gcc/ada/a-exexpr-gcc.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --  A D A . E X C E P T I O N S . E X C E P T I O N _ P R O P A G A T I O N --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2013, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 --  This is the version using the GCC EH mechanism
  33
  34 with Ada.Unchecked_Conversion;
  35 with Ada.Unchecked_Deallocation;
  36
  37 with System.Storage_Elements;   use System.Storage_Elements;
  38 with System.Exceptions.Machine; use System.Exceptions.Machine;
  39
  40 separate (Ada.Exceptions)
  41 package body Exception_Propagation is
  42
  43    use Exception_Traces;
  44
  45    Foreign_Exception : aliased System.Standard_Library.Exception_Data;
  46    pragma Import (Ada, Foreign_Exception,
  47                   "system__exceptions__foreign_exception");
  48    --  Id for foreign exceptions
  49
  50    --------------------------------------------------------------
  51    -- GNAT Specific Entities To Deal With The GCC EH Circuitry --
  52    --------------------------------------------------------------
  53
  54    procedure GNAT_GCC_Exception_Cleanup
  55      (Reason : Unwind_Reason_Code;
  56       Excep  : not null GNAT_GCC_Exception_Access);
  57    pragma Convention (C, GNAT_GCC_Exception_Cleanup);
  58    --  Procedure called when a GNAT GCC exception is free.
  59
  60    procedure Propagate_GCC_Exception
  61      (GCC_Exception : not null GCC_Exception_Access);
  62    pragma No_Return (Propagate_GCC_Exception);
  63    --  Propagate a GCC exception
  64
  65    procedure Reraise_GCC_Exception
  66      (GCC_Exception : not null GCC_Exception_Access);
  67    pragma No_Return (Reraise_GCC_Exception);
  68    pragma Export (C, Reraise_GCC_Exception, "__gnat_reraise_zcx");
  69    --  Called to implement raise without exception, ie reraise. Called
  70    --  directly from gigi.
  71
  72    function Setup_Current_Excep
  73      (GCC_Exception : not null GCC_Exception_Access) return EOA;
  74    pragma Export (C, Setup_Current_Excep, "__gnat_setup_current_excep");
  75    --  Write Get_Current_Excep.all from GCC_Exception. Called by the
  76    --  personality routine.
  77
  78    procedure Unhandled_Except_Handler
  79      (GCC_Exception : not null GCC_Exception_Access);
  80    pragma No_Return (Unhandled_Except_Handler);
  81    pragma Export (C, Unhandled_Except_Handler,
  82                   "__gnat_unhandled_except_handler");
  83    --  Called for handle unhandled exceptions, ie the last chance handler
  84    --  on platforms (such as SEH) that never returns after throwing an
  85    --  exception. Called directly by gigi.
  86
  87    function CleanupUnwind_Handler
  88      (UW_Version   : Integer;
  89       UW_Phases    : Unwind_Action;
  90       UW_Eclass    : Exception_Class;
  91       UW_Exception : not null GCC_Exception_Access;
  92       UW_Context   : System.Address;
  93       UW_Argument  : System.Address) return Unwind_Reason_Code;
  94    pragma Import (C, CleanupUnwind_Handler,
  95                   "__gnat_cleanupunwind_handler");
  96    --  Hook called at each step of the forced unwinding we perform to trigger
  97    --  cleanups found during the propagation of an unhandled exception.
  98
  99    --  GCC runtime functions used. These are C non-void functions, actually,
 100    --  but we ignore the return values. See raise.c as to why we are using
 101    --  __gnat stubs for these.
