File : a-except-2005.ads
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 -- --
23 -- --
24 -- --
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
45 pragma Polling (Off);
46 -- We must turn polling off for this unit, because otherwise we get
47 -- elaboration circularities with ourself.
48
49 with System;
50 with System.Parameters;
51 with System.Standard_Library;
52 with System.Traceback_Entries;
53
54 package 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
147 private
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
349 end Ada.Exceptions;