748 lines
26 KiB
Ada
748 lines
26 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- S E M _ C H 1 1 --
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-- --
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-- B o d y --
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-- --
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-- Copyright (C) 1992-2016, Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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-- for more details. You should have received a copy of the GNU General --
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-- Public License distributed with GNAT; see file COPYING3. If not, go to --
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-- http://www.gnu.org/licenses for a complete copy of the license. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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with Atree; use Atree;
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with Checks; use Checks;
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with Einfo; use Einfo;
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with Errout; use Errout;
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with Lib; use Lib;
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with Lib.Xref; use Lib.Xref;
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with Namet; use Namet;
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with Nlists; use Nlists;
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with Nmake; use Nmake;
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with Opt; use Opt;
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with Restrict; use Restrict;
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with Rident; use Rident;
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with Rtsfind; use Rtsfind;
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with Sem; use Sem;
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with Sem_Aux; use Sem_Aux;
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with Sem_Ch5; use Sem_Ch5;
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with Sem_Ch8; use Sem_Ch8;
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with Sem_Ch13; use Sem_Ch13;
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with Sem_Res; use Sem_Res;
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with Sem_Util; use Sem_Util;
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with Sem_Warn; use Sem_Warn;
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with Sinfo; use Sinfo;
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with Snames; use Snames;
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with Stand; use Stand;
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package body Sem_Ch11 is
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-----------------------------------
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-- Analyze_Exception_Declaration --
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-----------------------------------
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procedure Analyze_Exception_Declaration (N : Node_Id) is
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Id : constant Entity_Id := Defining_Identifier (N);
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PF : constant Boolean := Is_Pure (Current_Scope);
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begin
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Generate_Definition (Id);
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Enter_Name (Id);
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Set_Ekind (Id, E_Exception);
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Set_Etype (Id, Standard_Exception_Type);
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Set_Is_Statically_Allocated (Id);
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Set_Is_Pure (Id, PF);
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if Has_Aspects (N) then
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Analyze_Aspect_Specifications (N, Id);
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end if;
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end Analyze_Exception_Declaration;
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--------------------------------
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-- Analyze_Exception_Handlers --
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--------------------------------
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procedure Analyze_Exception_Handlers (L : List_Id) is
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Handler : Node_Id;
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Choice : Entity_Id;
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Id : Node_Id;
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H_Scope : Entity_Id := Empty;
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procedure Check_Duplication (Id : Node_Id);
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-- Iterate through the identifiers in each handler to find duplicates
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function Others_Present return Boolean;
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-- Returns True if others handler is present
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-----------------------
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-- Check_Duplication --
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-----------------------
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procedure Check_Duplication (Id : Node_Id) is
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Handler : Node_Id;
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Id1 : Node_Id;
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Id_Entity : Entity_Id := Entity (Id);
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begin
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if Present (Renamed_Entity (Id_Entity)) then
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Id_Entity := Renamed_Entity (Id_Entity);
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end if;
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Handler := First_Non_Pragma (L);
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while Present (Handler) loop
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Id1 := First (Exception_Choices (Handler));
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while Present (Id1) loop
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-- Only check against the exception choices which precede
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-- Id in the handler, since the ones that follow Id have not
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-- been analyzed yet and will be checked in a subsequent call.
