exp_ch5.adb, [...]: Minor comment correction.

2014-07-31  Robert Dewar  <dewar@adacore.com>

	* exp_ch5.adb, freeze.adb, exp_ch3.adb: Minor comment correction.
	* s-arit64.adb: Minor reformatting.

2014-07-31  Robert Dewar  <dewar@adacore.com>

	* gnat1drv.adb (Adjust_Global_Switches): Default for overflow
	checking is enabled except in GNAT_Mode.
	* switch-c.adb (Scan_Front_End_Switches): Implement -gnato0
	(suppress overflow checks).

From-SVN: r213327

gcc/ada/ChangeLog

+2014-07-31  Robert Dewar  <dewar@adacore.com>
+
+	* exp_ch5.adb, freeze.adb, exp_ch3.adb: Minor comment correction.
+	* s-arit64.adb: Minor reformatting.
+
+2014-07-31  Robert Dewar  <dewar@adacore.com>
+
+	* gnat1drv.adb (Adjust_Global_Switches): Default for overflow
+	checking is enabled except in GNAT_Mode.
+	* switch-c.adb (Scan_Front_End_Switches): Implement -gnato0
+	(suppress overflow checks).
+
 2014-07-31  Ed Schonberg  <schonberg@adacore.com>
 
 	* exp_ch3.adb (Expand_Freeze_Record_Type): Do not build an

gcc/ada/exp_ch3.adb

@@ -1752,7 +1752,7 @@ package body Exp_Ch3 is
       --  objects on list Decls.
 
       function Build_Init_Call_Thru (Parameters : List_Id) return List_Id;
-      --  Given a untagged type-derivation that declares discriminants, e.g.
+      --  Given an untagged type-derivation that declares discriminants, e.g.
       --
       --     type R (R1, R2 : Integer) is record ... end record;
       --     type D (D1 : Integer) is new R (1, D1);
@@ -5838,7 +5838,7 @@ package body Exp_Ch3 is
 
             --  Handle C++ constructor calls. Note that we do not check that
             --  Typ is a tagged type since the equivalent Ada type of a C++
-            --  class that has no virtual methods is a untagged limited
+            --  class that has no virtual methods is an untagged limited
             --  record type.
 
             elsif Is_CPP_Constructor_Call (Expr) then

gcc/ada/exp_ch5.adb

@@ -106,7 +106,7 @@ package body Exp_Ch5 is
    --  using the standard Insert_Actions mechanism.
 
    procedure Expand_Assign_Record (N : Node_Id);
-   --  N is an assignment of a untagged record value. This routine handles
+   --  N is an assignment of an untagged record value. This routine handles
    --  the case where the assignment must be made component by component,
    --  either because the target is not byte aligned, or there is a change
    --  of representation, or when we have a tagged type with a representation

gcc/ada/freeze.adb

@@ -4537,8 +4537,8 @@ package body Freeze is
             return No_List;
          end if;
 
-         --  Check for error of Type_Invariant'Class applied to a untagged type
-         --  (check delayed to freeze time when full type is available).
+         --  Check for error of Type_Invariant'Class applied to an untagged
+         --  type (check delayed to freeze time when full type is available).
 
          declare
             Prag : constant Node_Id := Get_Pragma (E, Pragma_Invariant);

gcc/ada/gnat1drv.adb

@@ -511,9 +511,13 @@ procedure Gnat1drv is
       --  Otherwise set overflow mode defaults
 
       else
-         --  Otherwise set overflow checks off by default
+         --  Overflow checks are on by default (Suppress set False) except in
+         --  GNAT_Mode, where we want them off by default (we are not ready to
+         --  enable overflow checks in the compiler yet, for one thing the case
+         --  of 64-bit checks needs System.Arith_64 which is not a compiler
+         --  unit and it is a pain to try to include it in the compiler.
 
-         Suppress_Options.Suppress (Overflow_Check) := True;
+         Suppress_Options.Suppress (Overflow_Check) := GNAT_Mode;
 
          --  Set appropriate default overflow handling mode. Note: at present
          --  we set STRICT in all three of the following cases. They are
@@ -531,8 +535,8 @@ procedure Gnat1drv is
          --  flags set, so this was dead code anyway.
 
          elsif Targparm.Backend_Divide_Checks_On_Target
-           and
-             Targparm.Backend_Overflow_Checks_On_Target
+                 and
+               Targparm.Backend_Overflow_Checks_On_Target
          then
             Suppress_Options.Overflow_Mode_General    := Strict;
             Suppress_Options.Overflow_Mode_Assertions := Strict;

gcc/ada/s-arit64.adb

@@ -259,8 +259,8 @@ package body System.Arith_64 is
          T2 := 0;
       end if;
 
-      --  Here we have T2 set to the contribution to the upper half
-      --  of the result from the upper halves of the input values.
+      --  Here we have T2 set to the contribution to the upper half of the
+      --  result from the upper halves of the input values.
 
