1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT RUN-TIME COMPONENTS                         --
4--                                                                          --
5--                       A D A . E X C E P T I O N S                        --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--          Copyright (C) 1992-2015, Free Software Foundation, Inc.         --
10--                                                                          --
11-- This specification is derived from the Ada Reference Manual for use with --
12-- GNAT. The copyright notice above, and the license provisions that follow --
13-- apply solely to the  contents of the part following the private keyword. --
14--                                                                          --
15-- GNAT is free software;  you can  redistribute it  and/or modify it under --
16-- terms of the  GNU General Public License as published  by the Free Soft- --
17-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
18-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
19-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
20-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
21--                                                                          --
22-- As a special exception under Section 7 of GPL version 3, you are granted --
23-- additional permissions described in the GCC Runtime Library Exception,   --
24-- version 3.1, as published by the Free Software Foundation.               --
25--                                                                          --
26-- You should have received a copy of the GNU General Public License and    --
27-- a copy of the GCC Runtime Library Exception along with this program;     --
28-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
29-- <http://www.gnu.org/licenses/>.                                          --
30--                                                                          --
31-- GNAT was originally developed  by the GNAT team at  New York University. --
32-- Extensive contributions were provided by Ada Core Technologies Inc.      --
33--                                                                          --
34------------------------------------------------------------------------------
35
36--  This version of Ada.Exceptions fully supports Ada 95 and later language
37--  versions.  It is used in all situations except for the build of the
38--  compiler and other basic tools. For these latter builds, we use an
39--  Ada 95-only version.
40
41--  The reason for this splitting off of a separate version is to support
42--  older bootstrap compilers that do not support Ada 2005 features, and
43--  Ada.Exceptions is part of the compiler sources.
44
45pragma Polling (Off);
46--  We must turn polling off for this unit, because otherwise we get
47--  elaboration circularities with ourself.
48
49with System;
50with System.Parameters;
51with System.Standard_Library;
52with System.Traceback_Entries;
53
54package Ada.Exceptions is
55   pragma Preelaborate;
56   --  In accordance with Ada 2005 AI-362.
57
58   type Exception_Id is private;
59   pragma Preelaborable_Initialization (Exception_Id);
60
61   Null_Id : constant Exception_Id;
62
63   type Exception_Occurrence is limited private;
64   pragma Preelaborable_Initialization (Exception_Occurrence);
65
66   type Exception_Occurrence_Access is access all Exception_Occurrence;
67
68   Null_Occurrence : constant Exception_Occurrence;
69
70   function Exception_Name (Id : Exception_Id) return String;
71
72   function Exception_Name (X : Exception_Occurrence) return String;
73
74   function Wide_Exception_Name
75     (Id : Exception_Id) return Wide_String;
76   pragma Ada_05 (Wide_Exception_Name);
77
78   function Wide_Exception_Name
79     (X : Exception_Occurrence) return Wide_String;
80   pragma Ada_05 (Wide_Exception_Name);
81
82   function Wide_Wide_Exception_Name
83     (Id : Exception_Id) return Wide_Wide_String;
84   pragma Ada_05 (Wide_Wide_Exception_Name);
85
86   function Wide_Wide_Exception_Name
87     (X : Exception_Occurrence) return Wide_Wide_String;
88   pragma Ada_05 (Wide_Wide_Exception_Name);
89
90   procedure Raise_Exception (E : Exception_Id; Message : String := "");
91   pragma No_Return (Raise_Exception);
92   --  Note: In accordance with AI-466, CE is raised if E = Null_Id
93
94   function Exception_Message (X : Exception_Occurrence) return String;
95
96   procedure Reraise_Occurrence (X : Exception_Occurrence);
97   --  Note: it would be really nice to give a pragma No_Return for this
98   --  procedure, but it would be wrong, since Reraise_Occurrence does return
99   --  if the argument is the null exception occurrence. See also procedure
100   --  Reraise_Occurrence_Always in the private part of this package.
101
102   function Exception_Identity (X : Exception_Occurrence) return Exception_Id;
103
104   function Exception_Information (X : Exception_Occurrence) return String;
105   --  The format of the exception information is as follows:
106   --
107   --    exception name (as in Exception_Name)
108   --    message (or a null line if no message)
109   --    PID=nnnn
110   --    0xyyyyyyyy 0xyyyyyyyy ...
111   --
112   --  The lines are separated by a ASCII.LF character
113   --
114   --  The nnnn is the partition Id given as decimal digits
115   --
116   --  The 0x... line represents traceback program counter locations,
117   --  in order with the first one being the exception location.
118
119   --  Note on ordering: the compiler uses the Save_Occurrence procedure, but
120   --  not the function from Rtsfind, so it is important that the procedure
121   --  come first, since Rtsfind finds the first matching entity.
