2010-06-18 Thomas Quinot <quinot@adacore.com>

	* types.ads: Clean up obsolete comments
	* tbuild.adb: Minor reformatting.
	* exp_ch5.adb, sem_intr.adb, sem_ch10.adb, rtsfind.adb, s-shasto.adb,
	exp_strm.adb, aa_drive.adb: Minor reformatting.
	* sem_res.adb (Is_Predefined_Operator): An operator that is an imported
	intrinsic with an Interface_Name denotes an imported back-end builtin,
	and must be rewritten into a call, not left in the tree as an operator,
	so return False in that case.

2010-06-18  Eric Botcazou  <ebotcazou@adacore.com>

	* exp_util.adb (Remove_Side_Effects): Make a copy for an allocator.
	
2010-06-18  Robert Dewar  <dewar@adacore.com>

	* scos.ads: Add proposed output for case expression

2010-06-18  Jose Ruiz  <ruiz@adacore.com>

	* gnat_ugn.texi: Document that, when using the RTX compiler to generate
	RTSS modules, we need to use the Microsoft linker.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@160974 138bc75d-0d04-0410-961f-82ee72b054a4

13 files changed, 149 insertions, 82 deletions

diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog
index f76b284c1d6..e48bac3e0c2 100644
--- a/gcc/ada/ChangeLog
+++ b/gcc/ada/ChangeLog
@@ -1,3 +1,27 @@
+2010-06-18  Thomas Quinot  <quinot@adacore.com>
+
+	* types.ads: Clean up obsolete comments
+	* tbuild.adb: Minor reformatting.
+	* exp_ch5.adb, sem_intr.adb, sem_ch10.adb, rtsfind.adb, s-shasto.adb,
+	exp_strm.adb, aa_drive.adb: Minor reformatting.
+	* sem_res.adb (Is_Predefined_Operator): An operator that is an imported
+	intrinsic with an Interface_Name denotes an imported back-end builtin,
+	and must be rewritten into a call, not left in the tree as an operator,
+	so return False in that case.
+
+2010-06-18  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* exp_util.adb (Remove_Side_Effects): Make a copy for an allocator.
+	
+2010-06-18  Robert Dewar  <dewar@adacore.com>
+
+	* scos.ads: Add proposed output for case expression
+
+2010-06-18  Jose Ruiz  <ruiz@adacore.com>
+
+	* gnat_ugn.texi: Document that, when using the RTX compiler to generate
+	RTSS modules, we need to use the Microsoft linker.
+
 2010-06-18  Robert Dewar  <dewar@adacore.com>
 
 	* checks.adb (Safe_To_Capture_In_Parameter_Value): Deal with case
diff --git a/gcc/ada/exp_ch5.adb b/gcc/ada/exp_ch5.adb
index 2cdb9c8111d..71b58ae358e 100644
--- a/gcc/ada/exp_ch5.adb
+++ b/gcc/ada/exp_ch5.adb
@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 B o d y                                  --
 --                                                                          --
---          Copyright (C) 1992-2009, Free Software Foundation, Inc.         --
+--          Copyright (C) 1992-2010, Free Software Foundation, Inc.         --
 --                                                                          --
 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
 -- terms of the  GNU General Public License as published  by the Free Soft- --
@@ -4192,9 +4192,9 @@ package body Exp_Ch5 is
          end;
       end if;
 
-      --  If we are returning an object that may not be bit-aligned, then
-      --  copy the value into a temporary first. This copy may need to expand
-      --  to a loop of component operations..
+      --  If we are returning an object that may not be bit-aligned, then copy
+      --  the value into a temporary first. This copy may need to expand to a
+      --  loop of component operations.
 