 102
 103    procedure Unwind_RaiseException
 104      (UW_Exception : not null GCC_Exception_Access);
 105    pragma Import (C, Unwind_RaiseException, "__gnat_Unwind_RaiseException");
 106
 107    procedure Unwind_ForcedUnwind
 108      (UW_Exception : not null GCC_Exception_Access;
 109       UW_Handler   : System.Address;
 110       UW_Argument  : System.Address);
 111    pragma Import (C, Unwind_ForcedUnwind, "__gnat_Unwind_ForcedUnwind");
 112
 113    procedure Set_Exception_Parameter
 114      (Excep         : EOA;
 115       GCC_Exception : not null GCC_Exception_Access);
 116    pragma Export
 117      (C, Set_Exception_Parameter, "__gnat_set_exception_parameter");
 118    --  Called inserted by gigi to initialize the exception parameter
 119
 120    procedure Set_Foreign_Occurrence (Excep : EOA; Mo : System.Address);
 121    --  Utility routine to initialize occurrence Excep from a foreign exception
 122    --  whose machine occurrence is Mo. The message is empty, the backtrace
 123    --  is empty too and the exception identity is Foreign_Exception.
 124
 125    --  Hooks called when entering/leaving an exception handler for a given
 126    --  occurrence, aimed at handling the stack of active occurrences. The
 127    --  calls are generated by gigi in tree_transform/N_Exception_Handler.
 128
 129    procedure Begin_Handler (GCC_Exception : not null GCC_Exception_Access);
 130    pragma Export (C, Begin_Handler, "__gnat_begin_handler");
 131
 132    procedure End_Handler (GCC_Exception : GCC_Exception_Access);
 133    pragma Export (C, End_Handler, "__gnat_end_handler");
 134
 135    --------------------------------------------------------------------
 136    -- Accessors to Basic Components of a GNAT Exception Data Pointer --
 137    --------------------------------------------------------------------
 138
 139    --  As of today, these are only used by the C implementation of the GCC
 140    --  propagation personality routine to avoid having to rely on a C
 141    --  counterpart of the whole exception_data structure, which is both
 142    --  painful and error prone. These subprograms could be moved to a more
 143    --  widely visible location if need be.
 144
 145    function Is_Handled_By_Others (E : Exception_Data_Ptr) return Boolean;
 146    pragma Export (C, Is_Handled_By_Others, "__gnat_is_handled_by_others");
 147    pragma Warnings (Off, Is_Handled_By_Others);
 148
 149    function Language_For (E : Exception_Data_Ptr) return Character;
 150    pragma Export (C, Language_For, "__gnat_language_for");
 151
 152    function Foreign_Data_For (E : Exception_Data_Ptr) return Address;
 153    pragma Export (C, Foreign_Data_For, "__gnat_foreign_data_for");
 154
 155    function EID_For (GNAT_Exception : not null GNAT_GCC_Exception_Access)
 156      return Exception_Id;
 157    pragma Export (C, EID_For, "__gnat_eid_for");
 158
 159    ---------------------------------------------------------------------------
 160    -- Objects to materialize "others" and "all others" in the GCC EH tables --
 161    ---------------------------------------------------------------------------
 162
 163    --  Currently, these only have their address taken and compared so there is
 164    --  no real point having whole exception data blocks allocated. Note that
 165    --  there are corresponding declarations in gigi (trans.c) which must be
 166    --  kept properly synchronized.
 167
 168    Others_Value : constant Character := 'O';
 169    pragma Export (C, Others_Value, "__gnat_others_value");
 170
 171    All_Others_Value : constant Character := 'A';
 172    pragma Export (C, All_Others_Value, "__gnat_all_others_value");
 173
 174    Unhandled_Others_Value : constant Character := 'U';
 175    pragma Export (C, Unhandled_Others_Value, "__gnat_unhandled_others_value");
 176    --  Special choice (emitted by gigi) to catch and notify unhandled
 177    --  exceptions on targets which always handle exceptions (such as SEH).
 178    --  The handler will simply call Unhandled_Except_Handler.
