1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- A D A . E X C E P T I O N S --
9 -- Copyright (C) 1992-2011, 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 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. --
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. --
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/>. --
31 -- GNAT was originally developed by the GNAT team at New York University. --
32 -- Extensive contributions were provided by Ada Core Technologies Inc. --
34 ------------------------------------------------------------------------------
36 -- This version of Ada.Exceptions is a full Ada 95 version. It omits Ada 2005
37 -- features such as the additional definitions of Exception_Name returning
38 -- Wide_[Wide_]String.
40 -- It is used for building the compiler and the basic tools, since these
41 -- builds may be done with bootstrap compilers that cannot handle these
42 -- additions. The full version of Ada.Exceptions can be found in the files
43 -- a-except-2005.ads/adb, and is used for all other builds where full Ada
44 -- 2005 functionality is required. In particular, it is used for building
45 -- run times on all targets.
50 -- We must turn polling off for this unit, because otherwise we get
51 -- elaboration circularities with ourself.
54 with System.Parameters;
55 with System.Standard_Library;
56 with System.Traceback_Entries;
58 package Ada.Exceptions is
59 pragma Warnings (Off);
60 pragma Preelaborate_05;
62 -- We make this preelaborable in Ada 2005 mode. If we did not do this, then
63 -- run time units used by the compiler (e.g. s-soflin.ads) would run
64 -- into trouble. Conformance is not an issue, since this version is used
65 -- only by the compiler.
67 type Exception_Id is private;
69 Null_Id : constant Exception_Id;
71 type Exception_Occurrence is limited private;
73 type Exception_Occurrence_Access is access all Exception_Occurrence;
75 Null_Occurrence : constant Exception_Occurrence;
77 function Exception_Name (X : Exception_Occurrence) return String;
78 -- Same as Exception_Name (Exception_Identity (X))
80 function Exception_Name (Id : Exception_Id) return String;
82 procedure Raise_Exception (E : Exception_Id; Message : String := "");
83 pragma No_Return (Raise_Exception);
84 -- Note: In accordance with AI-466, CE is raised if E = Null_Id
86 function Exception_Message (X : Exception_Occurrence) return String;
88 procedure Reraise_Occurrence (X : Exception_Occurrence);
89 -- Note: it would be really nice to give a pragma No_Return for this
90 -- procedure, but it would be wrong, since Reraise_Occurrence does return
91 -- if the argument is the null exception occurrence. See also procedure
92 -- Reraise_Occurrence_Always in the private part of this package.
94 function Exception_Identity (X : Exception_Occurrence) return Exception_Id;
96 function Exception_Information (X : Exception_Occurrence) return String;
97 -- The format of the exception information is as follows:
99 -- exception name (as in Exception_Name)
100 -- message (or a null line if no message)
102 -- 0xyyyyyyyy 0xyyyyyyyy ...
104 -- The lines are separated by a ASCII.LF character
105 -- The nnnn is the partition Id given as decimal digits.
106 -- The 0x... line represents traceback program counter locations,
107 -- in order with the first one being the exception location.
109 -- Note on ordering: the compiler uses the Save_Occurrence procedure, but
110 -- not the function from Rtsfind, so it is important that the procedure
111 -- come first, since Rtsfind finds the first matching entity.
113 procedure Save_Occurrence
114 (Target : out Exception_Occurrence;
115 Source : Exception_Occurrence);
117 function Save_Occurrence
118 (Source : Exception_Occurrence)
119 return Exception_Occurrence_Access;
122 package SSL renames System.Standard_Library;
123 package SP renames System.Parameters;
125 subtype EOA is Exception_Occurrence_Access;
127 Exception_Msg_Max_Length : constant := SP.Default_Exception_Msg_Max_Length;
133 subtype Code_Loc is System.Address;
134 -- Code location used in building exception tables and for call addresses
135 -- when propagating an exception. Values of this type are created by using
136 -- Label'Address or extracted from machine states using Get_Code_Loc.
