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------------------------------------------------------------------------------

--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--                             L I B . L O A D                              --

--                                                                          --

--                                 B o d y                                  --

--                                                                          --

--          Copyright (C) 1992-2012, 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- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --

-- for  more details.  You should have  received  a copy of the GNU General --

-- Public License  distributed with GNAT; see file COPYING3.  If not, go to --

-- http://www.gnu.org/licenses for a complete copy of the license.          --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

------------------------------------------------------------------------------

with Atree;    use Atree;

with Debug;    use Debug;

with Einfo;    use Einfo;

with Errout;   use Errout;

with Fname;    use Fname;

with Fname.UF; use Fname.UF;

with Nlists;   use Nlists;

with Nmake;    use Nmake;

with Opt;      use Opt;

with Osint;    use Osint;

with Osint.C;  use Osint.C;

with Output;   use Output;

with Par;

with Restrict; use Restrict;

with Scn;      use Scn;

with Sinfo;    use Sinfo;

with Sinput;   use Sinput;

with Sinput.L; use Sinput.L;

with Stand;    use Stand;

with Tbuild;   use Tbuild;

with Uname;    use Uname;

package body Lib.Load is

   -----------------------

   -- Local Subprograms --

   -----------------------

   function From_Limited_With_Chain return Boolean;

   --  Check whether a possible circular dependence includes units that

   --  have been loaded through limited_with clauses, in which case there

   --  is no real circularity.

   function Spec_Is_Irrelevant

     (Spec_Unit : Unit_Number_Type;

      Body_Unit : Unit_Number_Type) return Boolean;

   --  The Spec_Unit and Body_Unit parameters are the unit numbers of the

   --  spec file that corresponds to the main unit which is a body. This

   --  function determines if the spec file is irrelevant and will be

   --  overridden by the body as described in RM 10.1.4(4). See description

   --  in "Special Handling of Subprogram Bodies" for further details.

   procedure Write_Dependency_Chain;

   --  This procedure is used to generate error message info lines that

   --  trace the current dependency chain when a load error occurs.

   ------------------------------

   -- Change_Main_Unit_To_Spec --

   ------------------------------

   procedure Change_Main_Unit_To_Spec is

      U : Unit_Record renames Units.Table (Main_Unit);

      N : File_Name_Type;

      X : Source_File_Index;

   begin

      --  Get name of unit body

      Get_Name_String (U.Unit_File_Name);

      --  Note: for the following we should really generalize and consult the

      --  file name pattern data, but for now we just deal with the common

      --  naming cases, which is probably good enough in practice ???

      --  Change .adb to .ads

      if Name_Len >= 5

        and then Name_Buffer (Name_Len - 3 .. Name_Len) = ".adb"

      then

         Name_Buffer (Name_Len) := 's';

      --  Change .2.ada to .1.ada (Rational convention)

      elsif Name_Len >= 7

        and then Name_Buffer (Name_Len - 5 .. Name_Len) = ".2.ada"

      then

         Name_Buffer (Name_Len - 4) := '1';

      --  Change .ada to _.ada (DEC convention)

      elsif Name_Len >= 5

        and then Name_Buffer (Name_Len - 3 .. Name_Len) = ".ada"

      then

         Name_Buffer (Name_Len - 3 .. Name_Len + 1) := "_.ada";

         Name_Len := Name_Len + 1;

      --  No match, don't make the change

      else

         return;

      end if;

      --  Try loading the spec

      N := Name_Find;

      X := Load_Source_File (N);

      --  No change if we did not find the spec

      if X = No_Source_File then

         return;

      end if;

      --  Otherwise modify Main_Unit entry to point to spec

      U.Unit_File_Name := N;

      U.Source_Index := X;

   end Change_Main_Unit_To_Spec;

   -------------------------------

   -- Create_Dummy_Package_Unit --

   -------------------------------

   function Create_Dummy_Package_Unit

     (With_Node : Node_Id;

      Spec_Name : Unit_Name_Type) return Unit_Number_Type

   is

      Unum         : Unit_Number_Type;

      Cunit_Entity : Entity_Id;

      Cunit        : Node_Id;

      Du_Name      : Node_Or_Entity_Id;

      End_Lab      : Node_Id;