 179
 180    -------------------------
 181    -- Allocate_Occurrence --
 182    -------------------------
 183
 184    function Allocate_Occurrence return EOA is
 185       Res : GNAT_GCC_Exception_Access;
 186
 187    begin
 188       Res := New_Occurrence;
 189       Res.Header.Cleanup := GNAT_GCC_Exception_Cleanup'Address;
 190       Res.Occurrence.Machine_Occurrence := Res.all'Address;
 191
 192       return Res.Occurrence'Access;
 193    end Allocate_Occurrence;
 194
 195    --------------------------------
 196    -- GNAT_GCC_Exception_Cleanup --
 197    --------------------------------
 198
 199    procedure GNAT_GCC_Exception_Cleanup
 200      (Reason : Unwind_Reason_Code;
 201       Excep  : not null GNAT_GCC_Exception_Access)
 202    is
 203       pragma Unreferenced (Reason);
 204
 205       procedure Free is new Unchecked_Deallocation
 206         (GNAT_GCC_Exception, GNAT_GCC_Exception_Access);
 207
 208       Copy : GNAT_GCC_Exception_Access := Excep;
 209
 210    begin
 211       --  Simply free the memory
 212
 213       Free (Copy);
 214    end GNAT_GCC_Exception_Cleanup;
 215
 216    ----------------------------
 217    -- Set_Foreign_Occurrence --
 218    ----------------------------
 219
 220    procedure Set_Foreign_Occurrence (Excep : EOA; Mo : System.Address) is
 221    begin
 222       Excep.all := (
 223         Id                 => Foreign_Exception'Access,
 224         Machine_Occurrence => Mo,
 225         Msg                => <>,
 226         Msg_Length         => 0,
 227         Exception_Raised   => True,
 228         Pid                => Local_Partition_ID,
 229         Num_Tracebacks     => 0,
 230         Tracebacks         => <>);
 231    end Set_Foreign_Occurrence;
 232
 233    -------------------------
 234    -- Setup_Current_Excep --
 235    -------------------------
 236
 237    function Setup_Current_Excep
 238      (GCC_Exception : not null GCC_Exception_Access) return EOA
 239    is
 240       Excep : constant EOA := Get_Current_Excep.all;
 241
 242    begin
 243       --  Setup the exception occurrence
 244
 245       if GCC_Exception.Class = GNAT_Exception_Class then
 246
 247          --  From the GCC exception
 248
 249          declare
 250             GNAT_Occurrence : constant GNAT_GCC_Exception_Access :=
 251                                 To_GNAT_GCC_Exception (GCC_Exception);
 252          begin
 253             Excep.all := GNAT_Occurrence.Occurrence;
 254             return GNAT_Occurrence.Occurrence'Access;
 255          end;
 256
 257       else
 258          --  A default one
 259
 260          Set_Foreign_Occurrence (Excep, GCC_Exception.all'Address);
 261
 262          return Excep;
 263       end if;
 264    end Setup_Current_Excep;
 265
 266    -------------------
 267    -- Begin_Handler --
 268    -------------------
 269
 270    procedure Begin_Handler (GCC_Exception : not null GCC_Exception_Access) is
 271       pragma Unreferenced (GCC_Exception);
 272    begin
 273       null;
 274    end Begin_Handler;
 275
 276    -----------------
 277    -- End_Handler --
 278    -----------------
 279
 280    procedure End_Handler (GCC_Exception : GCC_Exception_Access) is
 281    begin
 282       if GCC_Exception /= null then
 283
 284          --  The exception might have been reraised, in this case the cleanup
 285          --  mustn't be called.
 286
 287          Unwind_DeleteException (GCC_Exception);
 288       end if;
 289    end End_Handler;
 290
 291    -----------------------------
 292    -- Reraise_GCC_Exception --
 293    -----------------------------
 294
 295    procedure Reraise_GCC_Exception
 296      (GCC_Exception : not null GCC_Exception_Access)
 297    is
 298    begin
 299       --  Simply propagate it
 300
 301       Propagate_GCC_Exception (GCC_Exception);
 302    end Reraise_GCC_Exception;
 303
 304    -----------------------------
 305    -- Propagate_GCC_Exception --
 306    -----------------------------
 307
 308    --  Call Unwind_RaiseException to actually throw, taking care of handling
 309    --  the two phase scheme it implements.
 310
 311    procedure Propagate_GCC_Exception
 312      (GCC_Exception : not null GCC_Exception_Access)
 313    is
 314       Excep : EOA;
 315
 316    begin
 317       --  Perform a standard raise first. If a regular handler is found, it
 318       --  will be entered after all the intermediate cleanups have run. If
 319       --  there is no regular handler, it will return.