       if Is_Possibly_Unaligned_Slice (Exp)
         or else Is_Possibly_Unaligned_Object (Exp)
diff --git a/gcc/ada/exp_strm.adb b/gcc/ada/exp_strm.adb
index 42c34a8487e..ddb1064c475 100644
--- a/gcc/ada/exp_strm.adb
+++ b/gcc/ada/exp_strm.adb
@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 B o d y                                  --
 --                                                                          --
---          Copyright (C) 1992-2008, Free Software Foundation, Inc.         --
+--          Copyright (C) 1992-2010, Free Software Foundation, Inc.         --
 --                                                                          --
 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
 -- terms of the  GNU General Public License as published  by the Free Soft- --
@@ -1396,7 +1396,7 @@ package body Exp_Strm is
             --  If the enclosing record is an unchecked_union, we use the
             --  default expressions for the discriminant (it must exist)
             --  because we cannot generate a reference to it, given that
-            --  it is not stored..
+            --  it is not stored.
 
             if Is_Unchecked_Union (Scope (Entity (Name (VP)))) then
                D_Ref :=
diff --git a/gcc/ada/exp_util.adb b/gcc/ada/exp_util.adb
index e8a85103be8..95036b9e726 100644
--- a/gcc/ada/exp_util.adb
+++ b/gcc/ada/exp_util.adb
@@ -4684,14 +4684,15 @@ package body Exp_Util is
       Scope_Suppress := (others => True);
 
       --  If it is a scalar type and we need to capture the value, just make
-      --  a copy. Likewise for a function call, an attribute reference or an
-      --  operator. And if we have a volatile reference and Name_Req is not
-      --  set (see comments above for Side_Effect_Free).
+      --  a copy. Likewise for a function call, an attribute reference, an
+      --  allocator or an operator. And if we have a volatile reference and
+      --  Name_Req is not set (see comments above for Side_Effect_Free).
 
       if Is_Elementary_Type (Exp_Type)
         and then (Variable_Ref
                    or else Nkind (Exp) = N_Function_Call
                    or else Nkind (Exp) = N_Attribute_Reference
+                   or else Nkind (Exp) = N_Allocator
                    or else Nkind (Exp) in N_Op
                    or else (not Name_Req and then Is_Volatile_Reference (Exp)))
       then
diff --git a/gcc/ada/gnat_ugn.texi b/gcc/ada/gnat_ugn.texi
index 274dc8c4662..0681deaab2d 100644
--- a/gcc/ada/gnat_ugn.texi
+++ b/gcc/ada/gnat_ugn.texi
@@ -25555,7 +25555,8 @@ Windows executables that run in Ring 3 to utilize memory protection
 @item
 Real-time subsystem (RTSS) executables that run in Ring 0, where
 performance can be optimized with RTSS applications taking precedent
-over all Windows applications (@emph{rts-rtx-rtss}).
+over all Windows applications (@emph{rts-rtx-rtss}). This mode requires
+the Microsoft linker to handle RTSS libraries.
 
 @end itemize
 
diff --git a/gcc/ada/rtsfind.adb b/gcc/ada/rtsfind.adb
index 32323fc593e..9742cb20b95 100644
--- a/gcc/ada/rtsfind.adb
+++ b/gcc/ada/rtsfind.adb
@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 B o d y                                  --
 --                                                                          --
---          Copyright (C) 1992-2009, Free Software Foundation, Inc.         --
+--          Copyright (C) 1992-2010, Free Software Foundation, Inc.         --
 --                                                                          --
 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
 -- terms of the  GNU General Public License as published  by the Free Soft- --
@@ -1333,8 +1333,8 @@ package body Rtsfind is
                --  The RT_Unit_Table entry that may need updating
 
             begin
-               --  If entry is not set, set it now, and indicate that it
-               --  was loaded through an explicit context clause..
+               --  If entry is not set, set it now, and indicate that it was
+               --  loaded through an explicit context clause.
 
