gcc/ada/a-exextr.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                      ADA.EXCEPTIONS.EXCEPTION_TRACES                     --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2004 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 2,  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.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, USA.                                                      --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 with Unchecked_Conversion;
  35
  36 pragma Warnings (Off);
  37 with Ada.Exceptions.Last_Chance_Handler;
  38 pragma Warnings (On);
  39 --  Bring last chance handler into closure
  40
  41 separate (Ada.Exceptions)
  42 package body Exception_Traces is
  43
  44    Nline : constant String := String'(1 => ASCII.LF);
  45    --  Convenient shortcut
  46
  47    type Exception_Action is access procedure (E : Exception_Occurrence);
  48    Global_Action : Exception_Action := null;
  49    pragma Export
  50      (Ada, Global_Action, "__gnat_exception_actions_global_action");
  51    --  Global action, executed whenever an exception is raised.  Changing the
  52    --  export name must be coordinated with code in g-excact.adb.
  53
  54    Raise_Hook_Initialized : Boolean := False;
  55    pragma Export
  56      (Ada, Raise_Hook_Initialized, "__gnat_exception_actions_initialized");
  57
  58    procedure Last_Chance_Handler
  59      (Except :  Exception_Occurrence);
  60    pragma Import (C, Last_Chance_Handler, "__gnat_last_chance_handler");
  61    pragma No_Return (Last_Chance_Handler);
  62    --  Users can replace the default version of this routine,
  63    --  Ada.Exceptions.Last_Chance_Handler.
  64
  65    function To_Action is new Unchecked_Conversion
  66      (Raise_Action, Exception_Action);
  67
  68    -----------------------
  69    -- Local Subprograms --
  70    -----------------------
  71
  72    procedure Notify_Exception (Excep : EOA; Is_Unhandled : Boolean);
  73    --  Factorizes the common processing for Notify_Handled_Exception and
  74    --  Notify_Unhandled_Exception. Is_Unhandled is set to True only in the
  75    --  latter case because Notify_Handled_Exception may be called for an
  76    --  actually unhandled occurrence in the Front-End-SJLJ case.
  77
  78    ---------------------------------
  79    -- Debugger Interface Routines --
  80    ---------------------------------
  81
  82    --  The routines here are null routines that normally have no effect.
  83    --  They are provided for the debugger to place breakpoints on their
  84    --  entry points to get control on an exception.
  85
  86    procedure Unhandled_Exception;
  87    pragma Export (C, Unhandled_Exception, "__gnat_unhandled_exception");
  88    --  Hook for GDB to support "break exception unhandled".
  89
  90    --  For "break exception", GDB uses __gnat_raise_nodefer_with_msg, which
  91    --  is not in this section because it fullfills other purposes than a mere
  92    --  debugger interface.
  93
  94    --------------------------------
  95    -- Import Run-Time C Routines --
  96    --------------------------------
  97
  98    --  The purpose of the following pragma Import is to ensure that we
  99    --  generate appropriate subprogram descriptors for all C routines in
 100    --  the standard GNAT library that can raise exceptions. This ensures
 101    --  that the exception propagation can properly find these routines
 102
 103    pragma Propagate_Exceptions;
 104
 105    ----------------------
 106    -- Notify_Exception --
 107    ----------------------
 108
 109    procedure Notify_Exception (Excep : EOA; Is_Unhandled : Boolean) is
 110    begin
 111       --  Output the exception information required by the Exception_Trace
 112       --  configuration. Take care not to output information about internal
 113       --  exceptions.
 114
 115       --  ??? In the Front-End ZCX case, the traceback entries we have at this
 116       --  point only include the ones we stored while walking up the stack *up
 117       --  to the handler*. All the frames above the subprogram in which the
 118       --  handler is found are missing.
