gcc/ada/g-curexc.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT LIBRARY COMPONENTS                          --
   4 --                                                                          --
   5 --               G N A T . C U R R E N T _ E X C E P T I O N                --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --         Copyright (C) 1996-2004 Ada Core Technologies, 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 --  This package provides routines for obtaining the current exception
  35 --  information in Ada 83 style. In Ada 83, there was no official method
  36 --  for obtaining exception information, but a number of vendors supplied
  37 --  routines for this purpose, and this package closely approximates the
  38 --  interfaces supplied by DEC Ada 83 and VADS Ada.
  39
  40 --  The routines in this package are associated with a particular exception
  41 --  handler, and can only be called from within an exception handler. See
  42 --  also the package GNAT.Most_Recent_Exception, which provides access to
  43 --  the most recently raised exception, and is not limited to static calls
  44 --  from an exception handler.
  45
  46 package GNAT.Current_Exception is
  47 pragma Pure (Current_Exception);
  48
  49    -----------------
  50    -- Subprograms --
  51    -----------------
  52
  53    --  Note: the lower bound of returnd String values is always one.
  54
  55    function Exception_Information return String;
  56    --  Returns the result of calling Ada.Exceptions.Exception_Information
  57    --  with an argument that is the Exception_Occurrence corresponding to
  58    --  the current exception. Returns the null string if called from outside
  59    --  an exception handler.
  60
  61    function Exception_Message return String;
  62    --  Returns the result of calling Ada.Exceptions.Exception_Message with
  63    --  an argument that is the Exception_Occurrence corresponding to the
  64    --  current exception. Returns the null string if called from outside an
  65    --  exception handler.
  66
  67    function Exception_Name return String;
  68    --  Returns the result of calling Ada.Exceptions.Exception_Name with
  69    --  an argument that is the Exception_Occurrence corresponding to the
  70    --  current exception. Returns the null string if called from outside
  71    --  an exception handler.
  72
  73    --  Note: all these functions return useful information only if
  74    --  called statically from within an exception handler, and they
  75    --  return information about the exception corresponding to the
  76    --  handler in which they appear. This is NOT the same as the most
  77    --  recently raised exception. Consider the example:
  78
  79    --     exception
  80    --        when Constraint_Error =>
  81    --          begin
  82    --             ...
  83    --          exception
  84    --             when Tasking_Error => ...
  85    --          end;
  86    --
  87    --          -- Exception_xxx at this point returns the information about
  88    --          -- the constraint error, not about any exception raised within
  89    --          -- the nested block since it is the static nesting that counts.
  90
  91    -----------------------------------
  92    -- Use of Library Level Renaming --
  93    -----------------------------------
  94
  95    --  For greater compatibility with existing legacy software, library
  96    --  level renaming may be used to create a function with a name matching
  97    --  one that is in use. For example, some versions of VADS Ada provided
  98    --  a functin called Current_Exception whose semantics was identical to
  99    --  that of GNAT. The following library level renaming declaration:
 100
 101    --    with GNAT.Current_Exception;
 102    --    function Current_Exception
 103    --      renames GNAT.Current_Exception.Exception_Name;
 104
 105    --  placed in a file called current_exception.ads and compiled into the
 106    --  application compilation environment, will make the function available
 107    --  in a manner exactly compatible with that in VADS Ada 83.
 108
 109 private
 110    pragma Import (Intrinsic, Exception_Information);
 111    pragma Import (intrinsic, Exception_Message);
 112    pragma Import (Intrinsic, Exception_Name);
 113
 114 end GNAT.Current_Exception;