                if No (U.Entity) then
                   U := (Entity               => E,
diff --git a/gcc/ada/s-shasto.adb b/gcc/ada/s-shasto.adb
index 7038d796c28..783fdc4a95d 100644
--- a/gcc/ada/s-shasto.adb
+++ b/gcc/ada/s-shasto.adb
@@ -6,8 +6,8 @@
 --                                                                          --
 --                                 B o d y                                  --
 --                                                                          --
---          Copyright (C) 1998-2009, Free Software Foundation, Inc.         --
---                                                                         --
+--          Copyright (C) 1998-2010, Free Software Foundation, Inc.         --
+--                                                                          --
 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
 -- terms of the  GNU General Public License as published  by the Free Soft- --
 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
@@ -88,8 +88,8 @@ package body System.Shared_Storage is
       Item   : AS.Stream_Element_Array);
 
    subtype Hash_Header is Natural range 0 .. 30;
-   --  Number of hash headers, related (for efficiency purposes only)
-   --  to the maximum number of lock files..
+   --  Number of hash headers, related (for efficiency purposes only) to the
+   --  maximum number of lock files.
 
    type Shared_Var_File_Entry;
    type Shared_Var_File_Entry_Ptr is access Shared_Var_File_Entry;
diff --git a/gcc/ada/scos.ads b/gcc/ada/scos.ads
index dc02e28c5e0..ce865d77587 100644
--- a/gcc/ada/scos.ads
+++ b/gcc/ada/scos.ads
@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 S p e c                                  --
 --                                                                          --
---             Copyright (C) 2009, Free Software Foundation, Inc.           --
+--          Copyright (C) 2009-2010, Free Software Foundation, Inc.         --
 --                                                                          --
 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
 -- terms of the  GNU General Public License as published  by the Free Soft- --
@@ -161,9 +161,9 @@ package SCOs is
 
    --    and is omitted for all other cases.
 
-   --  Note: up to 6 entries can appear on a single CS line. If more than 6
-   --  entries appear in one logical statement sequence, continuation lines are
-   --  marked by Cs and appear immediately after the CS line they continue.
+   --    Note: up to 6 entries can appear on a single CS line. If more than 6
+   --    entries appear in one logical statement sequence, continuation lines
+   --    are marked by Cs and appear immediately after the CS line.
 
    --  Decisions
 
@@ -272,6 +272,23 @@ package SCOs is
    --    enclosing statement. The SCO line for a nested decision always occurs
    --    after the line for the enclosing decision.
 
+   --  Case Expressions
+
+   --    For case statements, we rely on statement coverage to make sure that
+   --    all branches of a case statement are covered, but that does not work
+   --    for case expressions, since the entire expression is contained in a
+   --    single statement. However, for complete coverage we really should be
+   --    able to check that every branch of the case statement is covered, so
+   --    we generate a SCO of the form:
+
+   --      CC sloc-range sloc-range ...
+
+   --    where sloc-range covers the range of the case expression.
+
+   --    Note: up to 6 entries can appear on a single CC line. If more than 6
+   --    entries appear in one logical statement sequence, continuation lines
+   --    are marked by Cc and appear immediately after the CC line.
+
    ---------------------------------------------------------------------
    -- Internal table used to store Source Coverage Obligations (SCOs) --
    ---------------------------------------------------------------------
diff --git a/gcc/ada/sem_ch10.adb b/gcc/ada/sem_ch10.adb
index 6b61a875763..e5a42d669f2 100644
--- a/gcc/ada/sem_ch10.adb
+++ b/gcc/ada/sem_ch10.adb
@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 B o d y                                  --
 --                                                                          --
---          Copyright (C) 1992-2009, Free Software Foundation, Inc.         --
+--          Copyright (C) 1992-2010, Free Software Foundation, Inc.         --
 --                                                                          --
 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
 -- terms of the  GNU General Public License as published  by the Free Soft- --
@@ -552,7 +552,8 @@ package body Sem_Ch10 is
                                      or else
                                        Used_In_Spec)
                      then
-                        Error_Msg_N ("?redundant with clause in body", Clause);
+                        Error_Msg_N -- CODEFIX
+                          ("?redundant with clause in body", Clause);
                      end if;
 
