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

--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--                             R E S T R I C T                              --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 1992-2008, 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.      --

--                                                                          --

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

--  This package deals with the implementation of the Restrictions pragma

with Namet;  use Namet;

with Rident; use Rident;

with Table;

with Types;  use Types;

with Uintp;  use Uintp;

package Restrict is

   Restrictions : Restrictions_Info := No_Restrictions;

   --  This variable records restrictions found in any units in the main

   --  extended unit, and in the case of restrictions checked for partition

   --  consistency, restrictions found in any with'ed units, parent specs

   --  etc., since we may as well check as much as we can at compile time.

   --  These variables should not be referenced directly by clients. Instead

   --  use Check_Restrictions to record a violation of a restriction, and

   --  Restriction_Active to test if a given restriction is active.

   Restrictions_Loc : array (All_Restrictions) of Source_Ptr :=

                       (others => No_Location);

   --  Locations of Restrictions pragmas for error message purposes.

   --  Valid only if corresponding entry in Restrictions is set. A value

   --  of No_Location is used for implicit restrictions set by another

   --  pragma, and a value of System_Location is used for restrictions

   --  set from package Standard by the processing in Targparm.

   Restriction_Profile_Name : array (All_Restrictions) of Profile_Name;

   --  Entries in this array are valid only if the corresponding restriction

   --  in Restrictions set. The value is the corresponding profile name if the

   --  restriction was set by a Profile or Profile_Warnings pragma. The value

   --  is No_Profile in all other cases.

   Main_Restrictions : Restrictions_Info := No_Restrictions;

   --  This variable records only restrictions found in any units of the

   --  main extended unit. These are the variables used for ali file output,

   --  since we want the binder to be able to accurately diagnose inter-unit

   --  restriction violations.

   Restriction_Warnings : Rident.Restriction_Flags;

   --  If one of these flags is set, then it means that violation of the

   --  corresponding restriction results only in a warning message, not

   --  in an error message, and the restriction is not otherwise enforced.

   --  Note that the flags in Restrictions are set to indicate that the

   --  restriction is set in this case, but Main_Restrictions is never

   --  set if Restriction_Warnings is set, so this does not look like a

   --  restriction to the binder.

   type Save_Cunit_Boolean_Restrictions is private;

   --  Type used for saving and restoring compilation unit restrictions.

   --  See Cunit_Boolean_Restrictions_[Save|Restore] subprograms.

   --  The following declarations establish a mapping between restriction

   --  identifiers, and the names of corresponding restriction library units.

   type Unit_Entry is record

      Res_Id : Restriction_Id;

      Filenm : String (1 .. 8);

   end record;

   Unit_Array : constant array (Positive range <>) of Unit_Entry := (

     (No_Asynchronous_Control,     "a-astaco"),

     (No_Calendar,                 "a-calend"),

     (No_Calendar,                 "calendar"),

     (No_Delay,                    "a-calend"),

     (No_Delay,                    "calendar"),

     (No_Dynamic_Priorities,       "a-dynpri"),

     (No_Finalization,             "a-finali"),

     (No_IO,                       "a-direio"),

     (No_IO,                       "directio"),

     (No_IO,                       "a-sequio"),

     (No_IO,                       "sequenio"),

     (No_IO,                       "a-ststio"),

     (No_IO,                       "a-textio"),

     (No_IO,                       "text_io "),

     (No_IO,                       "a-witeio"),

     (No_Task_Attributes_Package,  "a-tasatt"),

     (No_Unchecked_Conversion,     "a-unccon"),

     (No_Unchecked_Conversion,     "unchconv"),

     (No_Unchecked_Deallocation,   "a-uncdea"),

     (No_Unchecked_Deallocation,   "unchdeal"));

   --  The following map has True for all GNAT pragmas. It is used to

   --  implement pragma Restrictions (No_Implementation_Restrictions)

   --  (which is why this restriction itself is excluded from the list).

   Implementation_Restriction : array (All_Restrictions) of Boolean :=

     (Simple_Barriers                    => True,

      No_Asynchronous_Control            => True,

      No_Calendar                        => True,

      No_Dispatching_Calls               => True,

      No_Dynamic_Attachment              => True,

      No_Elaboration_Code                => True,

      No_Enumeration_Maps                => True,

      No_Entry_Calls_In_Elaboration_Code => True,

      No_Entry_Queue                     => True,

      No_Exception_Handlers              => True,

      No_Exception_Registration          => True,

      No_Implementation_Attributes       => True,

      No_Implementation_Pragmas          => True,

      No_Implicit_Conditionals           => True,

      No_Implicit_Dynamic_Code           => True,

      No_Implicit_Loops                  => True,

      No_Local_Protected_Objects         => True,

      No_Protected_Type_Allocators       => True,

      No_Relative_Delay                  => True,

      No_Requeue_Statements              => True,

      No_Secondary_Stack                 => True,

      No_Select_Statements               => True,

      No_Standard_Storage_Pools          => True,

      No_Streams                         => True,

      No_Task_Attributes_Package         => True,

      No_Task_Termination                => True,

      No_Unchecked_Conversion            => True,

      No_Unchecked_Deallocation          => True,

      No_Wide_Characters                 => True,

      Static_Priorities                  => True,

      Static_Storage_Size                => True,

      others                             => False);

