347 lines
17 KiB
Ada
347 lines
17 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME COMPONENTS --
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-- --
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-- A D A . E X C E P T I O N S --
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-- --
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-- S p e c --
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-- --
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-- $Revision: 1.50 $
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-- --
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-- Copyright (C) 1992-2001 Free Software Foundation, Inc. --
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-- --
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-- This specification is derived from the Ada Reference Manual for use with --
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-- GNAT. The copyright notice above, and the license provisions that follow --
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-- apply solely to the contents of the part following the private keyword. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 2, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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-- for more details. You should have received a copy of the GNU General --
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-- Public License distributed with GNAT; see file COPYING. If not, write --
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-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
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-- MA 02111-1307, USA. --
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-- --
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-- As a special exception, if other files instantiate generics from this --
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-- unit, or you link this unit with other files to produce an executable, --
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-- this unit does not by itself cause the resulting executable to be --
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-- covered by the GNU General Public License. This exception does not --
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-- however invalidate any other reasons why the executable file might be --
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-- covered by the GNU Public License. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
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-- --
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------------------------------------------------------------------------------
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pragma Polling (Off);
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-- We must turn polling off for this unit, because otherwise we get
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-- elaboration circularities with ourself.
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with System;
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with System.Standard_Library;
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package Ada.Exceptions is
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type Exception_Id is private;
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Null_Id : constant Exception_Id;
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type Exception_Occurrence is limited private;
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type Exception_Occurrence_Access is access all Exception_Occurrence;
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Null_Occurrence : constant Exception_Occurrence;
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function Exception_Name (X : Exception_Occurrence) return String;
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-- Same as Exception_Name (Exception_Identity (X))
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function Exception_Name (Id : Exception_Id) return String;
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procedure Raise_Exception (E : Exception_Id; Message : String := "");
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-- Note: it would be really nice to give a pragma No_Return for this
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-- procedure, but it would be wrong, since Raise_Exception does return
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-- if given the null exception. However we do special case the name in
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-- the test in the compiler for issuing a warning for a missing return
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-- after this call. Program_Error seems reasonable enough in such a case.
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-- See also the routine Raise_Exception_Always in the private part.
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function Exception_Message (X : Exception_Occurrence) return String;
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procedure Reraise_Occurrence (X : Exception_Occurrence);
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-- Note: it would be really nice to give a pragma No_Return for this
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-- procedure, but it would be wrong, since Reraise_Occurrence does return
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-- if the argument is the null exception occurrence. See also procedure
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-- Reraise_Occurrence_Always in the private part of this package.
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function Exception_Identity (X : Exception_Occurrence) return Exception_Id;
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function Exception_Information (X : Exception_Occurrence) return String;
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-- The format of the exception information is as follows:
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--
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-- exception name (as in Exception_Name)
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-- message (or a null line if no message)
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-- PID=nnnn
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-- 0xyyyyyyyy 0xyyyyyyyy ...
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--
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-- The lines are separated by an ASCII.CR/ASCII.LF sequence.
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-- The nnnn is the partition Id given as decimal digits.
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-- The 0x... line represents traceback program counter locations,
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-- in order with the first one being the exception location.
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-- Note on ordering: the compiler uses the Save_Occurrence procedure, but
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-- not the function from Rtsfind, so it is important that the procedure
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-- come first, since Rtsfind finds the first matching entity.
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procedure Save_Occurrence
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(Target : out Exception_Occurrence;
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Source : Exception_Occurrence);
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function Save_Occurrence
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(Source : Exception_Occurrence)
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return Exception_Occurrence_Access;
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private
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package SSL renames System.Standard_Library;
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subtype EOA is Exception_Occurrence_Access;
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Exception_Msg_Max_Length : constant := 200;
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------------------
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-- Exception_Id --
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------------------
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subtype Code_Loc is System.Address;
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-- Code location used in building exception tables and for call
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-- addresses when propagating an exception (also traceback table)
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-- Values of this type are created by using Label'Address or
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-- extracted from machine states using Get_Code_Loc.
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Null_Loc : constant Code_Loc := System.Null_Address;
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-- Null code location, used to flag outer level frame
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type Exception_Id is new SSL.Exception_Data_Ptr;
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function EId_To_String (X : Exception_Id) return String;
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function String_To_EId (S : String) return Exception_Id;
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pragma Stream_Convert (Exception_Id, String_To_EId, EId_To_String);
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-- Functions for implementing Exception_Id stream attributes
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Null_Id : constant Exception_Id := null;
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-------------------------
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-- Private Subprograms --
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-------------------------
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function Current_Target_Exception return Exception_Occurrence;
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pragma Export
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(Ada, Current_Target_Exception,
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"__gnat_current_target_exception");
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-- This routine should return the current raised exception on targets
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-- which have built-in exception handling such as the Java Virtual
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-- Machine. For other targets this routine is simply ignored. Currently,
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-- only JGNAT uses this. See 4jexcept.ads for details. The pragma Export
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-- allows this routine to be accessed elsewhere in the run-time, even
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-- though it is in the private part of this package (it is not allowed
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-- to be in the visible part, since this is set by the reference manual).