                      Used_In_Body := False;
@@ -580,7 +581,8 @@ package body Sem_Ch10 is
                        Exit_On_Self => True);
 
                      if Withed then
-                        Error_Msg_N ("?redundant with clause", Clause);
+                        Error_Msg_N -- CODEFIX
+                          ("?redundant with clause", Clause);
                      end if;
                   end;
                end if;
@@ -690,9 +692,9 @@ package body Sem_Ch10 is
             end if;
 
             if Circularity then
-               Error_Msg_N
+               Error_Msg_N -- CODEFIX???
                  ("circular dependency caused by with_clauses", N);
-               Error_Msg_N
+               Error_Msg_N -- CODEFIX???
                  ("\possibly missing limited_with clause"
                   & " in one of the following", N);
 
@@ -1470,11 +1472,11 @@ package body Sem_Ch10 is
                                                       Unit_Name)
                               then
                                  Error_Msg_Sloc := Sloc (It);
-                                 Error_Msg_N
+                                 Error_Msg_N -- CODEFIX???
                                    ("simultaneous visibility of limited "
                                     & "and unlimited views not allowed",
                                     Item);
-                                 Error_Msg_NE
+                                 Error_Msg_NE -- CODEFIX???
                                    ("\unlimited view visible through "
                                     & "context clause #",
                                     Item, It);
@@ -1853,7 +1855,8 @@ package body Sem_Ch10 is
       if No (Nam)
         or else not Is_Protected_Type (Etype (Nam))
       then
-         Error_Msg_N ("missing specification for Protected body", N);
+         Error_Msg_N -- CODEFIX???
+           ("missing specification for Protected body", N);
       else
          Set_Scope (Defining_Entity (N), Current_Scope);
          Set_Has_Completion (Etype (Nam));
@@ -2252,7 +2255,8 @@ package body Sem_Ch10 is
       end if;
 
       if No (Nam) or else not Is_Task_Type (Etype (Nam)) then
-         Error_Msg_N ("missing specification for task body", N);
+         Error_Msg_N -- CODEFIX???
+           ("missing specification for task body", N);
       else
          Set_Scope (Defining_Entity (N), Current_Scope);
          Generate_Reference (Nam, Defining_Identifier (N), 'b');
@@ -2393,13 +2397,15 @@ package body Sem_Ch10 is
 
             begin
                if U_Kind = Implementation_Unit then
-                  Error_Msg_F ("& is an internal 'G'N'A'T unit?", Name (N));
+                  Error_Msg_F -- CODEFIX???
+                    ("& is an internal 'G'N'A'T unit?", Name (N));
 
                   --  Add alternative name if available, otherwise issue a
                   --  general warning message.
 
                   if Error_Msg_Strlen /= 0 then
-                     Error_Msg_F ("\use ""~"" instead", Name (N));
+                     Error_Msg_F -- CODEFIX???
+                       ("\use ""~"" instead", Name (N));
                   else
                      Error_Msg_F
                        ("\use of this unit is non-portable " &
@@ -3449,7 +3455,7 @@ package body Sem_Ch10 is
                      end loop;
 
                      if E2 = WEnt then
-                        Error_Msg_N
+                        Error_Msg_N -- CODEFIX???
                           ("unlimited view visible through use clause ", W);
                         return;
                      end if;
@@ -3799,7 +3805,7 @@ package body Sem_Ch10 is
                                          N_Generic_Package_Declaration)
         and then Nkind (Lib_Unit) not in N_Generic_Renaming_Declaration
       then
-         Error_Msg_N
+         Error_Msg_N -- CODEFIX???
            ("child of a generic package must be a generic unit", Lib_Unit);
 
       elsif not Is_Package_Or_Generic_Package (P_Name) then
@@ -4491,11 +4497,11 @@ package body Sem_Ch10 is
                         --  installed.
 
