------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- S Y S T E M . E X C E P T I O N _ T A B L E --
-- --
-- B o d y --
-- --
-- Copyright (C) 1996-2023, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <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. --
-- --
------------------------------------------------------------------------------
with System.Soft_Links; use System.Soft_Links;
package body System.Exception_Table is
use System.Standard_Library;
type Hash_Val is mod 2 ** 8;
subtype Hash_Idx is Hash_Val range 1 .. 37;
HTable : array (Hash_Idx) of aliased Exception_Data_Ptr;
-- Actual hash table containing all registered exceptions
--
-- The table is very small and the hash function weak, as looking up
-- registered exceptions is rare and minimizing space and time overhead
-- of registration is more important. In addition, it is expected that the
-- exceptions that need to be looked up are registered dynamically, and
-- therefore will be at the begin of the hash chains.
--
-- The table differs from System.HTable.Static_HTable in that the final
-- element of each chain is not marked by null, but by a pointer to self.
-- This way it is possible to defend against the same entry being inserted
-- twice, without having to do a lookup which is relatively expensive for
-- programs with large number
--
-- All non-local subprograms use the global Task_Lock to protect against
-- concurrent use of the exception table. This is needed as local
-- exceptions may be declared concurrently with those declared at the
-- library level.
-- Local Subprograms
generic
with procedure Process (T : Exception_Data_Ptr; More : out Boolean);
procedure Iterate;
-- Iterate over all
function Lookup (Name : String) return Exception_Data_Ptr;
-- Find and return the Exception_Data of the exception with the given Name
-- (which must be in all uppercase), or null if none was registered.
procedure Register (Item : Exception_Data_Ptr);
-- Register an exception with the given Exception_Data in the table.
function Has_Name (Item : Exception_Data_Ptr; Name : String) return Boolean;
-- Return True iff Item.Full_Name and Name are equal. Both names are
-- assumed to be in all uppercase and end with ASCII.NUL.
function Hash (S : String) return Hash_Idx;
-- Return the index in the hash table for S, which is assumed to be all
-- uppercase and end with ASCII.NUL.
--------------
-- Has_Name --
--------------
function Has_Name (Item : Exception_Data_Ptr; Name : String) return Boolean
is
S : constant Big_String_Ptr := To_Ptr (Item.Full_Name);
J : Integer := S'First;
begin
for K in Name'Range loop
-- Note that as both items are terminated with ASCII.NUL, the
-- comparison below must fail for strings of different lengths.
if S (J) /= Name (K) then
return False;
end if;
J := J + 1;
end loop;
return True;
end Has_Name;
------------
-- Lookup --
------------
function Lookup (Name : String) return Exception_Data_Ptr is
Prev : Exception_Data_Ptr;
Curr : Exception_Data_Ptr;
begin
Curr := HTable (Hash (Name));
Prev := null;
while Curr /= Prev loop
if Has_Name (Curr, Name) then
return Curr;
end if;
Prev := Curr;
Curr := Curr.HTable_Ptr;
end loop;
return null;
end Lookup;
----------
-- Hash --
----------
function Hash (S : String) return Hash_Idx is
Hash : Hash_Val := 0;
begin
for J in S'Range loop
exit when S (J) = ASCII.NUL;
Hash := Hash xor Character'Pos (S (J));
end loop;
return Hash_Idx'First + Hash mod (Hash_Idx'Last - Hash_Idx'First + 1);
end Hash;
-------------
-- Iterate --
-------------
procedure Iterate is
More : Boolean;
Prev, Curr : Exception_Data_Ptr;
begin
Outer : for Idx in HTable'Range loop
Prev := null;
Curr := HTable (Idx);
while Curr /= Prev loop
Process (Curr, More);
exit Outer when not More;
Prev := Curr;
Curr := Curr.HTable_Ptr;
end loop;
end loop Outer;
end Iterate;
--------------
-- Register --
--------------
procedure Register (Item : Exception_Data_Ptr) is
begin
if Item.HTable_Ptr = null then
Prepend_To_Chain : declare
Chain : Exception_Data_Ptr
renames HTable (Hash (To_Ptr (Item.Full_Name).all));
begin
if Chain = null then
Item.HTable_Ptr := Item;
else
Item.HTable_Ptr := Chain;
end if;
Chain := Item;
end Prepend_To_Chain;
end if;
end Register;
-------------------------------
-- Get_Registered_Exceptions --
-------------------------------
procedure Get_Registered_Exceptions
(List : out Exception_Data_Array;
Last : out Integer)
is
procedure Get_One (Item : Exception_Data_Ptr; More : out Boolean);
-- Add Item to List (List'First .. Last) by first incrementing Last
-- and storing Item in List (Last). Last should be in List'First - 1
-- and List'Last.
