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

--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--                    S Y S T E M . S O F T _ L I N K S                     --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 1992-2011, 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.                                     --

--                                                                          --

-- As a special exception under Section 7 of GPL version 3, you are granted --

-- additional permissions described in the GCC Runtime Library Exception,   --

-- version 3.1, as published by the Free Software Foundation.               --

--                                                                          --

-- You should have received a copy of the GNU General Public License and    --

-- a copy of the GCC Runtime Library Exception along with this program;     --

-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --

-- <http://www.gnu.org/licenses/>.                                          --

--                                                                          --

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

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

--                                                                          --

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

--  This package contains a set of subprogram access variables that access

--  some low-level primitives that are different depending whether tasking is

--  involved or not (e.g. the Get/Set_Jmpbuf_Address that needs to provide a

--  different value for each task). To avoid dragging in the tasking runtimes

--  all the time, we use a system of soft links where the links are

--  initialized to non-tasking versions, and then if the tasking support is

--  initialized, they are set to the real tasking versions.

pragma Compiler_Unit;

with Ada.Exceptions;

with System.Stack_Checking;

package System.Soft_Links is

   pragma Preelaborate_05;

   subtype EOA is Ada.Exceptions.Exception_Occurrence_Access;

   subtype EO is Ada.Exceptions.Exception_Occurrence;

   function Current_Target_Exception return EO;

   pragma Import

     (Ada, Current_Target_Exception, "__gnat_current_target_exception");

   --  Import this subprogram from the private part of Ada.Exceptions

   --  First we have the access subprogram types used to establish the links.

   --  The approach is to establish variables containing access subprogram

   --  values, which by default point to dummy no tasking versions of routines.

   type No_Param_Proc     is access procedure;

   pragma Favor_Top_Level (No_Param_Proc);

   pragma Suppress_Initialization (No_Param_Proc);

   --  Some uninitialized objects of that type are initialized by the Binder

   --  so it is important that such objects are not reset to null during

   --  elaboration.

   type Addr_Param_Proc   is access procedure (Addr : Address);

   pragma Favor_Top_Level (Addr_Param_Proc);

   type EO_Param_Proc     is access procedure (Excep : EO);

   pragma Favor_Top_Level (EO_Param_Proc);

   type Get_Address_Call  is access function return Address;

   pragma Favor_Top_Level (Get_Address_Call);

   type Set_Address_Call  is access procedure (Addr : Address);

   pragma Favor_Top_Level (Set_Address_Call);

   type Set_Address_Call2 is access procedure

     (Self_ID : Address; Addr : Address);

   pragma Favor_Top_Level (Set_Address_Call2);

   type Get_Integer_Call  is access function return Integer;

   pragma Favor_Top_Level (Get_Integer_Call);

   type Set_Integer_Call  is access procedure (Len : Integer);

   pragma Favor_Top_Level (Set_Integer_Call);

   type Get_EOA_Call      is access function return EOA;

   pragma Favor_Top_Level (Get_EOA_Call);

   type Set_EOA_Call      is access procedure (Excep : EOA);

   pragma Favor_Top_Level (Set_EOA_Call);

   type Set_EO_Call       is access procedure (Excep : EO);

   pragma Favor_Top_Level (Set_EO_Call);

   type Special_EO_Call   is access

     procedure (Excep : EO := Current_Target_Exception);

   pragma Favor_Top_Level (Special_EO_Call);

   type Timed_Delay_Call  is access

     procedure (Time : Duration; Mode : Integer);

   pragma Favor_Top_Level (Timed_Delay_Call);

   type Get_Stack_Access_Call is access

     function return Stack_Checking.Stack_Access;

   pragma Favor_Top_Level (Get_Stack_Access_Call);

   type Task_Name_Call is access

     function return String;

   pragma Favor_Top_Level (Task_Name_Call);

   --  Suppress checks on all these types, since we know the corresponding

   --  values can never be null (the soft links are always initialized).