                         if Kind = N_Package_Declaration then
-                           Error_Msg_N
+                           Error_Msg_N -- CODEFIX???
                              ("simultaneous visibility of the limited and " &
                               "unlimited views not allowed", N);
                            Error_Msg_Sloc := Sloc (Item);
-                           Error_Msg_NE
+                           Error_Msg_NE -- CODEFIX???
                              ("\\  unlimited view of & visible through the " &
                               "context clause #", N, P);
                            Error_Msg_Sloc := Sloc (Decl);
@@ -5948,9 +5954,9 @@ package body Sem_Ch10 is
          if Nkind (Item) = N_With_Clause
            and then Private_Present (Item)
          then
-            --  If private_with_clause is redundant, remove it from
-            --  context, as a small optimization to subsequent handling
-            --  of private_with clauses in other nested packages..
+            --  If private_with_clause is redundant, remove it from context,
+            --  as a small optimization to subsequent handling of private_with
+            --  clauses in other nested packages.
 
             if In_Regular_With_Clause (Entity (Name (Item))) then
                declare
diff --git a/gcc/ada/sem_intr.adb b/gcc/ada/sem_intr.adb
index e5c779f1d7d..20a1614fb06 100644
--- a/gcc/ada/sem_intr.adb
+++ b/gcc/ada/sem_intr.adb
@@ -53,8 +53,8 @@ package body Sem_Intr is
    --  returns type String.
 
    procedure Check_Intrinsic_Operator (E : Entity_Id; N : Node_Id);
-   --  Check that operator is one of the binary arithmetic operators, and
-   --  that the types involved both have underlying integer types.
+   --  Check that operator is one of the binary arithmetic operators, and that
+   --  the types involved both have underlying integer types.
 
    procedure Check_Shift (E : Entity_Id; N : Node_Id);
    --  Check intrinsic shift subprogram, the two arguments are the same
diff --git a/gcc/ada/sem_res.adb b/gcc/ada/sem_res.adb
index 7fb17fd08a2..287a940e646 100644
--- a/gcc/ada/sem_res.adb
+++ b/gcc/ada/sem_res.adb
@@ -130,10 +130,14 @@ package body Sem_Res is
    --  declaration, and not an (anonymous) allocator type.
 
    function Is_Predefined_Op (Nam : Entity_Id) return Boolean;
-   --  Utility to check whether the name in the call is a predefined
-   --  operator, in which case the call is made into an operator node.
-   --  An instance of an intrinsic conversion operation may be given
-   --  an operator name, but is not treated like an operator.
+   --  Utility to check whether the entity for an operator is a predefined
+   --  operator, in which case the expression is left as an operator in the
+   --  tree (else it is rewritten into a call). An instance of an intrinsic
+   --  conversion operation may be given an operator name, but is not treated
+   --  like an operator. Note that an operator that is an imported back-end
+   --  builtin has convention Intrinsic, but is expected to be rewritten into
+   --  a call, so such an operator is not treated as predefined by this
+   --  predicate.
 
    procedure Replace_Actual_Discriminants (N : Node_Id; Default : Node_Id);
    --  If a default expression in entry call N depends on the discriminants
@@ -213,6 +217,9 @@ package body Sem_Res is
    procedure Resolve_Intrinsic_Operator (N : Node_Id; Typ : Entity_Id);
    --  A call to a user-defined intrinsic operator is rewritten as a call
    --  to the corresponding predefined operator, with suitable conversions.
+   --  Note that this applies only for intrinsic operators that denote
+   --  predefined operators, not opeartors that are intrinsic imports of
+   --  back-end builtins.
 
    procedure Resolve_Intrinsic_Unary_Operator (N : Node_Id; Typ : Entity_Id);
    --  Ditto, for unary operators (arithmetic ones and "not" on signed
@@ -1108,11 +1115,21 @@ package body Sem_Res is
 
    function Is_Predefined_Op (Nam : Entity_Id) return Boolean is
    begin
-      return Is_Intrinsic_Subprogram (Nam)
-        and then not Is_Generic_Instance (Nam)
+      --  Predefined operators are intrinsic subprograms
+
+      if not Is_Intrinsic_Subprogram (Nam) then
+         return False;
+      end if;
+
+      --  A call to a back-end builtin is never a predefined operator
+
+      if Is_Imported (Nam) and then Present (Interface_Name (Nam)) then
+         return False;
+      end if;
+
+      return not Is_Generic_Instance (Nam)
         and then Chars (Nam) in Any_Operator_Name
-        and then (No (Alias (Nam))
-                   or else Is_Predefined_Op (Alias (Nam)));
+        and then (No (Alias (Nam)) or else Is_Predefined_Op (Alias (Nam)));
    end Is_Predefined_Op;
 