 320
 321       Unwind_RaiseException (GCC_Exception);
 322
 323       --  If we get here we know the exception is not handled, as otherwise
 324       --  Unwind_RaiseException arranges for the handler to be entered. Take
 325       --  the necessary steps to enable the debugger to gain control while the
 326       --  stack is still intact.
 327
 328       Excep := Setup_Current_Excep (GCC_Exception);
 329       Notify_Unhandled_Exception (Excep);
 330
 331       --  Now, un a forced unwind to trigger cleanups. Control should not
 332       --  resume there, if there are cleanups and in any cases as the
 333       --  unwinding hook calls Unhandled_Exception_Terminate when end of
 334       --  stack is reached.
 335
 336       Unwind_ForcedUnwind
 337         (GCC_Exception,
 338          CleanupUnwind_Handler'Address,
 339          System.Null_Address);
 340
 341       --  We get here in case of error. The debugger has been notified before
 342       --  the second step above.
 343
 344       Unhandled_Except_Handler (GCC_Exception);
 345    end Propagate_GCC_Exception;
 346
 347    -------------------------
 348    -- Propagate_Exception --
 349    -------------------------
 350
 351    procedure Propagate_Exception (Excep : EOA) is
 352    begin
 353       Propagate_GCC_Exception (To_GCC_Exception (Excep.Machine_Occurrence));
 354    end Propagate_Exception;
 355
 356    -----------------------------
 357    -- Set_Exception_Parameter --
 358    -----------------------------
 359
 360    procedure Set_Exception_Parameter
 361      (Excep         : EOA;
 362       GCC_Exception : not null GCC_Exception_Access)
 363    is
 364    begin
 365       --  Setup the exception occurrence
 366
 367       if GCC_Exception.Class = GNAT_Exception_Class then
 368
 369          --  From the GCC exception
 370
 371          declare
 372             GNAT_Occurrence : constant GNAT_GCC_Exception_Access :=
 373                                 To_GNAT_GCC_Exception (GCC_Exception);
 374          begin
 375             Save_Occurrence (Excep.all, GNAT_Occurrence.Occurrence);
 376          end;
 377
 378       else
 379          --  A default one
 380
 381          Set_Foreign_Occurrence (Excep, GCC_Exception.all'Address);
 382       end if;
 383    end Set_Exception_Parameter;
 384
 385    ------------------------------
 386    -- Unhandled_Except_Handler --
 387    ------------------------------
 388
 389    procedure Unhandled_Except_Handler
 390      (GCC_Exception : not null GCC_Exception_Access)
 391    is
 392       Excep : EOA;
 393    begin
 394       Excep := Setup_Current_Excep (GCC_Exception);
 395       Unhandled_Exception_Terminate (Excep);
 396    end Unhandled_Except_Handler;
 397
 398    -------------
 399    -- EID_For --
 400    -------------
 401
 402    function EID_For
 403      (GNAT_Exception : not null GNAT_GCC_Exception_Access) return Exception_Id
 404    is
 405    begin
 406       return GNAT_Exception.Occurrence.Id;
 407    end EID_For;
 408
 409    ----------------------
 410    -- Foreign_Data_For --
 411    ----------------------
 412
 413    function Foreign_Data_For
 414      (E : SSL.Exception_Data_Ptr) return Address
 415    is
 416    begin
 417       return E.Foreign_Data;
 418    end Foreign_Data_For;
 419
 420    --------------------------
 421    -- Is_Handled_By_Others --
 422    --------------------------
 423
 424    function Is_Handled_By_Others (E : SSL.Exception_Data_Ptr) return Boolean is
 425    begin
 426       return not E.all.Not_Handled_By_Others;
 427    end Is_Handled_By_Others;
 428
 429    ------------------
 430    -- Language_For --
 431    ------------------
 432
 433    function Language_For (E : SSL.Exception_Data_Ptr) return Character is
 434    begin
 435       return E.all.Lang;
 436    end Language_For;
 437
 438 end Exception_Propagation;