   pragma Suppress (Access_Check, No_Param_Proc);

   pragma Suppress (Access_Check, Addr_Param_Proc);

   pragma Suppress (Access_Check, EO_Param_Proc);

   pragma Suppress (Access_Check, Get_Address_Call);

   pragma Suppress (Access_Check, Set_Address_Call);

   pragma Suppress (Access_Check, Set_Address_Call2);

   pragma Suppress (Access_Check, Get_Integer_Call);

   pragma Suppress (Access_Check, Set_Integer_Call);

   pragma Suppress (Access_Check, Get_EOA_Call);

   pragma Suppress (Access_Check, Set_EOA_Call);

   pragma Suppress (Access_Check, Timed_Delay_Call);

   pragma Suppress (Access_Check, Get_Stack_Access_Call);

   pragma Suppress (Access_Check, Task_Name_Call);

   --  The following one is not related to tasking/no-tasking but to the

   --  traceback decorators for exceptions.

   type Traceback_Decorator_Wrapper_Call is access

     function (Traceback : System.Address;

               Len       : Natural)

               return      String;

   pragma Favor_Top_Level (Traceback_Decorator_Wrapper_Call);

   --  Declarations for the no tasking versions of the required routines

   procedure Abort_Defer_NT;

   --  Defer task abort (non-tasking case, does nothing)

   procedure Abort_Undefer_NT;

   --  Undefer task abort (non-tasking case, does nothing)

   procedure Abort_Handler_NT;

   --  Handle task abort (non-tasking case, does nothing). Currently, only VMS

   --  uses this.

   procedure Update_Exception_NT (X : EO := Current_Target_Exception);

   --  Handle exception setting. This routine is provided for targets that

   --  have built-in exception handling such as the Java Virtual Machine.

   --  Currently, only JGNAT uses this. See 4jexcept.ads for an explanation on

   --  how this routine is used.

   function Check_Abort_Status_NT return Integer;

   --  Returns Boolean'Pos (True) iff abort signal should raise

   --  Standard'Abort_Signal.

   procedure Task_Lock_NT;

   --  Lock out other tasks (non-tasking case, does nothing)

   procedure Task_Unlock_NT;

   --  Release lock set by Task_Lock (non-tasking case, does nothing)

   procedure Task_Termination_NT (Excep : EO);

   --  Handle task termination routines for the environment task (non-tasking

   --  case, does nothing).

   procedure Adafinal_NT;

   --  Shuts down the runtime system (non-tasking case)

   Abort_Defer : No_Param_Proc := Abort_Defer_NT'Access;

   pragma Suppress (Access_Check, Abort_Defer);

   --  Defer task abort (task/non-task case as appropriate)

   Abort_Undefer : No_Param_Proc := Abort_Undefer_NT'Access;

   pragma Suppress (Access_Check, Abort_Undefer);

   --  Undefer task abort (task/non-task case as appropriate)

   Abort_Handler : No_Param_Proc := Abort_Handler_NT'Access;

   --  Handle task abort (task/non-task case as appropriate)

   Update_Exception : Special_EO_Call := Update_Exception_NT'Access;

   --  Handle exception setting and tasking polling when appropriate

   Check_Abort_Status : Get_Integer_Call := Check_Abort_Status_NT'Access;

   --  Called when Abort_Signal is delivered to the process.  Checks to

   --  see if signal should result in raising Standard'Abort_Signal.

   Lock_Task : No_Param_Proc := Task_Lock_NT'Access;

   --  Locks out other tasks. Preceding a section of code by Task_Lock and

   --  following it by Task_Unlock creates a critical region. This is used

   --  for ensuring that a region of non-tasking code (such as code used to

   --  allocate memory) is tasking safe. Note that it is valid for calls to

   --  Task_Lock/Task_Unlock to be nested, and this must work properly, i.e.

   --  only the corresponding outer level Task_Unlock will actually unlock.

   --  This routine also prevents against asynchronous aborts (abort is

   --  deferred).

   Unlock_Task : No_Param_Proc := Task_Unlock_NT'Access;

   --  Releases lock previously set by call to Lock_Task. In the nested case,

   --  all nested locks must be released before other tasks competing for the

   --  tasking lock are released.

   --

   --  In the non nested case, this routine terminates the protection against

   --  asynchronous aborts introduced by Lock_Task (unless abort was already

   --  deferred before the call to Lock_Task (e.g in a protected procedures).