122
123   procedure Save_Occurrence
124     (Target : out Exception_Occurrence;
125      Source : Exception_Occurrence);
126
127   function Save_Occurrence
128     (Source : Exception_Occurrence)
129      return   Exception_Occurrence_Access;
130
131   --  Ada 2005 (AI-438): The language revision introduces the following
132   --  subprograms and attribute definitions. We do not provide them
133   --  explicitly. instead, the corresponding stream attributes are made
134   --  available through a pragma Stream_Convert in the private part.
135
136   --  procedure Read_Exception_Occurrence
137   --    (Stream : not null access Ada.Streams.Root_Stream_Type'Class;
138   --     Item   : out Exception_Occurrence);
139
140   --  procedure Write_Exception_Occurrence
141   --    (Stream : not null access Ada.Streams.Root_Stream_Type'Class;
142   --     Item   : Exception_Occurrence);
143
144   --  for Exception_Occurrence'Read use Read_Exception_Occurrence;
145   --  for Exception_Occurrence'Write use Write_Exception_Occurrence;
146
147private
148   package SSL renames System.Standard_Library;
149   package SP renames System.Parameters;
150
151   subtype EOA is Exception_Occurrence_Access;
152
153   Exception_Msg_Max_Length : constant := SP.Default_Exception_Msg_Max_Length;
154
155   ------------------
156   -- Exception_Id --
157   ------------------
158
159   subtype Code_Loc is System.Address;
160   --  Code location used in building exception tables and for call addresses
161   --  when propagating an exception. Values of this type are created by using
162   --  Label'Address or extracted from machine states using Get_Code_Loc.
163
164   Null_Loc : constant Code_Loc := System.Null_Address;
165   --  Null code location, used to flag outer level frame
166
167   type Exception_Id is new SSL.Exception_Data_Ptr;
168
169   function EId_To_String (X : Exception_Id) return String;
170   function String_To_EId (S : String) return Exception_Id;
171   pragma Stream_Convert (Exception_Id, String_To_EId, EId_To_String);
172   --  Functions for implementing Exception_Id stream attributes
173
174   Null_Id : constant Exception_Id := null;
175
176   -------------------------
177   -- Private Subprograms --
178   -------------------------
179
180   function Exception_Name_Simple (X : Exception_Occurrence) return String;
181   --  Like Exception_Name, but returns the simple non-qualified name of the
182   --  exception. This is used to implement the Exception_Name function in
183   --  Current_Exceptions (the DEC compatible unit). It is called from the
184   --  compiler generated code (using Rtsfind, which does not respect the
185   --  private barrier, so we can place this function in the private part
186   --  where the compiler can find it, but the spec is unchanged.)
187
188   procedure Raise_Exception_Always (E : Exception_Id; Message : String := "");
189   pragma No_Return (Raise_Exception_Always);
190   pragma Export (Ada, Raise_Exception_Always, "__gnat_raise_exception");
191   --  This differs from Raise_Exception only in that the caller has determined
192   --  that for sure the parameter E is not null, and that therefore no check
193   --  for Null_Id is required. The expander converts Raise_Exception calls to
194   --  Raise_Exception_Always if it can determine this is the case. The Export
195   --  allows this routine to be accessed from Pure units.
196
197   procedure Raise_From_Signal_Handler
198     (E : Exception_Id;
199      M : System.Address);
200   pragma Export
201     (Ada, Raise_From_Signal_Handler,
202           "ada__exceptions__raise_from_signal_handler");
203   pragma No_Return (Raise_From_Signal_Handler);
204   --  This routine is used to raise an exception from a signal handler. The
205   --  signal handler has already stored the machine state (i.e. the state that
206   --  corresponds to the location at which the signal was raised). E is the
207   --  Exception_Id specifying what exception is being raised, and M is a
208   --  pointer to a null-terminated string which is the message to be raised.
209   --  Note that this routine never returns, so it is permissible to simply
210   --  jump to this routine, rather than call it. This may be appropriate for
211   --  systems where the right way to get out of signal handler is to alter the
212   --  PC value in the machine state or in some other way ask the operating
213   --  system to return here rather than to the original location.
214
215   procedure Raise_From_Controlled_Operation
216     (X : Ada.Exceptions.Exception_Occurrence);
217   pragma No_Return (Raise_From_Controlled_Operation);
218   pragma Export
219     (Ada, Raise_From_Controlled_Operation,
220           "__gnat_raise_from_controlled_operation");
221   --  Raise Program_Error, providing information about X (an exception raised
222   --  during a controlled operation) in the exception message.
223
224   procedure Reraise_Library_Exception_If_Any;
225   pragma Export
226     (Ada, Reraise_Library_Exception_If_Any,
227           "__gnat_reraise_library_exception_if_any");
228   --  If there was an exception raised during library-level finalization,
229   --  reraise the exception.
230
231   procedure Reraise_Occurrence_Always (X : Exception_Occurrence);
232   pragma No_Return (Reraise_Occurrence_Always);
233   --  This differs from Raise_Occurrence only in that the caller guarantees
234   --  that for sure the parameter X is not the null occurrence, and that
235   --  therefore this procedure cannot return. The expander uses this routine
236   --  in the translation of a raise statement with no parameter (reraise).