   --  The following table records entries made by Restrictions pragmas

   --  that specify a parameter for No_Dependence. Each such pragma makes

   --  an entry in this table.

   --  Note: we have chosen to implement this restriction in the "syntactic"

   --  form, where we do not check that the named package is a language defined

   --  package, but instead we allow arbitrary package names. The discussion of

   --  this issue is not complete in the ARG, but the sense seems to be leaning

   --  in this direction, which makes more sense to us, since it is much more

   --  useful, and much easier to implement.

   type ND_Entry is record

      Unit : Node_Id;

      --  The unit parameter from the No_Dependence pragma

      Warn : Boolean;

      --  True if from Restriction_Warnings, False if from Restrictions

      Profile : Profile_Name;

      --  Set to name of profile from which No_Dependence entry came, or to

      --  No_Profile if a pragma Restriction set the No_Dependence entry.

   end record;

   package No_Dependence is new Table.Table (

     Table_Component_Type => ND_Entry,

     Table_Index_Type     => Int,

     Table_Low_Bound      => 0,

     Table_Initial        => 200,

     Table_Increment      => 200,

     Table_Name           => "Name_No_Dependence");

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

   -- Subprograms --

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

   function Abort_Allowed return Boolean;

   pragma Inline (Abort_Allowed);

   --  Tests to see if abort is allowed by the current restrictions settings.

   --  For abort to be allowed, either No_Abort_Statements must be False,

   --  or Max_Asynchronous_Select_Nesting must be non-zero.

   procedure Check_Compiler_Unit (N : Node_Id);

   --  If unit N is in a unit that has a pragma Compiler_Unit, then a message

   --  is posted on node N noting use of a construct that is not permitted in

   --  the compiler.

   procedure Check_Restricted_Unit (U : Unit_Name_Type; N : Node_Id);

   --  Checks if loading of unit U is prohibited by the setting of some

   --  restriction (e.g. No_IO restricts the loading of unit Ada.Text_IO).

   --  If a restriction exists post error message at the given node.

   procedure Check_Restriction

     (R : Restriction_Id;

      N : Node_Id;

      V : Uint := Uint_Minus_1);

   --  Checks that the given restriction is not set, and if it is set, an

   --  appropriate message is posted on the given node. Also records the

   --  violation in the appropriate internal arrays. Note that it is mandatory

   --  to always use this routine to check if a restriction is violated. Such

   --  checks must never be done directly by the caller, since otherwise

   --  violations in the absence of restrictions are not properly recorded. The

   --  value of V is relevant only for parameter restrictions, and in this case

   --  indicates the exact count for the violation. If the exact count is not

   --  known, V is left at its default of -1 which indicates an unknown count.

   procedure Check_Restriction_No_Dependence (U : Node_Id; Err : Node_Id);

   --  Called when a dependence on a unit is created (either implicitly, or by

   --  an explicit WITH clause). U is a node for the unit involved, and Err

   --  is the node to which an error will be attached if necessary.

   procedure Check_Elaboration_Code_Allowed (N : Node_Id);

   --  Tests to see if elaboration code is allowed by the current restrictions

   --  settings. This function is called by Gigi when it needs to define

   --  an elaboration routine. If elaboration code is not allowed, an error

   --  message is posted on the node given as argument.

   procedure Check_Implicit_Dynamic_Code_Allowed (N : Node_Id);

   --  Tests to see if dynamic code generation (dynamically generated

   --  trampolines, in particular) is allowed by the current restrictions

   --  settings. This function is called by Gigi when it needs to generate code

   --  that generates a trampoline. If not allowed, an error message is posted

   --  on the node given as argument.

   procedure Check_No_Implicit_Heap_Alloc (N : Node_Id);

   --  Equivalent to Check_Restriction (No_Implicit_Heap_Allocations, N).