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function Exception_Name_Simple (X : Exception_Occurrence) return String;
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-- Like Exception_Name, but returns the simple non-qualified name of
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-- the exception. This is used to implement the Exception_Name function
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-- in Current_Exceptions (the DEC compatible unit). It is called from
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-- the compiler generated code (using Rtsfind, which does not respect
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-- the private barrier, so we can place this function in the private
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-- part where the compiler can find it, but the spec is unchanged.)
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procedure Raise_Exception_Always (E : Exception_Id; Message : String := "");
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pragma No_Return (Raise_Exception_Always);
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pragma Export (Ada, Raise_Exception_Always, "__gnat_raise_exception");
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-- This differs from Raise_Exception only in that the caller has determined
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-- that for sure the parameter E is not null, and that therefore the call
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-- to this procedure cannot return. The expander converts Raise_Exception
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-- calls to Raise_Exception_Always if it can determine this is the case.
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-- The Export allows this routine to be accessed from Pure units.
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procedure Raise_No_Msg (E : Exception_Id);
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pragma No_Return (Raise_No_Msg);
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-- Raises an exception with no message with given exception id value.
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-- Abort is deferred before the raise call.
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procedure Raise_From_Signal_Handler
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(E : Exception_Id;
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M : SSL.Big_String_Ptr);
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pragma Export
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(Ada, Raise_From_Signal_Handler,
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"ada__exceptions__raise_from_signal_handler");
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pragma No_Return (Raise_From_Signal_Handler);
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-- This routine is used to raise an exception from a signal handler.
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-- The signal handler has already stored the machine state (i.e. the
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-- state that corresponds to the location at which the signal was
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-- raised). E is the Exception_Id specifying what exception is being
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-- raised, and M is a pointer to a null-terminated string which is the
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-- message to be raised. Note that this routine never returns, so it is
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-- permissible to simply jump to this routine, rather than call it. This
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-- may be appropriate for systems where the right way to get out of a
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-- signal handler is to alter the PC value in the machine state or in
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-- some other way ask the operating system to return here rather than
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-- to the original location.
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procedure Raise_With_C_Msg
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(E : Exception_Id;
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M : SSL.Big_String_Ptr);
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pragma Export (Ada, Raise_With_C_Msg, "ada__exceptions__raise_with_c_msg");
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pragma No_Return (Raise_With_C_Msg);
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-- Raises an exception with with given exception id value and message.
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-- M is a null terminated string with the message to be raised. Abort
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-- is deferred before the raise call.
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procedure Reraise_Occurrence_Always (X : Exception_Occurrence);
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pragma No_Return (Reraise_Occurrence_Always);
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-- This differs from Raise_Occurrence only in that the caller guarantees
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-- that for sure the parameter X is not the null occurrence, and that
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-- therefore this procedure cannot return. The expander uses this routine
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-- in the translation of a raise statement with no parameter (reraise).
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procedure Reraise_Occurrence_No_Defer (X : Exception_Occurrence);
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pragma No_Return (Reraise_Occurrence_No_Defer);
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-- Exactly like Reraise_Occurrence, except that abort is not deferred
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-- before the call and the parameter X is known not to be the null
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-- occurrence. This is used in generated code when it is known
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-- that abort is already deferred.
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procedure SDP_Table_Build
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(SDP_Addresses : System.Address;
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SDP_Count : Natural;
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Elab_Addresses : System.Address;
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Elab_Addr_Count : Natural);
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pragma Export (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
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-- This is the routine that is called to build and sort the list of
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-- subprogram descriptor pointers. In the normal case it is called
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-- once at the start of execution, but it can also be called as part
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-- of the explicit initialization routine (adainit) when there is no
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-- Ada main program. In particular, in the case where multiple Ada
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-- libraries are present, this routine can be called more than once
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-- for each library, in which case it augments the previously set
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-- table with the new entries specified by the parameters.
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--
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-- SDP_Addresses Address of the start of the list of addresses of
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-- __gnat_unit_name__SDP values constructed for each
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-- unit, (see System.Exceptions).