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if Id = Id1 then
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return;
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elsif Nkind (Id1) /= N_Others_Choice
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and then
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(Id_Entity = Entity (Id1)
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or else (Id_Entity = Renamed_Entity (Entity (Id1))))
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then
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if Handler /= Parent (Id) then
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Error_Msg_Sloc := Sloc (Id1);
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Error_Msg_NE ("exception choice duplicates &#", Id, Id1);
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else
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if Ada_Version = Ada_83
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and then Comes_From_Source (Id)
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then
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Error_Msg_N
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("(Ada 83): duplicate exception choice&", Id);
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end if;
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end if;
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end if;
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Next_Non_Pragma (Id1);
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end loop;
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Next (Handler);
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end loop;
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end Check_Duplication;
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--------------------
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-- Others_Present --
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--------------------
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function Others_Present return Boolean is
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H : Node_Id;
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begin
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H := First (L);
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while Present (H) loop
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if Nkind (H) /= N_Pragma
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and then Nkind (First (Exception_Choices (H))) = N_Others_Choice
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then
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return True;
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end if;
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Next (H);
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end loop;
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return False;
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end Others_Present;
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-- Start of processing for Analyze_Exception_Handlers
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begin
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Handler := First (L);
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Check_Restriction (No_Exceptions, Handler);
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Check_Restriction (No_Exception_Handlers, Handler);
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-- Kill current remembered values, since we don't know where we were
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-- when the exception was raised.
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Kill_Current_Values;
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-- Loop through handlers (which can include pragmas)
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while Present (Handler) loop
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-- If pragma just analyze it
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if Nkind (Handler) = N_Pragma then
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Analyze (Handler);
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-- Otherwise we have a real exception handler
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else
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-- Deal with choice parameter. The exception handler is a
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-- declarative part for the choice parameter, so it constitutes a
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-- scope for visibility purposes. We create an entity to denote
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-- the whole exception part, and use it as the scope of all the
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-- choices, which may even have the same name without conflict.
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-- This scope plays no other role in expansion or code generation.
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Choice := Choice_Parameter (Handler);
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if Present (Choice) then
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Set_Local_Raise_Not_OK (Handler);
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if Comes_From_Source (Choice) then
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Check_Restriction (No_Exception_Propagation, Choice);
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Set_Debug_Info_Needed (Choice);
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end if;
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if No (H_Scope) then
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H_Scope :=
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New_Internal_Entity
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(E_Block, Current_Scope, Sloc (Choice), 'E');
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Set_Is_Exception_Handler (H_Scope);
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end if;
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Push_Scope (H_Scope);
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Set_Etype (H_Scope, Standard_Void_Type);
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Enter_Name (Choice);
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Set_Ekind (Choice, E_Variable);
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if RTE_Available (RE_Exception_Occurrence) then
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Set_Etype (Choice, RTE (RE_Exception_Occurrence));
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end if;
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Generate_Definition (Choice);
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-- Indicate that choice has an initial value, since in effect
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-- this field is assigned an initial value by the exception.
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-- We also consider that it is modified in the source.
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Set_Has_Initial_Value (Choice, True);
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Set_Never_Set_In_Source (Choice, False);
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end if;
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Id := First (Exception_Choices (Handler));
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while Present (Id) loop
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if Nkind (Id) = N_Others_Choice then
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if Present (Next (Id))
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or else Present (Next (Handler))
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or else Present (Prev (Id))
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then
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Error_Msg_N ("OTHERS must appear alone and last", Id);
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end if;
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else
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Analyze (Id);
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-- In most cases the choice has already been analyzed in
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-- Analyze_Handled_Statement_Sequence, in order to expand
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-- local handlers. This advance analysis does not take into
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-- account the case in which a choice has the same name as
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-- the choice parameter of the handler, which may hide an
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-- outer exception. This pathological case appears in ACATS
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-- B80001_3.adb, and requires an explicit check to verify
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-- that the id is not hidden.
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if not Is_Entity_Name (Id)
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or else Ekind (Entity (Id)) /= E_Exception
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or else
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(Nkind (Id) = N_Identifier
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and then Chars (Id) = Chars (Choice))
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then
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Error_Msg_N ("exception name expected", Id);
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else
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-- Emit a warning at the declaration level when a local
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-- exception is never raised explicitly.
