1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- A D A . E X C E P T I O N S --
9 -- Copyright (C) 1992-2007, 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 is used for all Ada 2005 builds. It differs from a-except.ads
39 -- only with respect to the addition of Wide_[Wide]Exception_Name functions.
40 -- The additional entities are marked with pragma Ada_05, so this extended
41 -- unit is also perfectly suitable for use in Ada 95 or Ada 83 mode.
43 -- The reason for this splitting off of a separate version is that bootstrap
44 -- compilers often will be used that do not support Ada 2005 features, and
45 -- Ada.Exceptions is part of the compiler sources.
47 -- The base version of this unit Ada.Exceptions omits the Wide version of
48 -- Exception_Name and is used to build the compiler and other basic tools.
51 -- We must turn polling off for this unit, because otherwise we get
52 -- elaboration circularities with ourself.
55 with System
.Parameters
;
56 with System
.Standard_Library
;
57 with System
.Traceback_Entries
;
59 package Ada
.Exceptions
is
60 pragma Warnings
(Off
);
61 pragma Preelaborate_05
;
63 -- In accordance with Ada 2005 AI-362. The warnings pragmas are so that we
64 -- can compile this using older compiler versions, which will ignore the
65 -- pragma, which is fine for the bootstrap.
67 type Exception_Id
is private;
68 pragma Preelaborable_Initialization
(Exception_Id
);
70 Null_Id
: constant Exception_Id
;
72 type Exception_Occurrence
is limited private;
73 pragma Preelaborable_Initialization
(Exception_Occurrence
);
75 type Exception_Occurrence_Access
is access all Exception_Occurrence
;
77 Null_Occurrence
: constant Exception_Occurrence
;
79 function Exception_Name
(Id
: Exception_Id
) return String;
81 function Exception_Name
(X
: Exception_Occurrence
) return String;
83 function Wide_Exception_Name
84 (Id
: Exception_Id
) return Wide_String;
85 pragma Ada_05
(Wide_Exception_Name
);
87 function Wide_Exception_Name
88 (X
: Exception_Occurrence
) return Wide_String;
89 pragma Ada_05
(Wide_Exception_Name
);
91 function Wide_Wide_Exception_Name
92 (Id
: Exception_Id
) return Wide_Wide_String
;
93 pragma Ada_05
(Wide_Wide_Exception_Name
);
95 function Wide_Wide_Exception_Name
96 (X
: Exception_Occurrence
) return Wide_Wide_String
;
97 pragma Ada_05
(Wide_Wide_Exception_Name
);
99 procedure Raise_Exception
(E
: Exception_Id
; Message
: String := "");
100 -- Note: it would be really nice to give a pragma No_Return for this
101 -- procedure, but it would be wrong, since Raise_Exception does return
102 -- if given the null exception. However we do special case the name in
103 -- the test in the compiler for issuing a warning for a missing return
104 -- after this call. Program_Error seems reasonable enough in such a case.
105 -- See also the routine Raise_Exception_Always in the private part.
107 function Exception_Message
(X
: Exception_Occurrence
) return String;
109 procedure Reraise_Occurrence
(X
: Exception_Occurrence
);
110 -- Note: it would be really nice to give a pragma No_Return for this
111 -- procedure, but it would be wrong, since Reraise_Occurrence does return
112 -- if the argument is the null exception occurrence. See also procedure
113 -- Reraise_Occurrence_Always in the private part of this package.
115 function Exception_Identity
(X
: Exception_Occurrence
) return Exception_Id
;
117 function Exception_Information
(X
: Exception_Occurrence
) return String;
118 -- The format of the exception information is as follows:
120 -- exception name (as in Exception_Name)
121 -- message (or a null line if no message)
123 -- 0xyyyyyyyy 0xyyyyyyyy ...
125 -- The lines are separated by a ASCII.LF character
126 -- The nnnn is the partition Id given as decimal digits.
127 -- The 0x... line represents traceback program counter locations,
128 -- in order with the first one being the exception location.
130 -- Note on ordering: the compiler uses the Save_Occurrence procedure, but
131 -- not the function from Rtsfind, so it is important that the procedure
132 -- come first, since Rtsfind finds the first matching entity.
134 procedure Save_Occurrence
135 (Target
: out Exception_Occurrence
;
136 Source
: Exception_Occurrence
);
138 function Save_Occurrence
139 (Source
: Exception_Occurrence
)
140 return Exception_Occurrence_Access
;
142 -- Ada 2005 (AI-438): The language revision introduces the
143 -- following subprograms and attribute definitions. We do not
144 -- provide them explicitly; instead, the corresponding stream
145 -- attributes are made available through a pragma Stream_Convert
146 -- in the private part of this package.
