely on Uent.
+
+         if Ukind in N_Package_Declaration | N_Package_Body then
+            declare
+               E : constant Entity_Id := Defining_Entity (Unit (Unode));
+
+            begin
+               if Ekind (E) in E_Package | E_Package_Body
+                 and then Present (Finalizer (E))
+               then
+                  Write_Info_Str (" PF");
+               end if;
+            end;
          end if;
 
          if Is_Preelaborated (Uent) then
diff --git a/gcc/ada/sem_ch12.adb b/gcc/ada/sem_ch12.adb
index 181392c..c31d0c6 100644
--- a/gcc/ada/sem_ch12.adb
+++ b/gcc/ada/sem_ch12.adb
@@ -5007,10 +5007,12 @@ package body Sem_Ch12 is
          Set_First_Private_Entity (Defining_Unit_Name (Unit_Renaming),
            First_Private_Entity (Act_Decl_Id));
 
-         --  If the instantiation will receive a body, the unit will be
-         --  transformed into a package body, and receive its own elaboration
-         --  entity. Otherwise, the nature of the unit is now a package
-         --  declaration.
+         --  If the instantiation needs a body, the unit will be turned into
+         --  a package body and receive its own elaboration entity. Otherwise,
+         --  the nature of the unit is now a package declaration.
+
+         --  Note that the below rewriting means that Act_Decl, which has been
+         --  analyzed and expanded, will be re-expanded as the rewritten N.
 
          if Nkind (Parent (N)) = N_Compilation_Unit
            and then not Needs_Body