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if Warn_On_Redundant_Constructs
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and then not Is_Raised (Entity (Id))
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and then Scope (Entity (Id)) = Current_Scope
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then
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Error_Msg_NE
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("exception & is never raised?r?", Entity (Id), Id);
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end if;
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if Present (Renamed_Entity (Entity (Id))) then
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if Entity (Id) = Standard_Numeric_Error then
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Check_Restriction (No_Obsolescent_Features, Id);
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if Warn_On_Obsolescent_Feature then
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Error_Msg_N
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("Numeric_Error is an " &
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"obsolescent feature (RM J.6(1))?j?", Id);
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Error_Msg_N
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("\use Constraint_Error instead?j?", Id);
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end if;
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end if;
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end if;
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Check_Duplication (Id);
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-- Check for exception declared within generic formal
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-- package (which is illegal, see RM 11.2(8))
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declare
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Ent : Entity_Id := Entity (Id);
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Scop : Entity_Id;
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begin
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if Present (Renamed_Entity (Ent)) then
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Ent := Renamed_Entity (Ent);
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end if;
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Scop := Scope (Ent);
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while Scop /= Standard_Standard
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and then Ekind (Scop) = E_Package
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loop
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if Nkind (Declaration_Node (Scop)) =
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N_Package_Specification
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and then
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Nkind (Original_Node (Parent
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(Declaration_Node (Scop)))) =
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N_Formal_Package_Declaration
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then
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Error_Msg_NE
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("exception& is declared in generic formal "
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& "package", Id, Ent);
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Error_Msg_N
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("\and therefore cannot appear in handler "
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& "(RM 11.2(8))", Id);
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exit;
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-- If the exception is declared in an inner
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-- instance, nothing else to check.
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elsif Is_Generic_Instance (Scop) then
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exit;
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end if;
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Scop := Scope (Scop);
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end loop;
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end;
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end if;
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end if;
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Next (Id);
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end loop;
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-- Check for redundant handler (has only raise statement) and is
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-- either an others handler, or is a specific handler when no
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-- others handler is present.
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if Warn_On_Redundant_Constructs
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and then List_Length (Statements (Handler)) = 1
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and then Nkind (First (Statements (Handler))) = N_Raise_Statement
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and then No (Name (First (Statements (Handler))))
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and then (not Others_Present
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or else Nkind (First (Exception_Choices (Handler))) =
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N_Others_Choice)
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then
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Error_Msg_N
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("useless handler contains only a reraise statement?r?",
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Handler);
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end if;
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-- Now analyze the statements of this handler
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Analyze_Statements (Statements (Handler));
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-- If a choice was present, we created a special scope for it, so
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-- this is where we pop that special scope to get rid of it.
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if Present (Choice) then
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End_Scope;
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end if;
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end if;
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Next (Handler);
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end loop;
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end Analyze_Exception_Handlers;
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--------------------------------
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-- Analyze_Handled_Statements --
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--------------------------------
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procedure Analyze_Handled_Statements (N : Node_Id) is
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Handlers : constant List_Id := Exception_Handlers (N);
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Handler : Node_Id;
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Choice : Node_Id;
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begin
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if Present (Handlers) then
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Kill_All_Checks;
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end if;
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-- We are now going to analyze the statements and then the exception
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-- handlers. We certainly need to do things in this order to get the
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-- proper sequential semantics for various warnings.
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-- However, there is a glitch. When we process raise statements, an
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-- optimization is to look for local handlers and specialize the code
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-- in this case.
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-- In order to detect if a handler is matching, we must have at least
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-- analyzed the choices in the proper scope so that proper visibility
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-- analysis is performed. Hence we analyze just the choices first,
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-- before we analyze the statement sequence.
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Handler := First_Non_Pragma (Handlers);
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while Present (Handler) loop
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Choice := First_Non_Pragma (Exception_Choices (Handler));
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while Present (Choice) loop
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Analyze (Choice);
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Next_Non_Pragma (Choice);
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end loop;
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Next_Non_Pragma (Handler);
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end loop;
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-- Analyze statements in sequence
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Analyze_Statements (Statements (N));
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-- If the current scope is a subprogram, entry or task body or declare
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-- block then this is the right place to check for hanging useless
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-- assignments from the statement sequence. Skip this in the body of a
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-- postcondition, since in that case there are no source references, and
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-- we need to preserve deferred references from the enclosing scope.