      Save_CS      : constant Boolean := Get_Comes_From_Source_Default;

   begin

      --  The created dummy package unit does not come from source

      Set_Comes_From_Source_Default (False);

      --  Normal package

      if Nkind (Name (With_Node)) = N_Identifier then

         Cunit_Entity :=

           Make_Defining_Identifier (No_Location,

             Chars => Chars (Name (With_Node)));

         Du_Name := Cunit_Entity;

         End_Lab := New_Occurrence_Of (Cunit_Entity, No_Location);

      --  Child package

      else

         Cunit_Entity :=

           Make_Defining_Identifier (No_Location,

             Chars => Chars (Selector_Name (Name (With_Node))));

         Du_Name :=

           Make_Defining_Program_Unit_Name (No_Location,

             Name => Copy_Separate_Tree (Prefix (Name (With_Node))),

             Defining_Identifier => Cunit_Entity);

         Set_Is_Child_Unit (Cunit_Entity);

         End_Lab :=

           Make_Designator (No_Location,

             Name => Copy_Separate_Tree (Prefix (Name (With_Node))),

             Identifier => New_Occurrence_Of (Cunit_Entity, No_Location));

      end if;

      Set_Scope (Cunit_Entity, Standard_Standard);

      Cunit :=

        Make_Compilation_Unit (No_Location,

          Context_Items => Empty_List,

          Unit =>

            Make_Package_Declaration (No_Location,

              Specification =>

                Make_Package_Specification (No_Location,

                  Defining_Unit_Name   => Du_Name,

                  Visible_Declarations => Empty_List,

                  End_Label            => End_Lab)),

          Aux_Decls_Node =>

            Make_Compilation_Unit_Aux (No_Location));

      --  Mark the dummy package as analyzed to prevent analysis of this

      --  (non-existent) unit in -gnatQ mode because at the moment the

      --  structure and attributes of this dummy package does not allow

      --  a normal analysis of this unit

      Set_Analyzed (Cunit);

      Units.Increment_Last;

      Unum := Units.Last;

      Units.Table (Unum) := (

        Cunit            => Cunit,

        Cunit_Entity     => Cunit_Entity,

        Dependency_Num   => 0,

        Dynamic_Elab     => False,

        Error_Location   => Sloc (With_Node),

        Expected_Unit    => Spec_Name,

        Fatal_Error      => True,

        Generate_Code    => False,

        Has_Allocator    => False,

        Has_RACW         => False,

        Is_Compiler_Unit => False,

        Ident_String     => Empty,

        Loading          => False,

        Main_Priority    => Default_Main_Priority,

        Main_CPU         => Default_Main_CPU,

        Munit_Index      => 0,

        Serial_Number    => 0,

        Source_Index     => No_Source_File,

        Unit_File_Name   => Get_File_Name (Spec_Name, Subunit => False),

        Unit_Name        => Spec_Name,

        Version          => 0,

        OA_Setting       => 'O');

      Set_Comes_From_Source_Default (Save_CS);

      Set_Error_Posted (Cunit_Entity);

      Set_Error_Posted (Cunit);

      return Unum;

   end Create_Dummy_Package_Unit;

   -----------------------------

   -- From_Limited_With_Chain --

   -----------------------------

   function From_Limited_With_Chain return Boolean is

      Curr_Num : constant Unit_Number_Type :=

                   Load_Stack.Table (Load_Stack.Last).Unit_Number;

   begin

      --  True if the current load operation is through a limited_with clause

      --  and we are not within a loop of regular with_clauses.

      for U in reverse Load_Stack.First .. Load_Stack.Last - 1 loop

         if Load_Stack.Table (U).Unit_Number = Curr_Num then

            return False;

         elsif Present (Load_Stack.Table (U).With_Node)

           and then Limited_Present (Load_Stack.Table (U).With_Node)

         then

            return True;

         end if;

      end loop;

      return False;

   end From_Limited_With_Chain;

   ----------------

   -- Initialize --

   ----------------

   procedure Initialize is

   begin

      Units.Init;

      Load_Stack.Init;

   end Initialize;

   ------------------------

   -- Initialize_Version --

   ------------------------

   procedure Initialize_Version (U : Unit_Number_Type) is

   begin

      Units.Table (U).Version := Source_Checksum (Source_Index (U));

   end Initialize_Version;