138 Null_Loc : constant Code_Loc := System.Null_Address;
139 -- Null code location, used to flag outer level frame
141 type Exception_Id is new SSL.Exception_Data_Ptr;
143 function EId_To_String (X : Exception_Id) return String;
144 function String_To_EId (S : String) return Exception_Id;
145 pragma Stream_Convert (Exception_Id, String_To_EId, EId_To_String);
146 -- Functions for implementing Exception_Id stream attributes
148 Null_Id : constant Exception_Id := null;
150 -------------------------
151 -- Private Subprograms --
152 -------------------------
154 function Current_Target_Exception return Exception_Occurrence;
156 (Ada, Current_Target_Exception,
157 "__gnat_current_target_exception");
158 -- This routine should return the current raised exception on targets
159 -- which have built-in exception handling such as the Java Virtual
160 -- Machine. For other targets this routine is simply ignored. Currently,
161 -- only JGNAT uses this. See 4jexcept.ads for details. The pragma Export
162 -- allows this routine to be accessed elsewhere in the run-time, even
163 -- though it is in the private part of this package (it is not allowed
164 -- to be in the visible part, since this is set by the reference manual).
166 function Exception_Name_Simple (X : Exception_Occurrence) return String;
167 -- Like Exception_Name, but returns the simple non-qualified name of the
168 -- exception. This is used to implement the Exception_Name function in
169 -- Current_Exceptions (the DEC compatible unit). It is called from the
170 -- compiler generated code (using Rtsfind, which does not respect the
171 -- private barrier, so we can place this function in the private part
172 -- where the compiler can find it, but the spec is unchanged.)
174 procedure Raise_Exception_Always (E : Exception_Id; Message : String := "");
175 pragma No_Return (Raise_Exception_Always);
176 pragma Export (Ada, Raise_Exception_Always, "__gnat_raise_exception");
177 -- This differs from Raise_Exception only in that the caller has determined
178 -- that for sure the parameter E is not null, and that therefore no check
179 -- for Null_Id is required. The expander converts Raise_Exception calls to
180 -- Raise_Exception_Always if it can determine this is the case. The Export
181 -- allows this routine to be accessed from Pure units.
183 procedure Raise_From_Signal_Handler
187 (Ada, Raise_From_Signal_Handler,
188 "ada__exceptions__raise_from_signal_handler");
189 pragma No_Return (Raise_From_Signal_Handler);
190 -- This routine is used to raise an exception from a signal handler. The
191 -- signal handler has already stored the machine state (i.e. the state that
192 -- corresponds to the location at which the signal was raised). E is the
193 -- Exception_Id specifying what exception is being raised, and M is a
194 -- pointer to a null-terminated string which is the message to be raised.
195 -- Note that this routine never returns, so it is permissible to simply
196 -- jump to this routine, rather than call it. This may be appropriate for
197 -- systems where the right way to get out of signal handler is to alter the
198 -- PC value in the machine state or in some other way ask the operating
199 -- system to return here rather than to the original location.
201 procedure Raise_From_Controlled_Operation
202 (X : Ada.Exceptions.Exception_Occurrence);
203 pragma No_Return (Raise_From_Controlled_Operation);
205 (Ada, Raise_From_Controlled_Operation,
206 "__gnat_raise_from_controlled_operation");
207 -- Raise Program_Error, providing information about X (an exception raised
208 -- during a controlled operation) in the exception message.
210 procedure Reraise_Occurrence_Always (X : Exception_Occurrence);
211 pragma No_Return (Reraise_Occurrence_Always);
212 -- This differs from Raise_Occurrence only in that the caller guarantees
213 -- that for sure the parameter X is not the null occurrence, and that
214 -- therefore this procedure cannot return. The expander uses this routine
215 -- in the translation of a raise statement with no parameter (reraise).
