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

--                                                                          --

--                         GNAT RUN-TIME COMPONENTS                         --

--                                                                          --

--                       A D A . E X C E P T I O N S                        --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 1992-2009, Free Software Foundation, Inc.         --

--                                                                          --

-- This specification is derived from the Ada Reference Manual for use with --

-- GNAT. The copyright notice above, and the license provisions that follow --

-- apply solely to the  contents of the part following the private keyword. --

--                                                                          --

-- 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 version of Ada.Exceptions is a full Ada 95 version. It omits Ada 2005

--  features such as the additional definitions of Exception_Name returning

--  Wide_[Wide_]String.

--  It is used for building the compiler and the basic tools, since these

--  builds may be done with bootstrap compilers that cannot handle these

--  additions. The full version of Ada.Exceptions can be found in the files

--  a-except-2005.ads/adb, and is used for all other builds where full Ada

--  2005 functionality is required. In particular, it is used for building

--  run times on all targets.

pragma Compiler_Unit;

pragma Polling (Off);

--  We must turn polling off for this unit, because otherwise we get

--  elaboration circularities with ourself.

with System;

with System.Parameters;

with System.Standard_Library;

with System.Traceback_Entries;

package Ada.Exceptions is

   pragma Warnings (Off);

   pragma Preelaborate_05;

   pragma Warnings (On);

   --  We make this preelaborable in Ada 2005 mode. If we did not do this, then

   --  run time units used by the compiler (e.g. s-soflin.ads) would run

   --  into trouble. Conformance is not an issue, since this version is used

   --  only by the compiler.

   type Exception_Id is private;

   Null_Id : constant Exception_Id;

   type Exception_Occurrence is limited private;

   type Exception_Occurrence_Access is access all Exception_Occurrence;

   Null_Occurrence : constant Exception_Occurrence;

   function Exception_Name (X : Exception_Occurrence) return String;

   --  Same as Exception_Name (Exception_Identity (X))

   function Exception_Name (Id : Exception_Id) return String;

   procedure Raise_Exception (E : Exception_Id; Message : String := "");

   pragma No_Return (Raise_Exception);

   --  Note: In accordance with AI-466, CE is raised if E = Null_Id

   function Exception_Message (X : Exception_Occurrence) return String;

   procedure Reraise_Occurrence (X : Exception_Occurrence);

   --  Note: it would be really nice to give a pragma No_Return for this

   --  procedure, but it would be wrong, since Reraise_Occurrence does return

   --  if the argument is the null exception occurrence. See also procedure

   --  Reraise_Occurrence_Always in the private part of this package.

   function Exception_Identity (X : Exception_Occurrence) return Exception_Id;

   function Exception_Information (X : Exception_Occurrence) return String;

   --  The format of the exception information is as follows:

   --

   --    exception name (as in Exception_Name)

   --    message (or a null line if no message)

   --    PID=nnnn

   --    0xyyyyyyyy 0xyyyyyyyy ...

   --

   --  The lines are separated by a ASCII.LF character

   --  The nnnn is the partition Id given as decimal digits.

   --  The 0x... line represents traceback program counter locations,

   --  in order with the first one being the exception location.

   --  Note on ordering: the compiler uses the Save_Occurrence procedure, but

   --  not the function from Rtsfind, so it is important that the procedure

   --  come first, since Rtsfind finds the first matching entity.

   procedure Save_Occurrence

     (Target : out Exception_Occurrence;

      Source : Exception_Occurrence);

   function Save_Occurrence

     (Source : Exception_Occurrence)

      return   Exception_Occurrence_Access;

private

   package SSL renames System.Standard_Library;

   package SP renames System.Parameters;

   subtype EOA is Exception_Occurrence_Access;

   Exception_Msg_Max_Length : constant := SP.Default_Exception_Msg_Max_Length;

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

   -- Exception_Id --

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

   subtype Code_Loc is System.Address;

   --  Code location used in building exception tables and for call addresses

   --  when propagating an exception. Values of this type are created by using

   --  Label'Address or extracted from machine states using Get_Code_Loc.