   ----------------------

   -- Load_Main_Source --

   ----------------------

   procedure Load_Main_Source is

      Fname   : File_Name_Type;

      Version : Word := 0;

   begin

      Load_Stack.Increment_Last;

      Load_Stack.Table (Load_Stack.Last) := (Main_Unit, Empty);

      --  Initialize unit table entry for Main_Unit. Note that we don't know

      --  the unit name yet, that gets filled in when the parser parses the

      --  main unit, at which time a check is made that it matches the main

      --  file name, and then the Unit_Name field is set. The Cunit and

      --  Cunit_Entity fields also get filled in later by the parser.

      Units.Increment_Last;

      Fname := Next_Main_Source;

      Units.Table (Main_Unit).Unit_File_Name := Fname;

      if Fname /= No_File then

         Main_Source_File := Load_Source_File (Fname);

         Current_Error_Source_File := Main_Source_File;

         if Main_Source_File /= No_Source_File then

            Version := Source_Checksum (Main_Source_File);

         end if;

         Units.Table (Main_Unit) := (

           Cunit            => Empty,

           Cunit_Entity     => Empty,

           Dependency_Num   => 0,

           Dynamic_Elab     => False,

           Error_Location   => No_Location,

           Expected_Unit    => No_Unit_Name,

           Fatal_Error      => False,

           Generate_Code    => False,

           Has_Allocator    => False,

           Has_RACW         => False,

           Is_Compiler_Unit => False,

           Ident_String     => Empty,

           Loading          => True,

           Main_Priority    => Default_Main_Priority,

           Main_CPU         => Default_Main_CPU,

           Munit_Index      => 0,

           Serial_Number    => 0,

           Source_Index     => Main_Source_File,

           Unit_File_Name   => Fname,

           Unit_Name        => No_Unit_Name,

           Version          => Version,

           OA_Setting       => 'O');

      end if;

   end Load_Main_Source;

   ---------------

   -- Load_Unit --

   ---------------

   function Load_Unit

     (Load_Name         : Unit_Name_Type;

      Required          : Boolean;

      Error_Node        : Node_Id;

      Subunit           : Boolean;

      Corr_Body         : Unit_Number_Type := No_Unit;

      Renamings         : Boolean          := False;

      With_Node         : Node_Id          := Empty;

      PMES              : Boolean          := False) return Unit_Number_Type

   is

      Calling_Unit : Unit_Number_Type;

      Uname_Actual : Unit_Name_Type;

      Unum         : Unit_Number_Type;

      Unump        : Unit_Number_Type;

      Fname        : File_Name_Type;

      Src_Ind      : Source_File_Index;

      Save_PMES    : constant Boolean := Parsing_Main_Extended_Source;

      Save_Cunit_Restrictions : constant Save_Cunit_Boolean_Restrictions :=

                                  Cunit_Boolean_Restrictions_Save;

      --  Save current restrictions for restore at end

   begin

      Parsing_Main_Extended_Source := PMES;

      --  Initialize restrictions to config restrictions for unit to load if

      --  it is part of the main extended source, otherwise reset them.

      --  Note: it's a bit odd but PMES is False for subunits, which is why

      --  we have the OR here. Should be investigated some time???

      if PMES or Subunit then

         Restore_Config_Cunit_Boolean_Restrictions;

      else

         Reset_Cunit_Boolean_Restrictions;

      end if;

      --  If renamings are allowed and we have a child unit name, then we

      --  must first load the parent to deal with finding the real name.

      --  Retain the with_clause that names the child, so that if it is

      --  limited, the parent is loaded under the same condition.

      if Renamings and then Is_Child_Name (Load_Name) then

         Unump :=

           Load_Unit

             (Load_Name  => Get_Parent_Spec_Name (Load_Name),

              Required   => Required,

              Subunit    => False,

              Renamings  => True,

              Error_Node => Error_Node,

              With_Node  => With_Node);

         if Unump = No_Unit then

            Parsing_Main_Extended_Source := Save_PMES;

            return No_Unit;

         end if;

         --  If parent is a renaming, then we use the renamed package as

         --  the actual parent for the subsequent load operation.

