a-exexpr.adb

------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--  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 --
--                                                                          --
--                                 B o d y                                  --
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--          Copyright (C) 1992-2011, Free Software Foundation, Inc.         --
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-- GNAT is free software;  you can  redistribute it  and/or modify it under --
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-- You should have received a copy of the GNU General Public License and    --
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-- <http://www.gnu.org/licenses/>.                                          --
--                                                                          --
-- GNAT was originally developed  by the GNAT team at  New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc.      --
--                                                                          --
------------------------------------------------------------------------------

--  This is the default version, using the __builtin_setjmp/longjmp EH
--  mechanism.

with Ada.Unchecked_Conversion;

separate (Ada.Exceptions)
package body Exception_Propagation is

   --  Common binding to __builtin_longjmp for sjlj variants.

   procedure builtin_longjmp (buffer : System.Address; Flag : Integer);
   pragma No_Return (builtin_longjmp);
   pragma Import (Intrinsic, builtin_longjmp, "__builtin_longjmp");

   -------------------------
   -- Propagate_Exception --
   -------------------------

   procedure Propagate_Exception
   is
      Jumpbuf_Ptr : constant Address := Get_Jmpbuf_Address.all;
      Excep       : constant EOA := Get_Current_Excep.all;
   begin
      --  Compute the backtrace for this occurrence if corresponding binder
      --  option has been set. Call_Chain takes care of the reraise case.

      Call_Chain (Excep);

      --  Note on above call to Call_Chain:

      --  We used to only do this if From_Signal_Handler was not set,
      --  based on the assumption that backtracing from a signal handler
      --  would not work due to stack layout oddities. However, since

      --   1. The flag is never set in tasking programs (Notify_Exception
      --      performs regular raise statements), and

      --   2. No problem has shown up in tasking programs around here so
      --      far, this turned out to be too strong an assumption.

      --  As, in addition, the test was

      --   1. preventing the production of backtraces in non-tasking
      --      programs, and

      --   2. introducing a behavior inconsistency between
      --      the tasking and non-tasking cases,

      --  we have simply removed it

      --  If the jump buffer pointer is non-null, transfer control using
      --  it. Otherwise announce an unhandled exception (note that this
      --  means that we have no finalizations to do other than at the outer
      --  level). Perform the necessary notification tasks in both cases.

      if Jumpbuf_Ptr /= Null_Address then
         if not Excep.Exception_Raised then
            Excep.Exception_Raised := True;
            Exception_Traces.Notify_Handled_Exception;
         end if;

         builtin_longjmp (Jumpbuf_Ptr, 1);

      else
         Exception_Traces.Notify_Unhandled_Exception;
         Exception_Traces.Unhandled_Exception_Terminate;
      end if;
   end Propagate_Exception;

end Exception_Propagation;