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if ((Is_Subprogram (Current_Scope) or else Is_Entry (Current_Scope))
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and then Chars (Current_Scope) /= Name_uPostconditions)
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or else Ekind_In (Current_Scope, E_Block, E_Task_Type)
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then
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Warn_On_Useless_Assignments (Current_Scope);
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end if;
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-- Deal with handlers or AT END proc
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if Present (Handlers) then
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Analyze_Exception_Handlers (Handlers);
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elsif Present (At_End_Proc (N)) then
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Analyze (At_End_Proc (N));
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end if;
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end Analyze_Handled_Statements;
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------------------------------
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-- Analyze_Raise_Expression --
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------------------------------
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procedure Analyze_Raise_Expression (N : Node_Id) is
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Exception_Id : constant Node_Id := Name (N);
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Exception_Name : Entity_Id := Empty;
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begin
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if Comes_From_Source (N) then
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Check_Compiler_Unit ("raise expression", N);
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end if;
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Check_SPARK_05_Restriction ("raise expression is not allowed", N);
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-- Check exception restrictions on the original source
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if Comes_From_Source (N) then
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Check_Restriction (No_Exceptions, N);
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end if;
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Analyze (Exception_Id);
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if Is_Entity_Name (Exception_Id) then
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Exception_Name := Entity (Exception_Id);
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end if;
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if No (Exception_Name)
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or else Ekind (Exception_Name) /= E_Exception
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then
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Error_Msg_N
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("exception name expected in raise statement", Exception_Id);
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else
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Set_Is_Raised (Exception_Name);
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end if;
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-- Deal with RAISE WITH case
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if Present (Expression (N)) then
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Analyze_And_Resolve (Expression (N), Standard_String);
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end if;
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-- Check obsolescent use of Numeric_Error
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if Exception_Name = Standard_Numeric_Error then
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Check_Restriction (No_Obsolescent_Features, Exception_Id);
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end if;
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-- Kill last assignment indication
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Kill_Current_Values (Last_Assignment_Only => True);
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|
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-- Raise_Type is compatible with all other types so that the raise
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-- expression is legal in any expression context. It will be eventually
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-- replaced by the concrete type imposed by the context.
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Set_Etype (N, Raise_Type);
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end Analyze_Raise_Expression;
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|
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-----------------------------
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-- Analyze_Raise_Statement --
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-----------------------------
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|
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procedure Analyze_Raise_Statement (N : Node_Id) is
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Exception_Id : constant Node_Id := Name (N);
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Exception_Name : Entity_Id := Empty;
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P : Node_Id;
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Par : Node_Id;
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begin
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if Comes_From_Source (N) then
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Check_SPARK_05_Restriction ("raise statement is not allowed", N);
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end if;
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Check_Unreachable_Code (N);
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|
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-- Check exception restrictions on the original source
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if Comes_From_Source (N) then
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Check_Restriction (No_Exceptions, N);
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end if;
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|
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-- Check for useless assignment to OUT or IN OUT scalar preceding the
|
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-- raise. Right now only look at assignment statements, could do more???
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if Is_List_Member (N) then
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declare
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P : Node_Id;
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L : Node_Id;
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begin
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P := Prev (N);
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-- Skip past null statements and pragmas
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while Present (P)
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and then Nkind_In (P, N_Null_Statement, N_Pragma)
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loop
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P := Prev (P);
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end loop;
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|
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-- See if preceding statement is an assignment
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if Present (P) and then Nkind (P) = N_Assignment_Statement then
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L := Name (P);
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-- Give warning for assignment to scalar formal
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if Is_Scalar_Type (Etype (L))
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and then Is_Entity_Name (L)
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and then Is_Formal (Entity (L))
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|
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-- Do this only for parameters to the current subprogram.
|
|
-- This avoids some false positives for the nested case.