   --  Provided for easy use by back end, which has to check this restriction.

   function Cunit_Boolean_Restrictions_Save

     return Save_Cunit_Boolean_Restrictions;

   --  This function saves the compilation unit restriction settings, and

   --  resets them to False. This is used e.g. when compiling a with'ed

   --  unit to avoid incorrectly propagating restrictions. Note that it

   --  would not be wrong to also save and reset the partition restrictions,

   --  since the binder would catch inconsistencies, but actually it is a

   --  good thing to acquire restrictions from with'ed units if they are

   --  required to be partition wide, because it allows the restriction

   --  violation message to be given at compile time instead of link time.

   procedure Cunit_Boolean_Restrictions_Restore

     (R : Save_Cunit_Boolean_Restrictions);

   --  This is the corresponding restore procedure to restore restrictions

   --  previously saved by Cunit_Boolean_Restrictions_Save.

   function Get_Restriction_Id

     (N : Name_Id) return Restriction_Id;

   --  Given an identifier name, determines if it is a valid restriction

   --  identifier, and if so returns the corresponding Restriction_Id

   --  value, otherwise returns Not_A_Restriction_Id.

   function No_Exception_Handlers_Set return Boolean;

   --  Test to see if current restrictions settings specify that no exception

   --  handlers are present. This function is called by Gigi when it needs to

   --  expand an AT END clean up identifier with no exception handler. True

   --  will be returned if the configurable run-time is activated, and either

   --  of the restrictions No_Exception_Handlers or No_Exception_Propagation is

   --  set. In the latter case, the source may contain handlers but they either

   --  get converted using the local goto transformation or deleted.

   function No_Exception_Propagation_Active return Boolean;

   --  Test to see if current restrictions settings specify that no

   --  exception propagation is activated.

   function Process_Restriction_Synonyms (N : Node_Id) return Name_Id;

   --  Id is a node whose Chars field contains the name of a restriction.

   --  If it is one of synonyms that we allow for historical purposes (for

   --  list see System.Rident), then the proper official name is returned.

   --  Otherwise the Chars field of the argument is returned unchanged.

   function Restriction_Active (R : All_Restrictions) return Boolean;

   pragma Inline (Restriction_Active);

   --  Determines if a given restriction is active. This call should only be

   --  used where the compiled code depends on whether the restriction is

   --  active. Always use Check_Restriction to record a violation. Note that

   --  this returns False if we only have a Restriction_Warnings set, since

   --  restriction warnings should never affect generated code.

   function Restricted_Profile return Boolean;

   --  Tests if set of restrictions corresponding to Profile (Restricted) is

   --  currently in effect (set by pragma Profile, or by an appropriate set

   --  of individual Restrictions pragmas). Returns True only if all the

   --  required restrictions are set.

   procedure Set_Profile_Restrictions

     (P    : Profile_Name;

      N    : Node_Id;

      Warn : Boolean);

   --  Sets the set of restrictions associated with the given profile name. N

   --  is the node of the construct to which error messages are to be attached

   --  as required. Warn is set True for the case of Profile_Warnings where the

   --  restrictions are set as warnings rather than legality requirements, and

   --  is also True for Profile if the Treat_Restrictions_As_Warnings flag is

   --  set. It is false for Profile if this flag is not set.

   procedure Set_Restriction

     (R : All_Boolean_Restrictions;

      N : Node_Id);

   --  N is a node (typically a pragma node) that has the effect of setting

   --  Boolean restriction R. The restriction is set in Restrictions, and

   --  also in Main_Restrictions if this is the main unit.

   procedure Set_Restriction

     (R : All_Parameter_Restrictions;

      N : Node_Id;

      V : Integer);

   --  Similar to the above, except that this is used for the case of a

   --  parameter restriction, and the corresponding value V is given.

   procedure Set_Restriction_No_Dependence

     (Unit    : Node_Id;

      Warn    : Boolean;

      Profile : Profile_Name := No_Profile);

   --  Sets given No_Dependence restriction in table if not there already.

   --  Warn is True if from Restriction_Warnings, or for Restrictions if flag

   --  Treat_Restrictions_As_Warnings is set. False if from Restrictions and

   --  this flag is not set. Profile is set to a non-default value if the

   --  No_Dependence restriction comes from a Profile pragma.

   function Tasking_Allowed return Boolean;

   pragma Inline (Tasking_Allowed);

   --  Tests if tasking operations are allowed by the current restrictions

   --  settings. For tasking to be allowed Max_Tasks must be non-zero.

private

   type Save_Cunit_Boolean_Restrictions is

     array (Cunit_Boolean_Restrictions) of Boolean;

   --  Type used for saving and restoring compilation unit restrictions.

   --  See Compilation_Unit_Restrictions_[Save|Restore] subprograms.

end Restrict;