   --

   --  Note: the recommended protocol for using Lock_Task and Unlock_Task

   --  is as follows:

   --

   --    Locked_Processing : begin

   --       System.Soft_Links.Lock_Task.all;

   --       ...

   --       System.Soft_Links.Unlock_Task.all;

   --

   --    exception

   --       when others =>

   --          System.Soft_Links.Unlock_Task.all;

   --          raise;

   --    end Locked_Processing;

   --

   --  This ensures that the lock is not left set if an exception is raised

   --  explicitly or implicitly during the critical locked region.

   Task_Termination_Handler : EO_Param_Proc := Task_Termination_NT'Access;

   --  Handle task termination routines (task/non-task case as appropriate)

   Finalize_Library_Objects : No_Param_Proc;

   pragma Export (C, Finalize_Library_Objects,

                  "__gnat_finalize_library_objects");

   --  Will be initialized by the binder

   Adafinal : No_Param_Proc := Adafinal_NT'Access;

   --  Performs the finalization of the Ada Runtime

   function  Get_Jmpbuf_Address_NT return  Address;

   procedure Set_Jmpbuf_Address_NT (Addr : Address);

   Get_Jmpbuf_Address : Get_Address_Call := Get_Jmpbuf_Address_NT'Access;

   Set_Jmpbuf_Address : Set_Address_Call := Set_Jmpbuf_Address_NT'Access;

   function  Get_Sec_Stack_Addr_NT return  Address;

   procedure Set_Sec_Stack_Addr_NT (Addr : Address);

   Get_Sec_Stack_Addr : Get_Address_Call := Get_Sec_Stack_Addr_NT'Access;

   Set_Sec_Stack_Addr : Set_Address_Call := Set_Sec_Stack_Addr_NT'Access;

   function Get_Current_Excep_NT return EOA;

   Get_Current_Excep : Get_EOA_Call := Get_Current_Excep_NT'Access;

   function Get_Stack_Info_NT return Stack_Checking.Stack_Access;

   Get_Stack_Info : Get_Stack_Access_Call := Get_Stack_Info_NT'Access;

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

   -- Master_Id Soft-Links --

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

   --  Soft-Links are used for procedures that manipulate Master_Ids because

   --  a Master_Id must be generated for access to limited class-wide types,

   --  whose root may be extended with task components.

   function Current_Master_NT return Integer;

   procedure Enter_Master_NT;

   procedure Complete_Master_NT;

   Current_Master  : Get_Integer_Call :=  Current_Master_NT'Access;

   Enter_Master    : No_Param_Proc    :=  Enter_Master_NT'Access;

   Complete_Master : No_Param_Proc    :=  Complete_Master_NT'Access;

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

   -- Delay Soft-Links --

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

   --  Soft-Links are used for procedures that manipulate time to avoid

   --  dragging the tasking run time when using delay statements.

   Timed_Delay : Timed_Delay_Call;

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

   -- Task Name Soft-Links --

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

   function Task_Name_NT return String;

   Task_Name : Task_Name_Call := Task_Name_NT'Access;

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

   -- Exception Tracebacks Soft-Links --

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

   Library_Exception : EO;

   pragma Export (Ada, Library_Exception, "__gnat_library_exception");

   --  Library-level finalization routines use this common reference to store

   --  the first library-level exception which occurs during finalization.

   Library_Exception_Set : Boolean := False;

   pragma Export (Ada, Library_Exception_Set, "__gnat_library_exception_set");

   --  Used in conjunction with Library_Exception, set when an exception has

   --  been stored.

   Traceback_Decorator_Wrapper : Traceback_Decorator_Wrapper_Call;

   --  Wrapper to the possible user specified traceback decorator to be

   --  called during automatic output of exception data.

   --  The nullity of this wrapper shall correspond to the nullity of the

   --  current actual decorator. This is ensured first by the null initial

   --  value of the corresponding variables, and then by Set_Trace_Decorator

   --  in g-exctra.adb.

   pragma Atomic (Traceback_Decorator_Wrapper);

   --  Since concurrent read/write operations may occur on this variable.