         if Nkind (Unit (Cunit (Unump))) = N_Package_Renaming_Declaration then

            Uname_Actual :=

              New_Child

                (Load_Name, Get_Unit_Name (Name (Unit (Cunit (Unump)))));

            --  If the load is for a with_clause, for visibility purposes both

            --  the renamed entity and renaming one must be available in the

            --  current unit: the renamed one in order to retrieve the child

            --  unit, and the original one because it may be used as a prefix

            --  in the body of the current unit. We add an explicit with_clause

            --  for the original parent so that the renaming declaration is

            --  properly loaded and analyzed.

            if Present (With_Node) then

               Insert_After (With_Node,

                 Make_With_Clause (Sloc (With_Node),

                   Name => Copy_Separate_Tree (Prefix (Name (With_Node)))));

            end if;

            --  Save the renaming entity, to establish its visibility when

            --  installing the context. The implicit with is on this entity,

            --  not on the package it renames. This is somewhat redundant given

            --  the with_clause just created, but it simplifies subsequent

            --  expansion of the current with_clause. Optimizable ???

            if Nkind (Error_Node) = N_With_Clause

              and then Nkind (Name (Error_Node)) = N_Selected_Component

            then

               declare

                  Par : Node_Id := Name (Error_Node);

               begin

                  while Nkind (Par) = N_Selected_Component

                    and then Chars (Selector_Name (Par)) /=

                             Chars (Cunit_Entity (Unump))

                  loop

                     Par := Prefix (Par);

                  end loop;

                  --  Case of some intermediate parent is a renaming

                  if Nkind (Par) = N_Selected_Component then

                     Set_Entity (Selector_Name (Par), Cunit_Entity (Unump));

                  --  Case where the ultimate parent is a renaming

                  else

                     Set_Entity (Par, Cunit_Entity (Unump));

                  end if;

               end;

            end if;

         --  If the parent is not a renaming, then get its name (this may

         --  be different from the parent spec name obtained above because

         --  of renamings higher up in the hierarchy).

         else

            Uname_Actual := New_Child (Load_Name, Unit_Name (Unump));

         end if;

      --  Here if unit to be loaded is not a child unit

      else

         Uname_Actual := Load_Name;

      end if;

      Fname := Get_File_Name (Uname_Actual, Subunit);

      if Debug_Flag_L then

         Write_Eol;

         Write_Str ("*** Load request for unit: ");

         Write_Unit_Name (Load_Name);

         if Required then

            Write_Str (" (Required = True)");

         else

            Write_Str (" (Required = False)");

         end if;

         Write_Eol;

         if Uname_Actual /= Load_Name then

            Write_Str ("*** Actual unit loaded: ");

            Write_Unit_Name (Uname_Actual);

         end if;

      end if;

      --  Capture error location if it is for the main unit. The idea is to

      --  post errors on the main unit location, not the most recent unit.

      --  Note: Unit_Name (Main_Unit) is not set if we are parsing gnat.adc.

      if Present (Error_Node)

        and then Unit_Name (Main_Unit) /= No_Unit_Name

      then

         --  It seems like In_Extended_Main_Source_Unit (Error_Node) would

         --  do the trick here, but that's wrong, it is much too early to

         --  call this routine. We are still in the parser, and the required

         --  semantic information is not established yet. So we base the

         --  judgment on unit names.

         Get_External_Unit_Name_String (Unit_Name (Main_Unit));

         declare

            Main_Unit_Name : constant String := Name_Buffer (1 .. Name_Len);

         begin

            Get_External_Unit_Name_String

              (Unit_Name (Get_Source_Unit (Error_Node)));

            --  If the two names are identical, then for sure we are part

            --  of the extended main unit

            if Main_Unit_Name = Name_Buffer (1 .. Name_Len) then

               Load_Msg_Sloc := Sloc (Error_Node);

            --  If the load is called from a with_type clause, the error

            --  node is correct.

