This patch adds code to handle the finalization of a controlled transient
variable used as an actual of a subprogram call when the call raises an
exception.
------------
-- Source --
------------
-- main.adb:
with Ada.Finalization; use Ada.Finalization;
with Ada.Text_IO; use Ada.Text_IO;
procedure Main is
type Ctrl is new Controlled with record
Id : Natural := 0;
end record;
procedure Adjust (Obj : in out Ctrl);
procedure Finalize (Obj : in out Ctrl);
procedure Adjust (Obj : in out Ctrl) is
New_Id : constant Natural := Obj.Id + 1;
begin
Put_Line (" adjust Id:" & Obj.Id'Img & " ->" & New_Id'Img);
Obj.Id := New_Id;
end Adjust;
procedure Finalize (Obj : in out Ctrl) is
begin
Put_Line (" finalize Id:" & Obj.Id'Img);
end Finalize;
function Make_Ctrl (Id : Natural) return Ctrl is
begin
return (Controlled with Id => Id);
end Make_Ctrl;
type Ctrl_Array is array (1 .. 1) of Ctrl;
procedure Raise_PE (Do_It : Boolean; Objs : Ctrl_Array) is
pragma Unreferenced (Objs);
begin
if Do_It then
raise Program_Error;
end if;
end Raise_PE;
Obj : constant Ctrl := Make_Ctrl (1);
begin
Put_Line ("before exception");
Raise_PE (True, (1 => Obj));
Put_Line ("after exception");
exception
when Program_Error => Put_Line ("exception caught");
end Main;
-------------------------------------
-- Compilation and expected output --
-------------------------------------
$ gnatmake -q -gnat05 main.adb
$ ./main
adjust Id: 1 -> 2
finalize Id: 1
adjust Id: 2 -> 3
finalize Id: 2
before exception
adjust Id: 3 -> 4
finalize Id: 4
exception caught
finalize Id: 3
Tested on x86_64-pc-linux-gnu, committed on trunk
2011-09-01 Hristian Kirtchev <kirtc...@adacore.com>
* exp_ch7.adb (Find_Insertion_List): New routine.
(Process_Transient_Objects): Add code to handle the abnormal
finalization of a controlled transient associated with a subprogram
call. Since transients are cleaned up right after the associated
context, an exception raised during a subprogram call may bypass the
finalization code.
Index: exp_ch7.adb
===================================================================
--- exp_ch7.adb (revision 178381)
+++ exp_ch7.adb (working copy)
@@ -4198,18 +4198,52 @@
Last_Object : Node_Id;
Related_Node : Node_Id)
is
- Finalizer_Data : Finalization_Exception_Data;
- Finalizer_Decls : List_Id;
- Built : Boolean := False;
- Desig : Entity_Id;
- Fin_Block : Node_Id;
- Last_Fin : Node_Id := Empty;
- Loc : Source_Ptr;
- Obj_Id : Entity_Id;
- Obj_Ref : Node_Id;
- Obj_Typ : Entity_Id;
- Stmt : Node_Id;
+ function Find_Insertion_List return List_Id;
+ -- Return the statement list of the enclosing sequence of statements
+ -------------------------
+ -- Find_Insertion_List --
+ -------------------------
+
+ function Find_Insertion_List return List_Id is
+ Par : Node_Id;
+
+ begin
+ -- Climb up the tree looking for the enclosing sequence of
+ -- statements.
+
+ Par := N;
+ while Present (Par)
+ and then Nkind (Par) /= N_Handled_Sequence_Of_Statements
+ loop
+ Par := Parent (Par);
+ end loop;
+
+ return Statements (Par);
+ end Find_Insertion_List;
+
+ -- Local variables
+
+ Requires_Hooking : constant Boolean :=
+ Nkind_In (N, N_Function_Call,
+ N_Procedure_Call_Statement);
+
+ Built : Boolean := False;
+ Desig_Typ : Entity_Id;
+ Fin_Block : Node_Id;
+ Fin_Data : Finalization_Exception_Data;
+ Fin_Decls : List_Id;
+ Last_Fin : Node_Id := Empty;
+ Loc : Source_Ptr;
+ Obj_Id : Entity_Id;
+ Obj_Ref : Node_Id;
+ Obj_Typ : Entity_Id;
+ Stmt : Node_Id;
+ Stmts : List_Id;
+ Temp_Id : Entity_Id;
+
+ -- Start of processing for Process_Transient_Objects
+
begin
-- Examine all objects in the list First_Object .. Last_Object
@@ -4224,34 +4258,151 @@
and then Stmt /= Related_Node
then
- Loc := Sloc (Stmt);
- Obj_Id := Defining_Identifier (Stmt);
- Obj_Typ := Base_Type (Etype (Obj_Id));
- Desig := Obj_Typ;
+ Loc := Sloc (Stmt);
+ Obj_Id := Defining_Identifier (Stmt);
+ Obj_Typ := Base_Type (Etype (Obj_Id));
+ Desig_Typ := Obj_Typ;
Set_Is_Processed_Transient (Obj_Id);
-- Handle access types
- if Is_Access_Type (Desig) then
- Desig := Available_View (Designated_Type (Desig));
+ if Is_Access_Type (Desig_Typ) then
+ Desig_Typ := Available_View (Designated_Type (Desig_Typ));
end if;
-- Create the necessary entities and declarations the first
-- time around.
if not Built then
- Finalizer_Decls := New_List;
- Build_Object_Declarations
- (Finalizer_Data, Finalizer_Decls, Loc);
+ Fin_Decls := New_List;
- Insert_List_Before_And_Analyze
- (First_Object, Finalizer_Decls);
+ Build_Object_Declarations (Fin_Data, Fin_Decls, Loc);
+ Insert_List_Before_And_Analyze (First_Object, Fin_Decls);
Built := True;
end if;
+ -- Transient variables associated with subprogram calls need
+ -- extra processing. These variables are usually created right
+ -- before the call and finalized immediately after the call.