   Null_Loc : constant Code_Loc := System.Null_Address;

   --  Null code location, used to flag outer level frame

   type Exception_Id is new SSL.Exception_Data_Ptr;

   function EId_To_String (X : Exception_Id) return String;

   function String_To_EId (S : String) return Exception_Id;

   pragma Stream_Convert (Exception_Id, String_To_EId, EId_To_String);

   --  Functions for implementing Exception_Id stream attributes

   Null_Id : constant Exception_Id := null;

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

   -- Private Subprograms --

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

   function Current_Target_Exception return Exception_Occurrence;

   pragma Export

     (Ada, Current_Target_Exception,

      "__gnat_current_target_exception");

   --  This routine should return the current raised exception on targets

   --  which have built-in exception handling such as the Java Virtual

   --  Machine. For other targets this routine is simply ignored. Currently,

   --  only JGNAT uses this. See 4jexcept.ads for details. The pragma Export

   --  allows this routine to be accessed elsewhere in the run-time, even

   --  though it is in the private part of this package (it is not allowed

   --  to be in the visible part, since this is set by the reference manual).

   function Exception_Name_Simple (X : Exception_Occurrence) return String;

   --  Like Exception_Name, but returns the simple non-qualified name of the

   --  exception. This is used to implement the Exception_Name function in

   --  Current_Exceptions (the DEC compatible unit). It is called from the

   --  compiler generated code (using Rtsfind, which does not respect the

   --  private barrier, so we can place this function in the private part

   --  where the compiler can find it, but the spec is unchanged.)

   procedure Raise_Exception_Always (E : Exception_Id; Message : String := "");

   pragma No_Return (Raise_Exception_Always);

   pragma Export (Ada, Raise_Exception_Always, "__gnat_raise_exception");

   --  This differs from Raise_Exception only in that the caller has determined

   --  that for sure the parameter E is not null, and that therefore no check

   --  for Null_Id is required. The expander converts Raise_Exception calls to

   --  Raise_Exception_Always if it can determine this is the case. The Export

   --  allows this routine to be accessed from Pure units.

   procedure Raise_From_Signal_Handler

     (E : Exception_Id;

      M : System.Address);

   pragma Export

     (Ada, Raise_From_Signal_Handler,

           "ada__exceptions__raise_from_signal_handler");

   pragma No_Return (Raise_From_Signal_Handler);

   --  This routine is used to raise an exception from a signal handler. The

   --  signal handler has already stored the machine state (i.e. the state that

   --  corresponds to the location at which the signal was raised). E is the

   --  Exception_Id specifying what exception is being raised, and M is a

   --  pointer to a null-terminated string which is the message to be raised.

   --  Note that this routine never returns, so it is permissible to simply

   --  jump to this routine, rather than call it. This may be appropriate for

   --  systems where the right way to get out of signal handler is to alter the

   --  PC value in the machine state or in some other way ask the operating

   --  system to return here rather than to the original location.

   procedure Raise_From_Controlled_Operation

     (X : Ada.Exceptions.Exception_Occurrence);

   pragma No_Return (Raise_From_Controlled_Operation);

   --  Raise Program_Error, providing information about X (an exception

   --  raised during a controlled operation) in the exception message.

   procedure Reraise_Occurrence_Always (X : Exception_Occurrence);

   pragma No_Return (Reraise_Occurrence_Always);

   --  This differs from Raise_Occurrence only in that the caller guarantees

   --  that for sure the parameter X is not the null occurrence, and that

   --  therefore this procedure cannot return. The expander uses this routine

   --  in the translation of a raise statement with no parameter (reraise).

   procedure Reraise_Occurrence_No_Defer (X : Exception_Occurrence);

   pragma No_Return (Reraise_Occurrence_No_Defer);

   --  Exactly like Reraise_Occurrence, except that abort is not deferred

   --  before the call and the parameter X is known not to be the null

   --  occurrence. This is used in generated code when it is known that

   --  abort is already deferred.