            --  Otherwise, check for the subunit case, and if so, consider

            --  we have a match if one name is a prefix of the other name.

            else

               if Nkind (Unit (Cunit (Main_Unit))) = N_Subunit

                    or else

                  Nkind (Unit (Cunit (Get_Source_Unit (Error_Node)))) =

                                                                N_Subunit

               then

                  Name_Len := Integer'Min (Name_Len, Main_Unit_Name'Length);

                  if Name_Buffer (1 .. Name_Len)

                        =

                     Main_Unit_Name (1 .. Name_Len)

                  then

                     Load_Msg_Sloc := Sloc (Error_Node);

                  end if;

               end if;

            end if;

         end;

      end if;

      --  If we are generating error messages, then capture calling unit

      if Present (Error_Node) then

         Calling_Unit := Get_Source_Unit (Error_Node);

      else

         Calling_Unit := No_Unit;

      end if;

      --  See if we already have an entry for this unit

      Unum := Main_Unit;

      while Unum <= Units.Last loop

         exit when Uname_Actual = Units.Table (Unum).Unit_Name;

         Unum := Unum + 1;

      end loop;

      --  Whether or not the entry was found, Unum is now the right value,

      --  since it is one more than Units.Last (i.e. the index of the new

      --  entry we will create) in the not found case.

      --  A special check is necessary in the unit not found case. If the unit

      --  is not found, but the file in which it lives has already been loaded,

      --  then we have the problem that the file does not contain the unit that

      --  is needed. We simply treat this as a file not found condition.

      --  We skip this test in multiple unit per file mode since in this

      --  case we can have multiple units from the same source file.

      if Unum > Units.Last and then Get_Unit_Index (Uname_Actual) = 0 then

         for J in Units.First .. Units.Last loop

            if Fname = Units.Table (J).Unit_File_Name then

               if Debug_Flag_L then

                  Write_Str ("  file does not contain unit, Unit_Number = ");

                  Write_Int (Int (Unum));

                  Write_Eol;

                  Write_Eol;

               end if;

               if Present (Error_Node) then

                  if Is_Predefined_File_Name (Fname) then

                     Error_Msg_Unit_1 := Uname_Actual;

                     Error_Msg

                       ("$$ is not a language defined unit", Load_Msg_Sloc);

                  else

                     Error_Msg_File_1 := Fname;

                     Error_Msg_Unit_1 := Uname_Actual;

                     Error_Msg ("File{ does not contain unit$", Load_Msg_Sloc);

                  end if;

                  Write_Dependency_Chain;

                  Unum := No_Unit;

                  goto Done;

               else

                  Unum := No_Unit;

                  goto Done;

               end if;

            end if;

         end loop;

      end if;

      --  If we are proceeding with load, then make load stack entry,

      --  and indicate the kind of with_clause responsible for the load.

      Load_Stack.Increment_Last;

      Load_Stack.Table (Load_Stack.Last) := (Unum, With_Node);

      --  Case of entry already in table

      if Unum <= Units.Last then

         --  Here is where we check for a circular dependency, which is

         --  an attempt to load a unit which is currently in the process

         --  of being loaded. We do *not* care about a circular chain that

         --  leads back to a body, because this kind of circular dependence

         --  legitimately occurs (e.g. two package bodies that contain

         --  inlined subprogram referenced by the other).

         --  Ada 2005 (AI-50217): We also ignore limited_with clauses, because

         --  their purpose is precisely to create legal circular structures.

         if Loading (Unum)

           and then (Is_Spec_Name (Units.Table (Unum).Unit_Name)

                       or else Acts_As_Spec (Units.Table (Unum).Cunit))

           and then (Nkind (Error_Node) /= N_With_Clause

                       or else not Limited_Present (Error_Node))

           and then not From_Limited_With_Chain

         then

            if Debug_Flag_L then

               Write_Str ("  circular dependency encountered");

               Write_Eol;

            end if;

            if Present (Error_Node) then

               Error_Msg ("circular unit dependency", Load_Msg_Sloc);

               Write_Dependency_Chain;

            else

               Load_Stack.Decrement_Last;

            end if;

            Unum := No_Unit;

            goto Done;

         end if;

         if Debug_Flag_L then

            Write_Str ("  unit already in file table, Unit_Number = ");

            Write_Int (Int (Unum));

            Write_Eol;

         end if;

         Load_Stack.Decrement_Last;

         goto Done;

      --  Unit is not already in table, so try to open the file

      else

         if Debug_Flag_L then

            Write_Str ("  attempt unit load, Unit_Number = ");

            Write_Int (Int (Unum));

            Write_Eol;

         end if;