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|
|
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and then Nearest_Dynamic_Scope (Current_Scope) =
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Scope (Entity (L))
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then
|
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-- Don't give warning if we are covered by an exception
|
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-- handler, since this may result in false positives, since
|
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-- the handler may handle the exception and return normally.
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|
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-- First find the enclosing handled sequence of statements
|
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-- (note, we could also look for a handler in an outer block
|
|
-- but currently we don't, and in that case we'll emit the
|
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-- warning).
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Par := N;
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loop
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Par := Parent (Par);
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exit when Nkind (Par) = N_Handled_Sequence_Of_Statements;
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end loop;
|
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|
|
-- See if there is a handler, give message if not
|
|
|
|
if No (Exception_Handlers (Par)) then
|
|
Error_Msg_N
|
|
("assignment to pass-by-copy formal "
|
|
& "may have no effect??", P);
|
|
Error_Msg_N
|
|
("\RAISE statement may result in abnormal return "
|
|
& "(RM 6.4.1(17))??", P);
|
|
end if;
|
|
end if;
|
|
end if;
|
|
end;
|
|
end if;
|
|
|
|
-- Reraise statement
|
|
|
|
if No (Exception_Id) then
|
|
P := Parent (N);
|
|
while not Nkind_In (P, N_Exception_Handler,
|
|
N_Subprogram_Body,
|
|
N_Package_Body,
|
|
N_Task_Body,
|
|
N_Entry_Body)
|
|
loop
|
|
P := Parent (P);
|
|
end loop;
|
|
|
|
if Nkind (P) /= N_Exception_Handler then
|
|
Error_Msg_N
|
|
("reraise statement must appear directly in a handler", N);
|
|
|
|
-- If a handler has a reraise, it cannot be the target of a local
|
|
-- raise (goto optimization is impossible), and if the no exception
|
|
-- propagation restriction is set, this is a violation.
|
|
|
|
else
|
|
Set_Local_Raise_Not_OK (P);
|
|
|
|
-- Do not check the restriction if the reraise statement is part
|
|
-- of the code generated for an AT-END handler. That's because
|
|
-- if the restriction is actually active, we never generate this
|
|
-- raise anyway, so the apparent violation is bogus.
|
|
|
|
if not From_At_End (N) then
|
|
Check_Restriction (No_Exception_Propagation, N);
|
|
end if;
|
|
end if;
|
|
|
|
-- Normal case with exception id present
|
|
|
|
else
|
|
Analyze (Exception_Id);
|
|
|
|
if Is_Entity_Name (Exception_Id) then
|
|
Exception_Name := Entity (Exception_Id);
|
|
end if;
|
|
|
|
if No (Exception_Name)
|
|
or else Ekind (Exception_Name) /= E_Exception
|
|
then
|
|
Error_Msg_N
|
|
("exception name expected in raise statement", Exception_Id);
|
|
else
|
|
Set_Is_Raised (Exception_Name);
|
|
end if;
|
|
|
|
-- Deal with RAISE WITH case
|
|
|
|
if Present (Expression (N)) then
|
|
Analyze_And_Resolve (Expression (N), Standard_String);
|
|
end if;
|
|
end if;
|
|
|
|
-- Check obsolescent use of Numeric_Error
|
|
|
|
if Exception_Name = Standard_Numeric_Error then
|
|
Check_Restriction (No_Obsolescent_Features, Exception_Id);
|
|
end if;
|
|
|
|
-- Kill last assignment indication
|
|
|
|
Kill_Current_Values (Last_Assignment_Only => True);
|
|
end Analyze_Raise_Statement;
|
|
|
|
-----------------------------
|
|
-- Analyze_Raise_xxx_Error --
|
|
-----------------------------
|
|
|
|
-- Normally, the Etype is already set (when this node is used within
|
|
-- an expression, since it is copied from the node which it rewrites).