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

   -- Polling Interface --

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

   --  The GNAT compiler has an option to generate polling calls to the Poll

   --  routine in this package. Specifying the -gnatP option for a compilation

   --  causes a call to Ada.Exceptions.Poll to be generated on every subprogram

   --  entry and on every iteration of a loop, thus avoiding the possibility of

   --  a case of unbounded time between calls.

   --  This polling interface may be used for instrumentation or debugging

   --  purposes (e.g. implementing watchpoints in software or in the debugger).

   --  In the GNAT technology itself, this interface is used to implement

   --  immediate asynchronous transfer of control and immediate abort on

   --  targets which do not provide for one thread interrupting another.

   --  Note: this used to be in a separate unit called System.Poll, but that

   --  caused horrible circular elaboration problems between System.Poll and

   --  Ada.Exceptions. One way of solving such circularities is unification!

   procedure Poll;

   --  Check for asynchronous abort. Note that we do not inline the body.

   --  This makes the interface more useful for debugging purposes.

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

   -- Exception_Occurrence --

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

   package TBE renames System.Traceback_Entries;

   Max_Tracebacks : constant := 50;

   --  Maximum number of trace backs stored in exception occurrence

   type Tracebacks_Array is array (1 .. Max_Tracebacks) of TBE.Traceback_Entry;

   --  Traceback array stored in exception occurrence

   type Exception_Occurrence is record

      Id : Exception_Id;

      --  Exception_Identity for this exception occurrence

      --  WARNING System.System.Finalization_Implementation.Finalize_List

      --  relies on the fact that this field is always first in the exception

      --  occurrence

      Msg_Length : Natural := 0;

      --  Length of message (zero = no message)

      Msg : String (1 .. Exception_Msg_Max_Length);

      --  Characters of message

      Cleanup_Flag : Boolean := False;

      --  The cleanup flag is normally False, it is set True for an exception

      --  occurrence passed to a cleanup routine, and will still be set True

      --  when the cleanup routine does a Reraise_Occurrence call using this

      --  exception occurrence. This is used to avoid recording a bogus trace

      --  back entry from this reraise call.

      Exception_Raised : Boolean := False;

      --  Set to true to indicate that this exception occurrence has actually

      --  been raised. When an exception occurrence is first created, this is

      --  set to False, then when it is processed by Raise_Current_Exception,

      --  it is set to True. If Raise_Current_Exception is used to raise an

      --  exception for which this flag is already True, then it knows that

      --  it is dealing with the reraise case (which is useful to distinguish

      --  for exception tracing purposes).

      Pid : Natural := 0;

      --  Partition_Id for partition raising exception

      Num_Tracebacks : Natural range 0 .. Max_Tracebacks := 0;

      --  Number of traceback entries stored

      Tracebacks : Tracebacks_Array;

      --  Stored tracebacks (in Tracebacks (1 .. Num_Tracebacks))

      Private_Data : System.Address := System.Null_Address;

      --  Field used by low level exception mechanism to store specific data.

      --  Currently used by the GCC exception mechanism to store a pointer to

      --  a GNAT_GCC_Exception.

   end record;

   function "=" (Left, Right : Exception_Occurrence) return Boolean

     is abstract;

   --  Don't allow comparison on exception occurrences, we should not need

   --  this, and it would not work right, because of the Msg and Tracebacks

   --  fields which have unused entries not copied by Save_Occurrence.

   function EO_To_String (X : Exception_Occurrence) return String;

   function String_To_EO (S : String) return Exception_Occurrence;

   pragma Stream_Convert (Exception_Occurrence, String_To_EO, EO_To_String);

   --  Functions for implementing Exception_Occurrence stream attributes

   Null_Occurrence : constant Exception_Occurrence := (

     Id               => null,

     Msg_Length       => 0,

     Msg              => (others => ' '),

     Cleanup_Flag     => False,

     Exception_Raised => False,

     Pid              => 0,

     Num_Tracebacks   => 0,

     Tracebacks       => (others => TBE.Null_TB_Entry),

     Private_Data     => System.Null_Address);

end Ada.Exceptions;