gcc/ada/libgnat/g-cppexc.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                  G N A T . C P P _ E X C E P T I O N S                   --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --                        Copyright (C) 2013-2019, AdaCore                  --
  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 with System;
  33 with System.Storage_Elements;
  34 with Interfaces.C; use Interfaces.C;
  35 with Ada.Unchecked_Conversion;
  36 with System.Standard_Library; use System.Standard_Library;
  37
  38 package body GNAT.CPP_Exceptions is
  39
  40    --  Note: all functions prefixed by __cxa are part of the c++ ABI for
  41    --  exception handling. As they are provided by the c++ library, there
  42    --  must be no dependencies on it in the compiled code of this unit, but
  43    --  there can be dependencies in instances. This is required to be able
  44    --  to build the shared library without the c++ library.
  45
  46    function To_Exception_Data_Ptr is new
  47      Ada.Unchecked_Conversion
  48        (Exception_Id, Exception_Data_Ptr);
  49    --  Convert an Exception_Id to its non-private type. This is used to get
  50    --  the RTTI of a C++ exception
  51
  52    function Get_Exception_Machine_Occurrence
  53      (X : Exception_Occurrence) return System.Address;
  54    pragma Import (Ada, Get_Exception_Machine_Occurrence,
  55                     "__gnat_get_exception_machine_occurrence");
  56    --  Imported function (from Ada.Exceptions) that returns the machine
  57    --  occurrence from an exception occurrence.
  58
  59    -------------------------
  60    -- Raise_Cpp_Exception --
  61    -------------------------
  62
  63    procedure Raise_Cpp_Exception (Id : Exception_Id; Value : T)
  64    is
  65       Id_Data : constant Exception_Data_Ptr := To_Exception_Data_Ptr (Id);
  66       --  Get a non-private view on the exception
  67
  68       type T_Acc is access all T;
  69       pragma Convention (C, T_Acc);
  70       --  Access type to the object compatible with C
  71
  72       Occ : T_Acc;
  73       --  The occurrence to propagate
  74
  75       function cxa_allocate_exception (Size : size_t) return T_Acc;
  76       pragma Import (C, cxa_allocate_exception, "__cxa_allocate_exception");
  77       --  The C++ function to allocate an occurrence
  78
  79       procedure cxa_throw (Obj : T_Acc; Tinfo : System.Address;
  80                                         Dest :  System.Address);
  81       pragma Import (C, cxa_throw, "__cxa_throw");
  82       pragma No_Return (cxa_throw);
  83       --  The C++ function to raise an exception
  84    begin
  85       --  Check the exception was imported from C++
  86
  87       if Id_Data.Lang /= 'C' then
  88          raise Constraint_Error;
  89       end if;
  90
  91       --  Allocate the C++ occurrence
  92
  93       Occ := cxa_allocate_exception (T'Size / System.Storage_Unit);
  94
  95       --  Set the object
  96
  97       Occ.all := Value;
  98
  99       --  Throw the exception
 100
 101       cxa_throw (Occ, Id_Data.Foreign_Data, System.Null_Address);
 102    end Raise_Cpp_Exception;
 103
 104    ----------------
 105    -- Get_Object --
 106    ----------------
 107
 108    function Get_Object (X : Exception_Occurrence) return T
 109    is
 110       use System;
 111       use System.Storage_Elements;
 112
 113       Unwind_Exception_Size : Natural;
 114       pragma Import (C, Unwind_Exception_Size, "__gnat_unwind_exception_size");
 115       --  Size in bytes of _Unwind_Exception
 116
 117       Exception_Addr : constant Address :=
 118         Get_Exception_Machine_Occurrence (X);
 119       --  Machine occurrence of X
 120
 121    begin
 122       --  Check the machine occurrence exists
 123
 124       if Exception_Addr = Null_Address then
 125          raise Constraint_Error;
 126       end if;
 127
 128       declare
 129          --  Import the object from the occurrence
 130          Result : T;
 131          pragma Import (Ada, Result);
 132          for Result'Address use
 133             Exception_Addr + Storage_Offset (Unwind_Exception_Size);
 134       begin
 135          --  And return it
 136          return Result;
 137       end;
 138    end Get_Object;
 139 end GNAT.CPP_Exceptions;