   --  See the body of Tailored_Exception_Traceback in Ada.Exceptions for

   --  a more detailed description of the potential problems.

   procedure Save_Library_Occurrence (E : Ada.Exceptions.Exception_Occurrence);

   --  When invoked, this routine saves an exception occurrence into a hidden

   --  reference. Subsequent calls will have no effect.

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

   -- Task Specific Data --

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

   --  Here we define a single type that encapsulates the various task

   --  specific data. This type is used to store the necessary data into the

   --  Task_Control_Block or into a global variable in the non tasking case.

   type TSD is record

      Pri_Stack_Info : aliased Stack_Checking.Stack_Info;

      --  Information on stack (Base/Limit/Size) used by System.Stack_Checking.

      --  If this TSD does not belong to the environment task, the Size field

      --  must be initialized to the tasks requested stack size before the task

      --  can do its first stack check.

      pragma Warnings (Off);

      --  Needed because we are giving a non-static default to an object in

      --  a preelaborated unit, which is formally not permitted, but OK here.

      Jmpbuf_Address : System.Address := System.Null_Address;

      --  Address of jump buffer used to store the address of the current

      --  longjmp/setjmp buffer for exception management. These buffers are

      --  threaded into a stack, and the address here is the top of the stack.

      --  A null address means that no exception handler is currently active.

      Sec_Stack_Addr : System.Address := System.Null_Address;

      pragma Warnings (On);

      --  Address of currently allocated secondary stack

      Current_Excep : aliased EO;

      --  Exception occurrence that contains the information for the current

      --  exception. Note that any exception in the same task destroys this

      --  information, so the data in this variable must be copied out before

      --  another exception can occur.

      --

      --  Also act as a list of the active exceptions in the case of the GCC

      --  exception mechanism, organized as a stack with the most recent first.

   end record;

   procedure Create_TSD (New_TSD : in out TSD);

   pragma Inline (Create_TSD);

   --  Called from s-tassta when a new thread is created to perform

   --  any required initialization of the TSD.

   procedure Destroy_TSD (Old_TSD : in out TSD);

   pragma Inline (Destroy_TSD);

   --  Called from s-tassta just before a thread is destroyed to perform

   --  any required finalization.

   function Get_GNAT_Exception return Ada.Exceptions.Exception_Id;

   pragma Inline (Get_GNAT_Exception);

   --  This function obtains the Exception_Id from the Exception_Occurrence

   --  referenced by the Current_Excep field of the task specific data, i.e.

   --  the call is equivalent to

   --  Exception_Identity (Get_Current_Exception.all)

   --  Export the Get/Set routines for the various Task Specific Data (TSD)

   --  elements as callable subprograms instead of objects of access to

   --  subprogram types.

   function  Get_Jmpbuf_Address_Soft return  Address;

   procedure Set_Jmpbuf_Address_Soft (Addr : Address);

   pragma Inline (Get_Jmpbuf_Address_Soft);

   pragma Inline (Set_Jmpbuf_Address_Soft);

   function  Get_Sec_Stack_Addr_Soft return  Address;

   procedure Set_Sec_Stack_Addr_Soft (Addr : Address);

   pragma Inline (Get_Sec_Stack_Addr_Soft);

   pragma Inline (Set_Sec_Stack_Addr_Soft);

   --  The following is a dummy record designed to mimic Communication_Block as

   --  defined in s-tpobop.ads:

   --     type Communication_Block is record

   --        Self      : Task_Id;  --  An access type

   --        Enqueued  : Boolean := True;

   --        Cancelled : Boolean := False;

   --     end record;

   --  The record is used in the construction of the predefined dispatching

   --  primitive _disp_asynchronous_select in order to avoid the import of

   --  System.Tasking.Protected_Objects.Operations. Note that this package

   --  is always imported in the presence of interfaces since the dispatch

   --  table uses entities from here.

   type Dummy_Communication_Block is record

      Comp_1 : Address;  --  Address and access have the same size

      Comp_2 : Boolean;

      Comp_3 : Boolean;

   end record;

end System.Soft_Links;