procedure Get_All is new Iterate (Get_One);
-- Store all registered exceptions in List, updating Last
-------------
-- Get_One --
-------------
procedure Get_One (Item : Exception_Data_Ptr; More : out Boolean) is
begin
if Last < List'Last then
Last := Last + 1;
List (Last) := Item;
More := True;
else
More := False;
end if;
end Get_One;
begin
-- In this routine the invariant is that List (List'First .. Last)
-- contains the registered exceptions retrieved so far.
Last := List'First - 1;
Lock_Task.all;
Get_All;
Unlock_Task.all;
end Get_Registered_Exceptions;
------------------------
-- Internal_Exception --
------------------------
function Internal_Exception
(X : String;
Create_If_Not_Exist : Boolean := True) return Exception_Data_Ptr
is
-- If X was not yet registered and Create_if_Not_Exist is True,
-- dynamically allocate and register a new exception.
type String_Ptr is access all String;
Dyn_Copy : String_Ptr;
Copy : aliased String (X'First .. X'Last + 1);
Result : Exception_Data_Ptr;
begin
Lock_Task.all;
Copy (X'Range) := X;
Copy (Copy'Last) := ASCII.NUL;
Result := Lookup (Copy);
-- If unknown exception, create it on the heap. This is a legitimate
-- situation in the distributed case when an exception is defined
-- only in a partition
if Result = null and then Create_If_Not_Exist then
Dyn_Copy := new String'(Copy);
Result :=
new Exception_Data'
(Not_Handled_By_Others => False,
Lang => 'A',
Name_Length => Copy'Length,
Full_Name => Dyn_Copy.all'Address,
HTable_Ptr => null,
Foreign_Data => Null_Address,
Raise_Hook => null);
Register (Result);
end if;
Unlock_Task.all;
return Result;
end Internal_Exception;
------------------------
-- Register_Exception --
------------------------
procedure Register_Exception (X : Exception_Data_Ptr) is
begin
Lock_Task.all;
Register (X);
Unlock_Task.all;
end Register_Exception;
---------------------------------
-- Registered_Exceptions_Count --
---------------------------------
function Registered_Exceptions_Count return Natural is
Count : Natural := 0;
procedure Count_Item (Item : Exception_Data_Ptr; More : out Boolean);
-- Update Count for given Item
procedure Count_Item (Item : Exception_Data_Ptr; More : out Boolean) is
pragma Unreferenced (Item);
begin
Count := Count + 1;
More := Count < Natural'Last;
end Count_Item;
procedure Count_All is new Iterate (Count_Item);
begin
Lock_Task.all;
Count_All;
Unlock_Task.all;
return Count;
end Registered_Exceptions_Count;
begin
-- Register the standard exceptions at elaboration time
-- We don't need to use the locking version here as the elaboration
-- will not be concurrent and no tasks can call any subprograms of this
-- unit before it has been elaborated.
Register (Abort_Signal_Def'Access);
Register (Tasking_Error_Def'Access);
Register (Storage_Error_Def'Access);
Register (Program_Error_Def'Access);
Register (Numeric_Error_Def'Access);
Register (Constraint_Error_Def'Access);
end System.Exception_Table;