         Src_Ind := Load_Source_File (Fname);

         --  Make a partial entry in the file table, used even in the file not

         --  found case to print the dependency chain including the last entry

         Units.Increment_Last;

         Units.Table (Unum).Unit_Name := Uname_Actual;

         --  File was found

         if Src_Ind /= No_Source_File then

            Units.Table (Unum) := (

              Cunit            => Empty,

              Cunit_Entity     => Empty,

              Dependency_Num   => 0,

              Dynamic_Elab     => False,

              Error_Location   => Sloc (Error_Node),

              Expected_Unit    => Uname_Actual,

              Fatal_Error      => False,

              Generate_Code    => False,

              Has_Allocator    => False,

              Has_RACW         => False,

              Is_Compiler_Unit => False,

              Ident_String     => Empty,

              Loading          => True,

              Main_Priority    => Default_Main_Priority,

              Main_CPU         => Default_Main_CPU,

              Munit_Index      => 0,

              Serial_Number    => 0,

              Source_Index     => Src_Ind,

              Unit_File_Name   => Fname,

              Unit_Name        => Uname_Actual,

              Version          => Source_Checksum (Src_Ind),

              OA_Setting       => 'O');

            --  Parse the new unit

            declare

               Save_Index : constant Nat     := Multiple_Unit_Index;

               Save_PMES  : constant Boolean := Parsing_Main_Extended_Source;

            begin

               Multiple_Unit_Index := Get_Unit_Index (Uname_Actual);

               Units.Table (Unum).Munit_Index := Multiple_Unit_Index;

               Initialize_Scanner (Unum, Source_Index (Unum));

               if Calling_Unit = Main_Unit and then Subunit then

                  Parsing_Main_Extended_Source := True;

               end if;

               Discard_List (Par (Configuration_Pragmas => False));

               Parsing_Main_Extended_Source := Save_PMES;

               Multiple_Unit_Index := Save_Index;

               Set_Loading (Unum, False);

            end;

            --  If spec is irrelevant, then post errors and quit

            if Corr_Body /= No_Unit

              and then Spec_Is_Irrelevant (Unum, Corr_Body)

            then

               Error_Msg_File_1 := Unit_File_Name (Corr_Body);

               Error_Msg

                 ("cannot compile subprogram in file {!", Load_Msg_Sloc);

               Error_Msg_File_1 := Unit_File_Name (Unum);

               Error_Msg

                 ("\incorrect spec in file { must be removed first!",

                  Load_Msg_Sloc);

               Unum := No_Unit;

               goto Done;

            end if;

            --  If loaded unit had a fatal error, then caller inherits it!

            if Units.Table (Unum).Fatal_Error

              and then Present (Error_Node)

            then

               Units.Table (Calling_Unit).Fatal_Error := True;

            end if;

            --  Remove load stack entry and return the entry in the file table

            Load_Stack.Decrement_Last;

            --  All done, return unit number

            goto Done;

         --  Case of file not found

         else

            if Debug_Flag_L then

               Write_Str ("  file was not found, load failed");

               Write_Eol;

            end if;

            --  Generate message if unit required

            if Required and then Present (Error_Node) then

               if Is_Predefined_File_Name (Fname) then

                  --  This is a predefined library unit which is not present

                  --  in the run time. If a predefined unit is not available

                  --  it may very likely be the case that there is also pragma

                  --  Restriction forbidding its usage. This is typically the

                  --  case when building a configurable run time, where the

                  --  usage of certain run-time units is restricted by means

                  --  of both the corresponding pragma Restriction (such as

                  --  No_Calendar), and by not including the unit. Hence, we

                  --  check whether this predefined unit is forbidden, so that

                  --  the message about the restriction violation is generated,

                  --  if needed.

                  Check_Restricted_Unit (Load_Name, Error_Node);

                  Error_Msg_Unit_1 := Uname_Actual;

                  Error_Msg -- CODEFIX

                    ("$$ is not a predefined library unit", Load_Msg_Sloc);

               else

                  Error_Msg_File_1 := Fname;

                  Error_Msg ("file{ not found", Load_Msg_Sloc);

               end if;

               Write_Dependency_Chain;

               --  Remove unit from stack, to avoid cascaded errors on

               --  subsequent missing files.