148 -- procedure Read_Exception_Occurrence
149 -- (Stream : not null access Ada.Streams.Root_Stream_Type'Class;
150 -- Item : out Exception_Occurrence);
152 -- procedure Write_Exception_Occurrence
153 -- (Stream : not null access Ada.Streams.Root_Stream_Type'Class;
154 -- Item : Exception_Occurrence);
156 -- for Exception_Occurrence'Read use Read_Exception_Occurrence;
157 -- for Exception_Occurrence'Write use Write_Exception_Occurrence;
160 package SSL
renames System
.Standard_Library
;
161 package SP
renames System
.Parameters
;
163 subtype EOA
is Exception_Occurrence_Access
;
165 Exception_Msg_Max_Length
: constant := SP
.Default_Exception_Msg_Max_Length
;
171 subtype Code_Loc
is System
.Address
;
172 -- Code location used in building exception tables and for call addresses
173 -- when propagating an exception. Values of this type are created by using
174 -- Label'Address or extracted from machine states using Get_Code_Loc.
176 Null_Loc
: constant Code_Loc
:= System
.Null_Address
;
177 -- Null code location, used to flag outer level frame
179 type Exception_Id
is new SSL
.Exception_Data_Ptr
;
181 function EId_To_String
(X
: Exception_Id
) return String;
182 function String_To_EId
(S
: String) return Exception_Id
;
183 pragma Stream_Convert
(Exception_Id
, String_To_EId
, EId_To_String
);
184 -- Functions for implementing Exception_Id stream attributes
186 Null_Id
: constant Exception_Id
:= null;
188 -------------------------
189 -- Private Subprograms --
190 -------------------------
192 function Current_Target_Exception
return Exception_Occurrence
;
194 (Ada
, Current_Target_Exception
,
195 "__gnat_current_target_exception");
196 -- This routine should return the current raised exception on targets
197 -- which have built-in exception handling such as the Java Virtual
198 -- Machine. For other targets this routine is simply ignored. Currently,
199 -- only JGNAT uses this. See 4jexcept.ads for details. The pragma Export
200 -- allows this routine to be accessed elsewhere in the run-time, even
201 -- though it is in the private part of this package (it is not allowed
202 -- to be in the visible part, since this is set by the reference manual).
204 function Exception_Name_Simple
(X
: Exception_Occurrence
) return String;
205 -- Like Exception_Name, but returns the simple non-qualified name of the
206 -- exception. This is used to implement the Exception_Name function in
207 -- Current_Exceptions (the DEC compatible unit). It is called from the
208 -- compiler generated code (using Rtsfind, which does not respect the
209 -- private barrier, so we can place this function in the private part
210 -- where the compiler can find it, but the spec is unchanged.)
212 procedure Raise_Exception_Always
(E
: Exception_Id
; Message
: String := "");
213 pragma No_Return
(Raise_Exception_Always
);
214 pragma Export
(Ada
, Raise_Exception_Always
, "__gnat_raise_exception");
215 -- This differs from Raise_Exception only in that the caller has determined
216 -- that for sure the parameter E is not null, and that therefore the call
217 -- to this procedure cannot return. The expander converts Raise_Exception
218 -- calls to Raise_Exception_Always if it can determine this is the case.
219 -- The Export allows this routine to be accessed from Pure units.
221 procedure Raise_From_Signal_Handler
225 (Ada
, Raise_From_Signal_Handler
,
226 "ada__exceptions__raise_from_signal_handler");
227 pragma No_Return
(Raise_From_Signal_Handler
);
228 -- This routine is used to raise an exception from a signal handler. The
229 -- signal handler has already stored the machine state (i.e. the state that
230 -- corresponds to the location at which the signal was raised). E is the
231 -- Exception_Id specifying what exception is being raised, and M is a
232 -- pointer to a null-terminated string which is the message to be raised.
233 -- Note that this routine never returns, so it is permissible to simply
234 -- jump to this routine, rather than call it. This may be appropriate for
235 -- systems where the right way to get out of signal handler is to alter the
236 -- PC value in the machine state or in some other way ask the operating
237 -- system to return here rather than to the original location.
239 procedure Raise_From_Controlled_Operation
240 (X
: Ada
.Exceptions
.Exception_Occurrence
);
241 pragma No_Return
(Raise_From_Controlled_Operation
);
242 -- Raise Program_Error, proviving information about X (an exception
243 -- raised during a controlled operation) in the exception message.
245 procedure Reraise_Occurrence_Always
(X
: Exception_Occurrence
);
246 pragma No_Return
(Reraise_Occurrence_Always
);
247 -- This differs from Raise_Occurrence only in that the caller guarantees
248 -- that for sure the parameter X is not the null occurrence, and that
249 -- therefore this procedure cannot return. The expander uses this routine
250 -- in the translation of a raise statement with no parameter (reraise).