    -----------------------------
diff --git a/gcc/ada/tbuild.adb b/gcc/ada/tbuild.adb
index b92854ec29d..ed9a7138c43 100644
--- a/gcc/ada/tbuild.adb
+++ b/gcc/ada/tbuild.adb
@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 B o d y                                  --
 --                                                                          --
---          Copyright (C) 1992-2009, Free Software Foundation, Inc.         --
+--          Copyright (C) 1992-2010, Free Software Foundation, Inc.         --
 --                                                                          --
 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
 -- terms of the  GNU General Public License as published  by the Free Soft- --
@@ -659,7 +659,7 @@ package body Tbuild is
 
          --  We don't really need these shift operators, since they never
          --  appear as operators in the source, but the path of least
-         --  resistance is to put them in (the aggregate must be complete)
+         --  resistance is to put them in (the aggregate must be complete).
 
          N_Op_Rotate_Left            => Name_Rotate_Left,
          N_Op_Rotate_Right           => Name_Rotate_Right,
diff --git a/gcc/ada/types.ads b/gcc/ada/types.ads
index 5467f4efe9c..42004ae2654 100644
--- a/gcc/ada/types.ads
+++ b/gcc/ada/types.ads
@@ -348,16 +348,16 @@ package Types is
    --  lie in. Such tests appear only in the lowest level packages.
 
    subtype List_Range      is Union_Id
-     range List_Low_Bound   .. List_High_Bound;
+     range List_Low_Bound    .. List_High_Bound;
 
    subtype Node_Range      is Union_Id
-     range Node_Low_Bound   .. Node_High_Bound;
+     range Node_Low_Bound    .. Node_High_Bound;
 
    subtype Elist_Range     is Union_Id
-     range Elist_Low_Bound  .. Elist_High_Bound;
+     range Elist_Low_Bound   .. Elist_High_Bound;
 
    subtype Elmt_Range      is Union_Id
-     range Elmt_Low_Bound   .. Elmt_High_Bound;
+     range Elmt_Low_Bound    .. Elmt_High_Bound;
 
    subtype Names_Range     is Union_Id
      range Names_Low_Bound   .. Names_High_Bound;
@@ -369,23 +369,23 @@ package Types is
      range Uint_Low_Bound    .. Uint_High_Bound;
 
    subtype Ureal_Range     is Union_Id
-     range Ureal_Low_Bound    .. Ureal_High_Bound;
+     range Ureal_Low_Bound   .. Ureal_High_Bound;
 
-   ----------------------------
+   -----------------------------
    -- Types for Atree Package --
-   ----------------------------
+   -----------------------------
 
    --  Node_Id values are used to identify nodes in the tree. They are
-   --  subscripts into the Node table declared in package Tree. Note that
-   --  the special values Empty and Error are subscripts into this table,
+   --  subscripts into the Nodes table declared in package Atree. Note that
+   --  the special values Empty and Error are subscripts into this table.
    --  See package Atree for further details.
 
    type Node_Id is range Node_Low_Bound .. Node_High_Bound;
    --  Type used to identify nodes in the tree
 
    subtype Entity_Id is Node_Id;
-   --  A synonym for node types, used in the entity package to refer to nodes
-   --  that are entities (i.e. nodes with an Nkind of N_Defining_xxx) All such
+   --  A synonym for node types, used in the Einfo package to refer to nodes
+   --  that are entities (i.e. nodes with an Nkind of N_Defining_xxx). All such
    --  nodes are extended nodes and these are the only extended nodes, so that
    --  in practice entity and extended nodes are synonymous.
 