|
|
-- If this node is used in a statement context, then we set the type
|
|
-- Standard_Void_Type. This is used both by Gigi and by the front end
|
|
-- to distinguish the statement use and the subexpression use.
|
|
|
|
-- The only other required processing is to take care of the Condition
|
|
-- field if one is present.
|
|
|
|
procedure Analyze_Raise_xxx_Error (N : Node_Id) is
|
|
|
|
function Same_Expression (C1, C2 : Node_Id) return Boolean;
|
|
-- It often occurs that two identical raise statements are generated in
|
|
-- succession (for example when dynamic elaboration checks take place on
|
|
-- separate expressions in a call). If the two statements are identical
|
|
-- according to the simple criterion that follows, the raise is
|
|
-- converted into a null statement.
|
|
|
|
---------------------
|
|
-- Same_Expression --
|
|
---------------------
|
|
|
|
function Same_Expression (C1, C2 : Node_Id) return Boolean is
|
|
begin
|
|
if No (C1) and then No (C2) then
|
|
return True;
|
|
|
|
elsif Is_Entity_Name (C1) and then Is_Entity_Name (C2) then
|
|
return Entity (C1) = Entity (C2);
|
|
|
|
elsif Nkind (C1) /= Nkind (C2) then
|
|
return False;
|
|
|
|
elsif Nkind (C1) in N_Unary_Op then
|
|
return Same_Expression (Right_Opnd (C1), Right_Opnd (C2));
|
|
|
|
elsif Nkind (C1) in N_Binary_Op then
|
|
return Same_Expression (Left_Opnd (C1), Left_Opnd (C2))
|
|
and then
|
|
Same_Expression (Right_Opnd (C1), Right_Opnd (C2));
|
|
|
|
elsif Nkind (C1) = N_Null then
|
|
return True;
|
|
|
|
else
|
|
return False;
|
|
end if;
|
|
end Same_Expression;
|
|
|
|
-- Start of processing for Analyze_Raise_xxx_Error
|
|
|
|
begin
|
|
if Nkind (Original_Node (N)) = N_Raise_Statement then
|
|
Check_SPARK_05_Restriction ("raise statement is not allowed", N);
|
|
end if;
|
|
|
|
if No (Etype (N)) then
|
|
Set_Etype (N, Standard_Void_Type);
|
|
end if;
|
|
|
|
if Present (Condition (N)) then
|
|
Analyze_And_Resolve (Condition (N), Standard_Boolean);
|
|
end if;
|
|
|
|
-- Deal with static cases in obvious manner
|
|
|
|
if Nkind (Condition (N)) = N_Identifier then
|
|
if Entity (Condition (N)) = Standard_True then
|
|
Set_Condition (N, Empty);
|
|
|
|
elsif Entity (Condition (N)) = Standard_False then
|
|
Rewrite (N, Make_Null_Statement (Sloc (N)));
|
|
end if;
|
|
end if;
|
|
|
|
-- Remove duplicate raise statements. Note that the previous one may
|
|
-- already have been removed as well.
|
|
|
|
if not Comes_From_Source (N)
|
|
and then Nkind (N) /= N_Null_Statement
|
|
and then Is_List_Member (N)
|
|
and then Present (Prev (N))
|
|
and then Nkind (N) = Nkind (Original_Node (Prev (N)))
|
|
and then Same_Expression
|
|
(Condition (N), Condition (Original_Node (Prev (N))))
|
|
then
|
|
Rewrite (N, Make_Null_Statement (Sloc (N)));
|
|
end if;
|
|
end Analyze_Raise_xxx_Error;
|
|
|
|
end Sem_Ch11;
|