1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- A D A . E X C E P T I O N S --
9 -- Copyright (C) 1992-2008, Free Software Foundation, Inc. --
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. --
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 2, 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. See the GNU General Public License --
21 -- for more details. You should have received a copy of the GNU General --
22 -- Public License distributed with GNAT; see file COPYING. If not, write --
23 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
24 -- Boston, MA 02110-1301, USA. --
26 -- As a special exception, if other files instantiate generics from this --
27 -- unit, or you link this unit with other files to produce an executable, --
28 -- this unit does not by itself cause the resulting executable to be --
29 -- covered by the GNU General Public License. This exception does not --
30 -- however invalidate any other reasons why the executable file might be --
31 -- covered by the GNU Public License. --
33 -- GNAT was originally developed by the GNAT team at New York University. --
34 -- Extensive contributions were provided by Ada Core Technologies Inc. --
36 ------------------------------------------------------------------------------
38 -- This version of Ada.Exceptions fully supports both Ada 95 and Ada 2005.
39 -- It is used in all situations except for the build of the compiler and
40 -- other basic tools. For these latter builds, we use an Ada 95-only version.
42 -- The reason for this splitting off of a separate version is that bootstrap
43 -- compilers often will be used that do not support Ada 2005 features, and
44 -- Ada.Exceptions is part of the compiler sources.
47 -- We must turn polling off for this unit, because otherwise we get
48 -- elaboration circularities with ourself.
51 with System.Parameters;
52 with System.Standard_Library;
53 with System.Traceback_Entries;
55 package Ada.Exceptions is
56 pragma Warnings (Off);
57 pragma Preelaborate_05;
59 -- In accordance with Ada 2005 AI-362. The warnings pragmas are so that we
60 -- can compile this using older compiler versions, which will ignore the
61 -- pragma, which is fine for the bootstrap.
63 type Exception_Id is private;
64 pragma Preelaborable_Initialization (Exception_Id);
66 Null_Id : constant Exception_Id;
68 type Exception_Occurrence is limited private;
69 pragma Preelaborable_Initialization (Exception_Occurrence);
71 type Exception_Occurrence_Access is access all Exception_Occurrence;
73 Null_Occurrence : constant Exception_Occurrence;
75 function Exception_Name (Id : Exception_Id) return String;
77 function Exception_Name (X : Exception_Occurrence) return String;
79 function Wide_Exception_Name
80 (Id : Exception_Id) return Wide_String;
81 pragma Ada_05 (Wide_Exception_Name);
83 function Wide_Exception_Name
84 (X : Exception_Occurrence) return Wide_String;
85 pragma Ada_05 (Wide_Exception_Name);
87 function Wide_Wide_Exception_Name
88 (Id : Exception_Id) return Wide_Wide_String;
89 pragma Ada_05 (Wide_Wide_Exception_Name);
91 function Wide_Wide_Exception_Name
92 (X : Exception_Occurrence) return Wide_Wide_String;
93 pragma Ada_05 (Wide_Wide_Exception_Name);
95 procedure Raise_Exception (E : Exception_Id; Message : String := "");
96 pragma No_Return (Raise_Exception);
97 -- Note: In accordance with AI-466, CE is raised if E = Null_Id
99 function Exception_Message (X : Exception_Occurrence) return String;
101 procedure Reraise_Occurrence (X : Exception_Occurrence);
102 -- Note: it would be really nice to give a pragma No_Return for this
103 -- procedure, but it would be wrong, since Reraise_Occurrence does return
104 -- if the argument is the null exception occurrence. See also procedure
105 -- Reraise_Occurrence_Always in the private part of this package.
107 function Exception_Identity (X : Exception_Occurrence) return Exception_Id;
109 function Exception_Information (X : Exception_Occurrence) return String;
110 -- The format of the exception information is as follows:
112 -- exception name (as in Exception_Name)
113 -- message (or a null line if no message)
115 -- 0xyyyyyyyy 0xyyyyyyyy ...
117 -- The lines are separated by a ASCII.LF character
118 -- The nnnn is the partition Id given as decimal digits.
119 -- The 0x... line represents traceback program counter locations,
120 -- in order with the first one being the exception location.
122 -- Note on ordering: the compiler uses the Save_Occurrence procedure, but
123 -- not the function from Rtsfind, so it is important that the procedure
124 -- come first, since Rtsfind finds the first matching entity.
126 procedure Save_Occurrence
127 (Target : out Exception_Occurrence;
128 Source : Exception_Occurrence);
130 function Save_Occurrence
131 (Source : Exception_Occurrence)
132 return Exception_Occurrence_Access;
134 -- Ada 2005 (AI-438): The language revision introduces the following
135 -- subprograms and attribute definitions. We do not provide them
136 -- explicitly. instead, the corresponding stream attributes are made
137 -- available through a pragma Stream_Convert in the private part.
