1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- A D A . E X C E P T I O N S --
9 -- Copyright (C) 1992-2006, 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 is a full Ada 95 version.
39 -- It is used for building the compiler and the basic tools, since these
40 -- builds may be done with bootstrap compilers that cannot handle these
41 -- additions. The full version of Ada.Exceptions can be found in the files
42 -- a-except-2005.ads/adb, and is used for all other builds where full Ada
43 -- 2005 functionality is required. in particular, it is used for building
44 -- run times on all targets.
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 -- We make this preelaborable in Ada 2005 mode. If we did not do this, then
60 -- run time units used by the compiler (e.g. s-soflin.ads) would run
61 -- into trouble. Conformance is not an issue, since this version is used
62 -- only by the compiler.
64 type Exception_Id
is private;
66 Null_Id
: constant Exception_Id
;
68 type Exception_Occurrence
is limited private;
70 type Exception_Occurrence_Access
is access all Exception_Occurrence
;
72 Null_Occurrence
: constant Exception_Occurrence
;
74 function Exception_Name
(X
: Exception_Occurrence
) return String;
75 -- Same as Exception_Name (Exception_Identity (X))
77 function Exception_Name
(Id
: Exception_Id
) return String;
79 procedure Raise_Exception
(E
: Exception_Id
; Message
: String := "");
80 -- Note: it would be really nice to give a pragma No_Return for this
81 -- procedure, but it would be wrong, since Raise_Exception does return if
82 -- given the null exception in Ada 95 mode. However we do special case the
83 -- name in the test in the compiler for issuing a warning for a missing
84 -- return after this call. Program_Error seems reasonable enough in such a
85 -- case. See also the routine Raise_Exception_Always in the private part.
87 function Exception_Message
(X
: Exception_Occurrence
) return String;
89 procedure Reraise_Occurrence
(X
: Exception_Occurrence
);
90 -- Note: it would be really nice to give a pragma No_Return for this
91 -- procedure, but it would be wrong, since Reraise_Occurrence does return
92 -- if the argument is the null exception occurrence. See also procedure
93 -- Reraise_Occurrence_Always in the private part of this package.
95 function Exception_Identity
(X
: Exception_Occurrence
) return Exception_Id
;
97 function Exception_Information
(X
: Exception_Occurrence
) return String;
98 -- The format of the exception information is as follows:
100 -- exception name (as in Exception_Name)
101 -- message (or a null line if no message)
103 -- 0xyyyyyyyy 0xyyyyyyyy ...
105 -- The lines are separated by a ASCII.LF character
106 -- The nnnn is the partition Id given as decimal digits.
107 -- The 0x... line represents traceback program counter locations,
108 -- in order with the first one being the exception location.
110 -- Note on ordering: the compiler uses the Save_Occurrence procedure, but
111 -- not the function from Rtsfind, so it is important that the procedure
112 -- come first, since Rtsfind finds the first matching entity.
114 procedure Save_Occurrence
115 (Target
: out Exception_Occurrence
;
116 Source
: Exception_Occurrence
);
118 function Save_Occurrence
119 (Source
: Exception_Occurrence
)
120 return Exception_Occurrence_Access
;
123 package SSL
renames System
.Standard_Library
;
124 package SP
renames System
.Parameters
;
126 subtype EOA
is Exception_Occurrence_Access
;
128 Exception_Msg_Max_Length
: constant := SP
.Default_Exception_Msg_Max_Length
;
134 subtype Code_Loc
is System
.Address
;
135 -- Code location used in building exception tables and for call addresses
136 -- when propagating an exception. Values of this type are created by using
137 -- Label'Address or extracted from machine states using Get_Code_Loc.
139 Null_Loc
: constant Code_Loc
:= System
.Null_Address
;
140 -- Null code location, used to flag outer level frame
142 type Exception_Id
is new SSL
.Exception_Data_Ptr
;
144 function EId_To_String
(X
: Exception_Id
) return String;
145 function String_To_EId
(S
: String) return Exception_Id
;
146 pragma Stream_Convert
(Exception_Id
, String_To_EId
, EId_To_String
);
147 -- Functions for implementing Exception_Id stream attributes
149 Null_Id
: constant Exception_Id
:= null;
151 -------------------------
152 -- Private Subprograms --
153 -------------------------
155 function Current_Target_Exception
return Exception_Occurrence
;
157 (Ada
, Current_Target_Exception
,
158 "__gnat_current_target_exception");
159 -- This routine should return the current raised exception on targets
160 -- which have built-in exception handling such as the Java Virtual
161 -- Machine. For other targets this routine is simply ignored. Currently,
162 -- only JGNAT uses this. See 4jexcept.ads for details. The pragma Export
163 -- allows this routine to be accessed elsewhere in the run-time, even
164 -- though it is in the private part of this package (it is not allowed
165 -- to be in the visible part, since this is set by the reference manual).
167 function Exception_Name_Simple
(X
: Exception_Occurrence
) return String;
168 -- Like Exception_Name, but returns the simple non-qualified name of the
169 -- exception. This is used to implement the Exception_Name function in
170 -- Current_Exceptions (the DEC compatible unit). It is called from the
171 -- compiler generated code (using Rtsfind, which does not respect the
172 -- private barrier, so we can place this function in the private part
173 -- where the compiler can find it, but the spec is unchanged.)