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--
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-- SDP_Count Number of entries in SDP_Addresses
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--
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-- Elab_Addresses Address of the start of a list of addresses of
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-- generated Ada elaboration routines, as well as
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-- one extra entry for the generated main program.
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-- These are used to generate the dummy SDP's that
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-- mark the outer scope.
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--
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-- Elab_Addr_Count Number of entries in Elab_Addresses
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procedure Break_Start;
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pragma Export (C, Break_Start, "__gnat_break_start");
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-- This is a dummy procedure that is called at the start of execution.
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-- Its sole purpose is to provide a well defined point for the placement
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-- of a main program breakpoint. We put the routine in Ada.Exceptions so
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-- that the standard mechanism of always stepping up from breakpoints
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-- within Ada.Exceptions leaves us sitting in the main program.
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-----------------------
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-- Polling Interface --
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-----------------------
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-- The GNAT compiler has an option to generate polling calls to the Poll
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-- routine in this package. Specifying the -gnatP option for a compilation
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-- causes a call to Ada.Exceptions.Poll to be generated on every subprogram
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-- entry and on every iteration of a loop, thus avoiding the possibility of
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-- a case of unbounded time between calls.
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-- This polling interface may be used for instrumentation or debugging
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-- purposes (e.g. implementing watchpoints in software or in the debugger).
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-- In the GNAT technology itself, this interface is used to implement
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-- immediate aynschronous transfer of control and immediate abort on
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-- targets which do not provide for one thread interrupting another.
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-- Note: this used to be in a separate unit called System.Poll, but that
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-- caused horrible circular elaboration problems between System.Poll and
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-- Ada.Exceptions. One way of solving such circularities is unification!
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procedure Poll;
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-- Check for asynchronous abort. Note that we do not inline the body.
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-- This makes the interface more useful for debugging purposes.
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--------------------------
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-- Exception_Occurrence --
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--------------------------
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Max_Tracebacks : constant := 50;
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-- Maximum number of trace backs stored in exception occurrence
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type Tracebacks_Array is array (1 .. Max_Tracebacks) of Code_Loc;
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-- Traceback array stored in exception occurrence
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type Exception_Occurrence is record
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Id : Exception_Id;
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-- Exception_Identity for this exception occurrence
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-- WARNING System.System.Finalization_Implementation.Finalize_List
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-- relies on the fact that this field is always first in the exception
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-- occurrence
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Msg_Length : Natural := 0;
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-- Length of message (zero = no message)
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Msg : String (1 .. Exception_Msg_Max_Length);
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-- Characters of message
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Cleanup_Flag : Boolean;
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-- The cleanup flag is normally False, it is set True for an exception
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-- occurrence passed to a cleanup routine, and will still be set True
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-- when the cleanup routine does a Reraise_Occurrence call using this
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-- exception occurrence. This is used to avoid recording a bogus trace
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-- back entry from this reraise call.
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Exception_Raised : Boolean := False;
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-- Set to true to indicate that this exception occurrence has actually
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-- been raised. When an exception occurrence is first created, this is
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-- set to False, then when it is processed by Raise_Current_Exception,
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-- it is set to True. If Raise_Current_Exception is used to raise an
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-- exception for which this flag is already True, then it knows that
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-- it is dealing with the reraise case (which is useful to distinguish
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-- for exception tracing purposes).
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Pid : Natural;
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-- Partition_Id for partition raising exception
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Num_Tracebacks : Natural range 0 .. Max_Tracebacks := 0;
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-- Number of traceback entries stored
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Tracebacks : Tracebacks_Array;
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-- Stored tracebacks (in Tracebacks (1 .. Num_Tracebacks))
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end record;
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function "=" (Left, Right : Exception_Occurrence) return Boolean
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is abstract;
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-- Don't allow comparison on exception occurrences, we should not need
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-- this, and it would not work right, because of the Msg and Tracebacks
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-- fields which have unused entries not copied by Save_Occurrence.
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function EO_To_String (X : Exception_Occurrence) return String;
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function String_To_EO (S : String) return Exception_Occurrence;
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pragma Stream_Convert (Exception_Occurrence, String_To_EO, EO_To_String);
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-- Functions for implementing Exception_Occurrence stream attributes
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Null_Occurrence : constant Exception_Occurrence := (
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Id => Null_Id,
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Msg_Length => 0,
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Msg => (others => ' '),
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Cleanup_Flag => False,
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Exception_Raised => False,
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Pid => 0,
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Num_Tracebacks => 0,
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Tracebacks => (others => Null_Loc));
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end Ada.Exceptions;
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