139 -- procedure Read_Exception_Occurrence
140 -- (Stream : not null access Ada.Streams.Root_Stream_Type'Class;
141 -- Item : out Exception_Occurrence);
143 -- procedure Write_Exception_Occurrence
144 -- (Stream : not null access Ada.Streams.Root_Stream_Type'Class;
145 -- Item : Exception_Occurrence);
147 -- for Exception_Occurrence'Read use Read_Exception_Occurrence;
148 -- for Exception_Occurrence'Write use Write_Exception_Occurrence;
151 package SSL renames System.Standard_Library;
152 package SP renames System.Parameters;
154 subtype EOA is Exception_Occurrence_Access;
156 Exception_Msg_Max_Length : constant := SP.Default_Exception_Msg_Max_Length;
162 subtype Code_Loc is System.Address;
163 -- Code location used in building exception tables and for call addresses
164 -- when propagating an exception. Values of this type are created by using
165 -- Label'Address or extracted from machine states using Get_Code_Loc.
167 Null_Loc : constant Code_Loc := System.Null_Address;
168 -- Null code location, used to flag outer level frame
170 type Exception_Id is new SSL.Exception_Data_Ptr;
172 function EId_To_String (X : Exception_Id) return String;
173 function String_To_EId (S : String) return Exception_Id;
174 pragma Stream_Convert (Exception_Id, String_To_EId, EId_To_String);
175 -- Functions for implementing Exception_Id stream attributes
177 Null_Id : constant Exception_Id := null;
179 -------------------------
180 -- Private Subprograms --
181 -------------------------
183 function Current_Target_Exception return Exception_Occurrence;
185 (Ada, Current_Target_Exception,
186 "__gnat_current_target_exception");
187 -- This routine should return the current raised exception on targets
188 -- which have built-in exception handling such as the Java Virtual
189 -- Machine. For other targets this routine is simply ignored. Currently,
190 -- only JGNAT uses this. See 4jexcept.ads for details. The pragma Export
191 -- allows this routine to be accessed elsewhere in the run-time, even
192 -- though it is in the private part of this package (it is not allowed
193 -- to be in the visible part, since this is set by the reference manual).
195 function Exception_Name_Simple (X : Exception_Occurrence) return String;
196 -- Like Exception_Name, but returns the simple non-qualified name of the
197 -- exception. This is used to implement the Exception_Name function in
198 -- Current_Exceptions (the DEC compatible unit). It is called from the
199 -- compiler generated code (using Rtsfind, which does not respect the
200 -- private barrier, so we can place this function in the private part
201 -- where the compiler can find it, but the spec is unchanged.)
203 procedure Raise_Exception_Always (E : Exception_Id; Message : String := "");
204 pragma No_Return (Raise_Exception_Always);
205 pragma Export (Ada, Raise_Exception_Always, "__gnat_raise_exception");
206 -- This differs from Raise_Exception only in that the caller has determined
207 -- that for sure the parameter E is not null, and that therefore no check
208 -- for Null_Id is required. The expander converts Raise_Exception calls to
209 -- Raise_Exception_Always if it can determine this is the case. The Export
210 -- allows this routine to be accessed from Pure units.
212 procedure Raise_From_Signal_Handler
216 (Ada, Raise_From_Signal_Handler,
217 "ada__exceptions__raise_from_signal_handler");
218 pragma No_Return (Raise_From_Signal_Handler);
219 -- This routine is used to raise an exception from a signal handler. The
220 -- signal handler has already stored the machine state (i.e. the state that
221 -- corresponds to the location at which the signal was raised). E is the
222 -- Exception_Id specifying what exception is being raised, and M is a
223 -- pointer to a null-terminated string which is the message to be raised.
224 -- Note that this routine never returns, so it is permissible to simply
225 -- jump to this routine, rather than call it. This may be appropriate for
226 -- systems where the right way to get out of signal handler is to alter the
227 -- PC value in the machine state or in some other way ask the operating
228 -- system to return here rather than to the original location.
230 procedure Raise_From_Controlled_Operation
231 (X : Ada.Exceptions.Exception_Occurrence);
232 pragma No_Return (Raise_From_Controlled_Operation);
233 -- Raise Program_Error, providing information about X (an exception
234 -- raised during a controlled operation) in the exception message.