217 procedure Reraise_Occurrence_No_Defer (X : Exception_Occurrence);
218 pragma No_Return (Reraise_Occurrence_No_Defer);
219 -- Exactly like Reraise_Occurrence, except that abort is not deferred
220 -- before the call and the parameter X is known not to be the null
221 -- occurrence. This is used in generated code when it is known that
222 -- abort is already deferred.
224 function Triggered_By_Abort return Boolean;
225 -- Determine whether the current exception (if it exists) is an instance of
226 -- Standard'Abort_Signal.
228 -----------------------
229 -- Polling Interface --
230 -----------------------
232 -- The GNAT compiler has an option to generate polling calls to the Poll
233 -- routine in this package. Specifying the -gnatP option for a compilation
234 -- causes a call to Ada.Exceptions.Poll to be generated on every subprogram
235 -- entry and on every iteration of a loop, thus avoiding the possibility of
236 -- a case of unbounded time between calls.
238 -- This polling interface may be used for instrumentation or debugging
239 -- purposes (e.g. implementing watchpoints in software or in the debugger).
241 -- In the GNAT technology itself, this interface is used to implement
242 -- immediate asynchronous transfer of control and immediate abort on
243 -- targets which do not provide for one thread interrupting another.
245 -- Note: this used to be in a separate unit called System.Poll, but that
246 -- caused horrible circular elaboration problems between System.Poll and
247 -- Ada.Exceptions. One way of solving such circularities is unification!
250 -- Check for asynchronous abort. Note that we do not inline the body.
251 -- This makes the interface more useful for debugging purposes.
253 --------------------------
254 -- Exception_Occurrence --
255 --------------------------
257 package TBE renames System.Traceback_Entries;
259 Max_Tracebacks : constant := 50;
260 -- Maximum number of trace backs stored in exception occurrence
262 type Tracebacks_Array is array (1 .. Max_Tracebacks) of TBE.Traceback_Entry;
263 -- Traceback array stored in exception occurrence
265 type Exception_Occurrence is record
267 -- Exception_Identity for this exception occurrence
268 -- WARNING System.System.Finalization_Implementation.Finalize_List
269 -- relies on the fact that this field is always first in the exception
272 Msg_Length : Natural := 0;
273 -- Length of message (zero = no message)
275 Msg : String (1 .. Exception_Msg_Max_Length);
276 -- Characters of message
278 Exception_Raised : Boolean := False;
279 -- Set to true to indicate that this exception occurrence has actually
280 -- been raised. When an exception occurrence is first created, this is
281 -- set to False, then when it is processed by Raise_Current_Exception,
282 -- it is set to True. If Raise_Current_Exception is used to raise an
283 -- exception for which this flag is already True, then it knows that
284 -- it is dealing with the reraise case (which is useful to distinguish
285 -- for exception tracing purposes).
288 -- Partition_Id for partition raising exception
290 Num_Tracebacks : Natural range 0 .. Max_Tracebacks := 0;
291 -- Number of traceback entries stored
293 Tracebacks : Tracebacks_Array;
294 -- Stored tracebacks (in Tracebacks (1 .. Num_Tracebacks))
297 function "=" (Left, Right : Exception_Occurrence) return Boolean
299 -- Don't allow comparison on exception occurrences, we should not need
300 -- this, and it would not work right, because of the Msg and Tracebacks
301 -- fields which have unused entries not copied by Save_Occurrence.
303 function EO_To_String (X : Exception_Occurrence) return String;
304 function String_To_EO (S : String) return Exception_Occurrence;
305 pragma Stream_Convert (Exception_Occurrence, String_To_EO, EO_To_String);
306 -- Functions for implementing Exception_Occurrence stream attributes
308 Null_Occurrence : constant Exception_Occurrence := (
311 Msg => (others => ' '),
312 Exception_Raised => False,
315 Tracebacks => (others => TBE.Null_TB_Entry));