+ -- If an exception occurs during the call, the clean up code
+ -- is skipped due to the sudden change in control and the
+ -- transient is never finalized.
+
+ -- To handle this case, such variables are "exported" to the
+ -- enclosing sequence of statements where their corresponding
+ -- "hooks" are picked up by the finalization machinery.
+
+ if Requires_Hooking then
+ declare
+ Ins_List : constant List_Id := Find_Insertion_List;
+ Expr : Node_Id;
+ Ptr_Decl : Node_Id;
+ Ptr_Id : Entity_Id;
+ Temp_Decl : Node_Id;
+
+ begin
+ -- Step 1: Create an access type which provides a
+ -- reference to the transient object. Generate:
+
+ -- Ann : access [all] <Desig_Typ>;
+
+ Ptr_Id := Make_Temporary (Loc, 'A');
+
+ Ptr_Decl :=
+ Make_Full_Type_Declaration (Loc,
+ Defining_Identifier => Ptr_Id,
+ Type_Definition =>
+ Make_Access_To_Object_Definition (Loc,
+ All_Present =>
+ Ekind (Obj_Typ) = E_General_Access_Type,
+ Subtype_Indication =>
+ New_Reference_To (Desig_Typ, Loc)));
+
+ -- Step 2: Create a temporary which acts as a hook to
+ -- the transient object. Generate:
+
+ -- Temp : Ptr_Id := null;
+
+ Temp_Id := Make_Temporary (Loc, 'T');
+
+ Temp_Decl :=
+ Make_Object_Declaration (Loc,
+ Defining_Identifier => Temp_Id,
+ Object_Definition =>
+ New_Reference_To (Ptr_Id, Loc));
+
+ -- Analyze the access type and the hook declarations
+
+ Prepend_To (Ins_List, Temp_Decl);
+ Prepend_To (Ins_List, Ptr_Decl);
+
+ Analyze (Ptr_Decl);
+ Analyze (Temp_Decl);
+
+ -- Mark the temporary as a transient hook. This signals
+ -- the machinery in Build_Finalizer to recognize this
+ -- special case.
+
+ Set_Return_Flag_Or_Transient_Decl (Temp_Id, Stmt);
+
+ -- Step 3: Hook the transient object to the temporary
+
+ if Is_Access_Type (Obj_Typ) then
+ Expr :=
+ Convert_To (Ptr_Id, New_Reference_To (Obj_Id, Loc));
+ else
+ Expr :=
+ Make_Attribute_Reference (Loc,
+ Prefix => New_Reference_To (Obj_Id, Loc),
+ Attribute_Name => Name_Unrestricted_Access);
+ end if;
+
+ -- Generate:
+ -- Temp := Ptr_Id (Obj_Id);
+ -- <or>
+ -- Temp := Obj_Id'Unrestricted_Access;
+
+ Insert_After_And_Analyze (Stmt,
+ Make_Assignment_Statement (Loc,
+ Name => New_Reference_To (Temp_Id, Loc),
+ Expression => Expr));
+ end;
+ end if;
+
+ Stmts := New_List;
+
+ -- The transient object is about to be finalized by the clean
+ -- up code following the subprogram call. In order to avoid
+ -- double finalization, clear the hook.
+
-- Generate:
+ -- Temp := null;
+
+ if Requires_Hooking then
+ Append_To (Stmts,
+ Make_Assignment_Statement (Loc,
+ Name => New_Reference_To (Temp_Id, Loc),
+ Expression => Make_Null (Loc)));
+ end if;
+
+ -- Generate:
+ -- [Deep_]Finalize (Obj_Ref);
+
+ Obj_Ref := New_Reference_To (Obj_Id, Loc);
+
+ if Is_Access_Type (Obj_Typ) then
+ Obj_Ref := Make_Explicit_Dereference (Loc, Obj_Ref);
+ end if;
+
+ Append_To (Stmts,
+ Make_Final_Call
+ (Obj_Ref => Obj_Ref,
+ Typ => Desig_Typ));
+
+ -- Generate:
+ -- [Temp := null;]
-- begin
-- [Deep_]Finalize (Obj_Ref);
@@ -4264,23 +4415,14 @@
-- end if;
-- end;
- Obj_Ref := New_Reference_To (Obj_Id, Loc);
-
- if Is_Access_Type (Obj_Typ) then
- Obj_Ref := Make_Explicit_Dereference (Loc, Obj_Ref);
- end if;
-
Fin_Block :=
Make_Block_Statement (Loc,
Handled_Statement_Sequence =>
Make_Handled_Sequence_Of_Statements (Loc,
- Statements => New_List (
- Make_Final_Call
- (Obj_Ref => Obj_Ref,
- Typ => Desig)),
+ Statements => Stmts,
+ Exception_Handlers => New_List (
+ Build_Exception_Handler (Fin_Data))));
- Exception_Handlers => New_List (
- Build_Exception_Handler (Finalizer_Data))));
Insert_After_And_Analyze (Last_Object, Fin_Block);
-- The raise statement must be inserted after all the
@@ -4345,7 +4487,7 @@
and then Present (Last_Fin)
then
Insert_After_And_Analyze (Last_Fin,
- Build_Raise_Statement (Finalizer_Data));
+ Build_Raise_Statement (Fin_Data));
end if;
end Process_Transient_Objects;