236 procedure Reraise_Occurrence_Always (X : Exception_Occurrence);
237 pragma No_Return (Reraise_Occurrence_Always);
238 -- This differs from Raise_Occurrence only in that the caller guarantees
239 -- that for sure the parameter X is not the null occurrence, and that
240 -- therefore this procedure cannot return. The expander uses this routine
241 -- in the translation of a raise statement with no parameter (reraise).
243 procedure Reraise_Occurrence_No_Defer (X : Exception_Occurrence);
244 pragma No_Return (Reraise_Occurrence_No_Defer);
245 -- Exactly like Reraise_Occurrence, except that abort is not deferred
246 -- before the call and the parameter X is known not to be the null
247 -- occurrence. This is used in generated code when it is known that
248 -- abort is already deferred.
250 -----------------------
251 -- Polling Interface --
252 -----------------------
254 -- The GNAT compiler has an option to generate polling calls to the Poll
255 -- routine in this package. Specifying the -gnatP option for a compilation
256 -- causes a call to Ada.Exceptions.Poll to be generated on every subprogram
257 -- entry and on every iteration of a loop, thus avoiding the possibility of
258 -- a case of unbounded time between calls.
260 -- This polling interface may be used for instrumentation or debugging
261 -- purposes (e.g. implementing watchpoints in software or in the debugger).
263 -- In the GNAT technology itself, this interface is used to implement
264 -- immediate asynchronous transfer of control and immediate abort on
265 -- targets which do not provide for one thread interrupting another.
267 -- Note: this used to be in a separate unit called System.Poll, but that
268 -- caused horrible circular elaboration problems between System.Poll and
269 -- Ada.Exceptions. One way of solving such circularities is unification!
272 -- Check for asynchronous abort. Note that we do not inline the body.
273 -- This makes the interface more useful for debugging purposes.
275 --------------------------
276 -- Exception_Occurrence --
277 --------------------------
279 package TBE renames System.Traceback_Entries;
281 Max_Tracebacks : constant := 50;
282 -- Maximum number of trace backs stored in exception occurrence
284 type Tracebacks_Array is array (1 .. Max_Tracebacks) of TBE.Traceback_Entry;
285 -- Traceback array stored in exception occurrence
287 type Exception_Occurrence is record
289 -- Exception_Identity for this exception occurrence
290 -- WARNING System.System.Finalization_Implementation.Finalize_List
291 -- relies on the fact that this field is always first in the exception
294 Msg_Length : Natural := 0;
295 -- Length of message (zero = no message)
297 Msg : String (1 .. Exception_Msg_Max_Length);
298 -- Characters of message
300 Cleanup_Flag : Boolean := False;
301 -- The cleanup flag is normally False, it is set True for an exception
302 -- occurrence passed to a cleanup routine, and will still be set True
303 -- when the cleanup routine does a Reraise_Occurrence call using this
304 -- exception occurrence. This is used to avoid recording a bogus trace
305 -- back entry from this reraise call.
307 Exception_Raised : Boolean := False;
308 -- Set to true to indicate that this exception occurrence has actually
309 -- been raised. When an exception occurrence is first created, this is
310 -- set to False, then when it is processed by Raise_Current_Exception,
311 -- it is set to True. If Raise_Current_Exception is used to raise an
312 -- exception for which this flag is already True, then it knows that
313 -- it is dealing with the reraise case (which is useful to distinguish
314 -- for exception tracing purposes).
317 -- Partition_Id for partition raising exception
319 Num_Tracebacks : Natural range 0 .. Max_Tracebacks := 0;
320 -- Number of traceback entries stored
322 Tracebacks : Tracebacks_Array;
323 -- Stored tracebacks (in Tracebacks (1 .. Num_Tracebacks))
325 Private_Data : System.Address := System.Null_Address;
326 -- Field used by low level exception mechanism to store specific data.
327 -- Currently used by the GCC exception mechanism to store a pointer to
328 -- a GNAT_GCC_Exception.
331 function "=" (Left, Right : Exception_Occurrence) return Boolean
333 -- Don't allow comparison on exception occurrences, we should not need
334 -- this, and it would not work right, because of the Msg and Tracebacks
335 -- fields which have unused entries not copied by Save_Occurrence.
337 function EO_To_String (X : Exception_Occurrence) return String;
338 function String_To_EO (S : String) return Exception_Occurrence;
339 pragma Stream_Convert (Exception_Occurrence, String_To_EO, EO_To_String);
340 -- Functions for implementing Exception_Occurrence stream attributes
342 Null_Occurrence : constant Exception_Occurrence := (
345 Msg => (others => ' '),
346 Cleanup_Flag => False,
347 Exception_Raised => False,
350 Tracebacks => (others => TBE.Null_TB_Entry),
351 Private_Data => System.Null_Address);