===================================================================
@@ -6,7 +6,7 @@
-- --
-- B o d y --
-- --
+-- Copyright (C) 1992-2015, 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- --
@@ -5521,10 +5521,14 @@
return;
end if;
- -- Ditto if the prefix is an explicit dereference whose designated
- -- type is unconstrained.
+ -- Ditto if prefix is simply an unconstrained array. We used
+ -- to think this case was OK, if the prefix was not an explicit
+ -- dereference, but we have now seen a case where this is not
+ -- true, so it is safer to just suppress the optimization in this
+ -- case. The back end is getting better at eliminating redundant
+ -- checks in any case, so the loss won't be important.
- elsif Nkind (Prefix (P)) = N_Explicit_Dereference
+ elsif Is_Array_Type (Atyp)
and then not Is_Constrained (Atyp)
then
Activate_Range_Check (N);
In some unusual cases, the index check on a subscript of an unconstrained array was omitted. The following test program 1. package Out_Constraint_Violation is 2. type Arr is array (Natural range <>) of Integer; 3. procedure Violate 4. (Input : Arr; Modifier : Arr; Output: out Arr); 5. end Out_Constraint_Violation; 1. package body Out_Constraint_Violation is 2. procedure Violate 3. (Input : Arr; Modifier : Arr; Output: out Arr) is 4. begin 5. for J in Input'Range loop 6. -- For the error to occur, 7. -- we need to have a declare block ... 8. declare 9. -- ... with at least this level of complexity. 10. Product : constant Integer := Modifier (J); 11. begin 12. Output (J) := Product / 2; 13. end; 14. end loop; 15. end Violate; 16. end Out_Constraint_Violation; 1. with Ada.Text_IO; use Ada.Text_IO; 2. procedure Out_Constraint_Violation.Main is 3. Size : constant := 10; 4. Input : Arr (1 .. Size) := (others => 128); 5. Modifier : Arr (1 .. Size) := (others => 128); 6. Output : Arr (1 .. Size + 1) := (others => 42); 7. begin 8. Violate (Input, Modifier, Output (1 .. Size - 1)); 9. Put_Line ("Size:" & Integer'Image (Size)); 10. for L in Size - 1 .. Size + 1 loop 11. Put_Line ("Output(" & L'Img & "):" & 12. Output (L)'Img); 13. end loop; 14. end Out_Constraint_Violation.Main; If compiled with -O should raise CE at run time: raised CONSTRAINT_ERROR : out_constraint_violation.adb:12 index check failed Tested on x86_64-pc-linux-gnu, committed on trunk 2015-02-05 Robert Dewar <dewar@adacore.com> * checks.adb (Enable_Range_Check): Disconnect attempted optimization for the case of range check for subscript of unconstrained array.