252 procedure Reraise_Occurrence_No_Defer
(X
: Exception_Occurrence
);
253 pragma No_Return
(Reraise_Occurrence_No_Defer
);
254 -- Exactly like Reraise_Occurrence, except that abort is not deferred
255 -- before the call and the parameter X is known not to be the null
256 -- occurrence. This is used in generated code when it is known that
257 -- abort is already deferred.
259 -----------------------
260 -- Polling Interface --
261 -----------------------
263 -- The GNAT compiler has an option to generate polling calls to the Poll
264 -- routine in this package. Specifying the -gnatP option for a compilation
265 -- causes a call to Ada.Exceptions.Poll to be generated on every subprogram
266 -- entry and on every iteration of a loop, thus avoiding the possibility of
267 -- a case of unbounded time between calls.
269 -- This polling interface may be used for instrumentation or debugging
270 -- purposes (e.g. implementing watchpoints in software or in the debugger).
272 -- In the GNAT technology itself, this interface is used to implement
273 -- immediate aynschronous transfer of control and immediate abort on
274 -- targets which do not provide for one thread interrupting another.
276 -- Note: this used to be in a separate unit called System.Poll, but that
277 -- caused horrible circular elaboration problems between System.Poll and
278 -- Ada.Exceptions. One way of solving such circularities is unification!
281 -- Check for asynchronous abort. Note that we do not inline the body.
282 -- This makes the interface more useful for debugging purposes.
284 --------------------------
285 -- Exception_Occurrence --
286 --------------------------
288 package TBE
renames System
.Traceback_Entries
;
290 Max_Tracebacks
: constant := 50;
291 -- Maximum number of trace backs stored in exception occurrence
293 type Tracebacks_Array
is array (1 .. Max_Tracebacks
) of TBE
.Traceback_Entry
;
294 -- Traceback array stored in exception occurrence
296 type Exception_Occurrence
is record
298 -- Exception_Identity for this exception occurrence
299 -- WARNING System.System.Finalization_Implementation.Finalize_List
300 -- relies on the fact that this field is always first in the exception
303 Msg_Length
: Natural := 0;
304 -- Length of message (zero = no message)
306 Msg
: String (1 .. Exception_Msg_Max_Length
);
307 -- Characters of message
309 Cleanup_Flag
: Boolean := False;
310 -- The cleanup flag is normally False, it is set True for an exception
311 -- occurrence passed to a cleanup routine, and will still be set True
312 -- when the cleanup routine does a Reraise_Occurrence call using this
313 -- exception occurrence. This is used to avoid recording a bogus trace
314 -- back entry from this reraise call.
316 Exception_Raised
: Boolean := False;
317 -- Set to true to indicate that this exception occurrence has actually
318 -- been raised. When an exception occurrence is first created, this is
319 -- set to False, then when it is processed by Raise_Current_Exception,
320 -- it is set to True. If Raise_Current_Exception is used to raise an
321 -- exception for which this flag is already True, then it knows that
322 -- it is dealing with the reraise case (which is useful to distinguish
323 -- for exception tracing purposes).
326 -- Partition_Id for partition raising exception
328 Num_Tracebacks
: Natural range 0 .. Max_Tracebacks
:= 0;
329 -- Number of traceback entries stored
331 Tracebacks
: Tracebacks_Array
;
332 -- Stored tracebacks (in Tracebacks (1 .. Num_Tracebacks))
334 Private_Data
: System
.Address
:= System
.Null_Address
;
335 -- Field used by low level exception mechanism to store specific data.
336 -- Currently used by the GCC exception mechanism to store a pointer to
337 -- a GNAT_GCC_Exception.
340 function "=" (Left
, Right
: Exception_Occurrence
) return Boolean
342 -- Don't allow comparison on exception occurrences, we should not need
343 -- this, and it would not work right, because of the Msg and Tracebacks
344 -- fields which have unused entries not copied by Save_Occurrence.
346 function EO_To_String
(X
: Exception_Occurrence
) return String;
347 function String_To_EO
(S
: String) return Exception_Occurrence
;
348 pragma Stream_Convert
(Exception_Occurrence
, String_To_EO
, EO_To_String
);
349 -- Functions for implementing Exception_Occurrence stream attributes
351 Null_Occurrence
: constant Exception_Occurrence
:= (
354 Msg
=> (others => ' '),
355 Cleanup_Flag
=> False,
356 Exception_Raised
=> False,
359 Tracebacks
=> (others => TBE
.Null_TB_Entry
),
360 Private_Data
=> System
.Null_Address
);