 119
 120       if not Excep.Id.Not_Handled_By_Others
 121         and then
 122         (Exception_Trace = Every_Raise
 123          or else (Exception_Trace = Unhandled_Raise and then Is_Unhandled))
 124       then
 125          To_Stderr (Nline);
 126
 127          if Is_Unhandled then
 128             To_Stderr ("Unhandled ");
 129          end if;
 130
 131          To_Stderr ("Exception raised");
 132          To_Stderr (Nline);
 133          To_Stderr (Tailored_Exception_Information (Excep.all));
 134       end if;
 135
 136       --  Call the user-specific actions
 137       --  ??? We should presumably look at the reraise status here.
 138
 139       if Raise_Hook_Initialized
 140         and then Exception_Data_Ptr (Excep.Id).Raise_Hook /= null
 141       then
 142          To_Action (Exception_Data_Ptr (Excep.Id).Raise_Hook) (Excep.all);
 143       end if;
 144
 145       if Global_Action /= null then
 146          Global_Action (Excep.all);
 147       end if;
 148    end Notify_Exception;
 149
 150    ------------------------------
 151    -- Notify_Handled_Exception --
 152    ------------------------------
 153
 154    procedure Notify_Handled_Exception is
 155    begin
 156       Notify_Exception (Get_Current_Excep.all, Is_Unhandled => False);
 157    end Notify_Handled_Exception;
 158
 159    --------------------------------
 160    -- Notify_Unhandled_Exception --
 161    --------------------------------
 162
 163    procedure Notify_Unhandled_Exception is
 164    begin
 165       Notify_Exception (Get_Current_Excep.all, Is_Unhandled => True);
 166       Unhandled_Exception;
 167    end Notify_Unhandled_Exception;
 168
 169    -------------------------
 170    -- Unhandled_Exception --
 171    -------------------------
 172
 173    procedure Unhandled_Exception is
 174    begin
 175       null;
 176    end Unhandled_Exception;
 177
 178    -----------------------------------
 179    -- Unhandled_Exception_Terminate --
 180    -----------------------------------
 181
 182    procedure Unhandled_Exception_Terminate is
 183       Excep : constant EOA := Save_Occurrence (Get_Current_Excep.all.all);
 184       --  This occurrence will be used to display a message after finalization.
 185       --  It is necessary to save a copy here, or else the designated value
 186       --  could be overwritten if an exception is raised during finalization
 187       --  (even if that exception is caught).
 188
 189    begin
 190       Last_Chance_Handler (Excep.all);
 191    end Unhandled_Exception_Terminate;
 192
 193
 194    ------------------------------------
 195    -- Handling GNAT.Exception_Traces --
 196    ------------------------------------
 197
 198    --  The bulk of exception traces output is centralized in Notify_Exception,
 199    --  for both the Handled and Unhandled cases. Extra task specific output is
 200    --  triggered in the task wrapper for unhandled occurrences in tasks. It is
 201    --  not performed in this unit to avoid dragging dependencies against the
 202    --  tasking units here.
 203
 204    --  We used to rely on the output performed by Unhanded_Exception_Terminate
 205    --  for the case of an unhandled occurrence in the environment thread, and
 206    --  the task wrapper was responsible for the whole output in the tasking
 207    --  case.
 208
 209    --  This initial scheme had a drawback: the output from Terminate only
 210    --  occurs after finalization is done, which means possibly never if some
 211    --  tasks keep hanging around.
 212
 213    --  The first "presumably obvious" fix consists in moving the Terminate
 214    --  output before the finalization. It has not been retained because it
 215    --  introduces annoying changes in output orders when the finalization
 216    --  itself issues outputs, this also in "regular" cases not resorting to
 217    --  Exception_Traces.
 218
 219    --  Today's solution has the advantage of simplicity and better isolates
 220    --  the Exception_Traces machinery.
 221
 222    --  It currently outputs the information about unhandled exceptions twice
 223    --  in the environment thread, once in the notification routine and once in
 224    --  the termination routine. Avoiding the second output is possible but so
 225    --  far has been considered undesirable. It would mean changing the order
 226    --  of outputs between the two runs with or without exception traces, while
 227    --  it seems preferrable to only have additional outputs in the former
 228    --  case.
 229
 230 end Exception_Traces;