175 procedure Raise_Exception_Always
(E
: Exception_Id
; Message
: String := "");
176 pragma No_Return
(Raise_Exception_Always
);
177 pragma Export
(Ada
, Raise_Exception_Always
, "__gnat_raise_exception");
178 -- This differs from Raise_Exception only in that the caller has determined
179 -- that for sure the parameter E is not null, and that therefore the call
180 -- to this procedure cannot return. The expander converts Raise_Exception
181 -- calls to Raise_Exception_Always if it can determine this is the case.
182 -- The Export allows this routine to be accessed from Pure units.
184 procedure Raise_From_Signal_Handler
188 (Ada
, Raise_From_Signal_Handler
,
189 "ada__exceptions__raise_from_signal_handler");
190 pragma No_Return
(Raise_From_Signal_Handler
);
191 -- This routine is used to raise an exception from a signal handler. The
192 -- signal handler has already stored the machine state (i.e. the state that
193 -- corresponds to the location at which the signal was raised). E is the
194 -- Exception_Id specifying what exception is being raised, and M is a
195 -- pointer to a null-terminated string which is the message to be raised.
196 -- Note that this routine never returns, so it is permissible to simply
197 -- jump to this routine, rather than call it. This may be appropriate for
198 -- systems where the right way to get out of signal handler is to alter the
199 -- PC value in the machine state or in some other way ask the operating
200 -- system to return here rather than to the original location.
202 procedure Reraise_Occurrence_Always
(X
: Exception_Occurrence
);
203 pragma No_Return
(Reraise_Occurrence_Always
);
204 -- This differs from Raise_Occurrence only in that the caller guarantees
205 -- that for sure the parameter X is not the null occurrence, and that
206 -- therefore this procedure cannot return. The expander uses this routine
207 -- in the translation of a raise statement with no parameter (reraise).
209 procedure Reraise_Occurrence_No_Defer
(X
: Exception_Occurrence
);
210 pragma No_Return
(Reraise_Occurrence_No_Defer
);
211 -- Exactly like Reraise_Occurrence, except that abort is not deferred
212 -- before the call and the parameter X is known not to be the null
213 -- occurrence. This is used in generated code when it is known that
214 -- abort is already deferred.
216 -----------------------
217 -- Polling Interface --
218 -----------------------
220 -- The GNAT compiler has an option to generate polling calls to the Poll
221 -- routine in this package. Specifying the -gnatP option for a compilation
222 -- causes a call to Ada.Exceptions.Poll to be generated on every subprogram
223 -- entry and on every iteration of a loop, thus avoiding the possibility of
224 -- a case of unbounded time between calls.
226 -- This polling interface may be used for instrumentation or debugging
227 -- purposes (e.g. implementing watchpoints in software or in the debugger).
229 -- In the GNAT technology itself, this interface is used to implement
230 -- immediate aynschronous transfer of control and immediate abort on
231 -- targets which do not provide for one thread interrupting another.
233 -- Note: this used to be in a separate unit called System.Poll, but that
234 -- caused horrible circular elaboration problems between System.Poll and
235 -- Ada.Exceptions. One way of solving such circularities is unification!
238 -- Check for asynchronous abort. Note that we do not inline the body.
239 -- This makes the interface more useful for debugging purposes.
241 --------------------------
242 -- Exception_Occurrence --
243 --------------------------
245 package TBE
renames System
.Traceback_Entries
;
247 Max_Tracebacks
: constant := 50;
248 -- Maximum number of trace backs stored in exception occurrence
250 type Tracebacks_Array
is array (1 .. Max_Tracebacks
) of TBE
.Traceback_Entry
;
251 -- Traceback array stored in exception occurrence
253 type Exception_Occurrence
is record
255 -- Exception_Identity for this exception occurrence
256 -- WARNING System.System.Finalization_Implementation.Finalize_List
257 -- relies on the fact that this field is always first in the exception
260 Msg_Length
: Natural := 0;
261 -- Length of message (zero = no message)
263 Msg
: String (1 .. Exception_Msg_Max_Length
);
264 -- Characters of message
266 Cleanup_Flag
: Boolean := False;
267 -- The cleanup flag is normally False, it is set True for an exception
268 -- occurrence passed to a cleanup routine, and will still be set True
269 -- when the cleanup routine does a Reraise_Occurrence call using this
270 -- exception occurrence. This is used to avoid recording a bogus trace
271 -- back entry from this reraise call.
273 Exception_Raised
: Boolean := False;
274 -- Set to true to indicate that this exception occurrence has actually
275 -- been raised. When an exception occurrence is first created, this is
276 -- set to False, then when it is processed by Raise_Current_Exception,
277 -- it is set to True. If Raise_Current_Exception is used to raise an
278 -- exception for which this flag is already True, then it knows that
279 -- it is dealing with the reraise case (which is useful to distinguish
280 -- for exception tracing purposes).
283 -- Partition_Id for partition raising exception
285 Num_Tracebacks
: Natural range 0 .. Max_Tracebacks
:= 0;
286 -- Number of traceback entries stored
288 Tracebacks
: Tracebacks_Array
;
289 -- Stored tracebacks (in Tracebacks (1 .. Num_Tracebacks))
291 Private_Data
: System
.Address
:= System
.Null_Address
;
292 -- Field used by low level exception mechanism to store specific data.
293 -- Currently used by the GCC exception mechanism to store a pointer to
294 -- a GNAT_GCC_Exception.
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 Cleanup_Flag
=> False,
313 Exception_Raised
=> False,
316 Tracebacks
=> (others => TBE
.Null_TB_Entry
),
317 Private_Data
=> System
.Null_Address
);