@@ -402,12 +402,12 @@ package Types is
 
    Empty_List_Or_Node : constant := 0;
    --  This constant is used in situations (e.g. initializing empty fields)
-   --  where the value set will be used to represent either an empty node
-   --  or a non-existent list, depending on the context.
+   --  where the value set will be used to represent either an empty node or
+   --  a non-existent list, depending on the context.
 
    Error : constant Node_Id := Node_Low_Bound + 1;
-   --  Used to indicate that there was an error in the source program. A node
-   --  is actually allocated at this address, so that Nkind (Error) = N_Error.
+   --  Used to indicate an error in the source program. A node is actually
+   --  allocated with this Id value, so that Nkind (Error) = N_Error.
 
    Empty_Or_Error : constant Node_Id := Error;
    --  Since Empty and Error are the first two Node_Id values, the test for
@@ -422,11 +422,12 @@ package Types is
    -- Types for Nlists Package --
    ------------------------------
 
-   --  List_Id values are used to identify node lists in the tree. They are
-   --  subscripts into the Lists table declared in package Tree. Note that the
-   --  special value Error_List is a subscript in this table, but the value
-   --  No_List is *not* a valid subscript, and any attempt to apply list
-   --  operations to No_List will cause a (detected) error.
+   --  List_Id values are used to identify node lists stored in the tree, so
+   --  that each node can be on at most one such list (see package Nlists for
+   --  further details). Note that the special value Error_List is a subscript
+   --  in this table, but the value No_List is *not* a valid subscript, and any
+   --  attempt to apply list operations to No_List will cause a (detected)
+   --  error.
 
    type List_Id is range List_Low_Bound .. List_High_Bound;
    --  Type used to identify a node list
@@ -449,24 +450,23 @@ package Types is
    -- Types for Elists Package --
    ------------------------------
 
-   --  Element list Id values are used to identify element lists stored in the
-   --  tree (see package Atree for further details). They are formed by adding
-   --  a bias (Element_List_Bias) to subscript values in the same array that is
-   --  used for node list headers.
+   --  Element list Id values are used to identify element lists stored outside
+   --  of the tree, allowing nodes to be members of more than one such list
+   --  (see package Elists for further details).
 
    type Elist_Id is range Elist_Low_Bound .. Elist_High_Bound;
    --  Type used to identify an element list (Elist header table subscript)
 
    No_Elist : constant Elist_Id := Elist_Low_Bound;
-   --  Used to indicate absence of an element list. Note that this is not
-   --  an actual Elist header, so element list operations on this value
-   --  are not valid.
+   --  Used to indicate absence of an element list. Note that this is not an
+   --  actual Elist header, so element list operations on this value are not
+   --  valid.
 
    First_Elist_Id : constant Elist_Id := No_Elist + 1;
    --  Subscript of first allocated Elist header
 
-   --  Element Id values are used to identify individual elements of an
-   --  element list (see package Elists for further details).
+   --  Element Id values are used to identify individual elements of an element
+   --  list (see package Elists for further details).
 
    type Elmt_Id is range Elmt_Low_Bound .. Elmt_High_Bound;
    --  Type used to identify an element list
@@ -482,11 +482,12 @@ package Types is
    -------------------------------
 
    --  String_Id values are used to identify entries in the strings table. They
-   --  are subscripts into the strings table defined in package Strings.
+   --  are subscripts into the Strings table defined in package Stringt.
 
    --  Note that with only a few exceptions, which are clearly documented, the
    --  type String_Id should be regarded as a private type. In particular it is
    --  never appropriate to perform arithmetic operations using this type.
+   --  Doesn't this also apply to all other *_Id types???
 
    type String_Id is range Strings_Low_Bound .. Strings_High_Bound;
    --  Type used to identify entries in the strings table
@@ -554,7 +555,7 @@ package Types is
    type Unit_Number_Type is new Int;
    --  Unit number. The main source is unit 0, and subsidiary sources have
    --  non-zero numbers starting with 1. Unit numbers are used to index the
-   --  file table in Lib.
+   --  Units table in package Lib.
 
    Main_Unit : constant Unit_Number_Type := 0;
    --  Unit number value for main unit