237
238   procedure Reraise_Occurrence_No_Defer (X : Exception_Occurrence);
239   pragma No_Return (Reraise_Occurrence_No_Defer);
240   --  Exactly like Reraise_Occurrence, except that abort is not deferred
241   --  before the call and the parameter X is known not to be the null
242   --  occurrence. This is used in generated code when it is known that abort
243   --  is already deferred.
244
245   function Triggered_By_Abort return Boolean;
246   --  Determine whether the current exception (if it exists) is an instance of
247   --  Standard'Abort_Signal.
248
249   -----------------------
250   -- Polling Interface --
251   -----------------------
252
253   --  The GNAT compiler has an option to generate polling calls to the Poll
254   --  routine in this package. Specifying the -gnatP option for a compilation
255   --  causes a call to Ada.Exceptions.Poll to be generated on every subprogram
256   --  entry and on every iteration of a loop, thus avoiding the possibility of
257   --  a case of unbounded time between calls.
258
259   --  This polling interface may be used for instrumentation or debugging
260   --  purposes (e.g. implementing watchpoints in software or in the debugger).
261
262   --  In the GNAT technology itself, this interface is used to implement
263   --  immediate asynchronous transfer of control and immediate abort on
264   --  targets which do not provide for one thread interrupting another.
265
266   --  Note: this used to be in a separate unit called System.Poll, but that
267   --  caused horrible circular elaboration problems between System.Poll and
268   --  Ada.Exceptions.
269
270   procedure Poll;
271   --  Check for asynchronous abort. Note that we do not inline the body.
272   --  This makes the interface more useful for debugging purposes.
273
274   --------------------------
275   -- Exception_Occurrence --
276   --------------------------
277
278   package TBE renames System.Traceback_Entries;
279
280   Max_Tracebacks : constant := 50;
281   --  Maximum number of trace backs stored in exception occurrence
282
283   subtype Tracebacks_Array is TBE.Tracebacks_Array (1 .. Max_Tracebacks);
284   --  Traceback array stored in exception occurrence
285
286   type Exception_Occurrence is record
287      Id : Exception_Id;
288      --  Exception_Identity for this exception occurrence
289
290      Machine_Occurrence : System.Address;
291      --  The underlying machine occurrence. For GCC, this corresponds to the
292      --  _Unwind_Exception structure address.
293
294      Msg_Length : Natural := 0;
295      --  Length of message (zero = no message)
296
297      Msg : String (1 .. Exception_Msg_Max_Length);
298      --  Characters of message
299
300      Exception_Raised : Boolean := False;
301      --  Set to true to indicate that this exception occurrence has actually
302      --  been raised. When an exception occurrence is first created, this is
303      --  set to False, then when it is processed by Raise_Current_Exception,
304      --  it is set to True. If Raise_Current_Exception is used to raise an
305      --  exception for which this flag is already True, then it knows that
306      --  it is dealing with the reraise case (which is useful to distinguish
307      --  for exception tracing purposes).
308
309      Pid : Natural := 0;
310      --  Partition_Id for partition raising exception
311
312      Num_Tracebacks : Natural range 0 .. Max_Tracebacks := 0;
313      --  Number of traceback entries stored
314
315      Tracebacks : Tracebacks_Array;
316      --  Stored tracebacks (in Tracebacks (1 .. Num_Tracebacks))
317   end record;
318
319   function "=" (Left, Right : Exception_Occurrence) return Boolean
320     is abstract;
321   --  Don't allow comparison on exception occurrences, we should not need
322   --  this, and it would not work right, because of the Msg and Tracebacks
323   --  fields which have unused entries not copied by Save_Occurrence.
324
325   function Get_Exception_Machine_Occurrence
326     (X : Exception_Occurrence) return System.Address;
327   pragma Export (Ada, Get_Exception_Machine_Occurrence,
328                  "__gnat_get_exception_machine_occurrence");
329   --  Get the machine occurrence corresponding to an exception occurrence.
330   --  It is Null_Address if there is no machine occurrence (in runtimes that
331   --  doesn't use GCC mechanism) or if it has been lost (Save_Occurrence
332   --  doesn't save the machine occurrence).
333
334   function EO_To_String (X : Exception_Occurrence) return String;
335   function String_To_EO (S : String) return Exception_Occurrence;
336   pragma Stream_Convert (Exception_Occurrence, String_To_EO, EO_To_String);
337   --  Functions for implementing Exception_Occurrence stream attributes
338
339   Null_Occurrence : constant Exception_Occurrence := (
340     Id                 => null,
341     Machine_Occurrence => System.Null_Address,
342     Msg_Length         => 0,
343     Msg                => (others => ' '),
344     Exception_Raised   => False,
345     Pid                => 0,
346     Num_Tracebacks     => 0,
347     Tracebacks         => (others => TBE.Null_TB_Entry));
348
349end Ada.Exceptions;
350