[Ada] Fix missing index check with optimization on

[Arnaud Charlet <charlet at adacore dot com>]

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.

Attachment: difs
Description: Text document