       T1 := Xlo * Ylo;
       T2 := T2 + Hi (T1);
@@ -332,9 +332,9 @@ package body System.Arith_64 is
 
       Scale : Natural;
       --  Scaling factor used for multiple-precision divide. Dividend and
-      --  Divisor are multiplied by 2 ** Scale, and the final remainder
-      --  is divided by the scaling factor. The reason for this scaling
-      --  is to allow more accurate estimation of quotient digits.
+      --  Divisor are multiplied by 2 ** Scale, and the final remainder is
+      --  divided by the scaling factor. The reason for this scaling is to
+      --  allow more accurate estimation of quotient digits.
 
       T1, T2, T3 : Uns64;
       --  Temporary values
@@ -383,8 +383,8 @@ package body System.Arith_64 is
          D (1) := 0;
       end if;
 
-      --  Now it is time for the dreaded multiple precision division. First
-      --  an easy case, check for the simple case of a one digit divisor.
+      --  Now it is time for the dreaded multiple precision division. First an
+      --  easy case, check for the simple case of a one digit divisor.
 
       if Zhi = 0 then
          if D (1) /= 0 or else D (2) >= Zlo then

gcc/ada/switch-c.adb

@@ -953,38 +953,57 @@ package body Switch.C is
 
             when 'o' =>
                Ptr := Ptr + 1;
-               Suppress_Options.Suppress (Overflow_Check) := False;
 
-               --  Case of no digits after the -gnato
+               --  Case of -gnato0 (overflow checking turned off)
+
+               if Ptr <= Max and then Switch_Chars (Ptr) = '0' then
+                  Ptr := Ptr + 1;
+                  Suppress_Options.Suppress (Overflow_Check) := True;
+
+                  --  We set strict mode in case overflow checking is turned
+                  --  on locally (also records that we had a -gnato switch).
 
-               if Ptr > Max or else Switch_Chars (Ptr) not in '1' .. '3' then
                   Suppress_Options.Overflow_Mode_General    := Strict;
                   Suppress_Options.Overflow_Mode_Assertions := Strict;
 
-               --  At least one digit after the -gnato
+               --  All cases other than -gnato0 (overflow checking turned on)
 
                else
-                  --  Handle first digit after -gnato
-
-                  Suppress_Options.Overflow_Mode_General :=
-                    Get_Overflow_Mode (Switch_Chars (Ptr));
-                  Ptr := Ptr + 1;
+                  Suppress_Options.Suppress (Overflow_Check) := False;
 
-                  --  Only one digit after -gnato, set assertions mode to
-                  --  be the same as general mode.
+                  --  Case of no digits after the -gnato
 
                   if Ptr > Max
                     or else Switch_Chars (Ptr) not in '1' .. '3'
                   then
-                     Suppress_Options.Overflow_Mode_Assertions :=
-                       Suppress_Options.Overflow_Mode_General;
+                     Suppress_Options.Overflow_Mode_General    := Strict;
+                     Suppress_Options.Overflow_Mode_Assertions := Strict;
 
-                  --  Process second digit after -gnato
+                  --  At least one digit after the -gnato
 
                   else
-                     Suppress_Options.Overflow_Mode_Assertions :=
+                     --  Handle first digit after -gnato
+
+                     Suppress_Options.Overflow_Mode_General :=
                        Get_Overflow_Mode (Switch_Chars (Ptr));
                      Ptr := Ptr + 1;
+
+                     --  Only one digit after -gnato, set assertions mode to be
+                     --  the same as general mode.
+
+                     if Ptr > Max
+                       or else Switch_Chars (Ptr) not in '1' .. '3'
+                     then
+                        Suppress_Options.Overflow_Mode_Assertions :=
+                          Suppress_Options.Overflow_Mode_General;
+
+                     --  Process second digit after -gnato
+
+                     else
+                        Suppress_Options.Overflow_Mode_Assertions :=
+                          Get_Overflow_Mode (Switch_Chars (Ptr));
+                        Ptr := Ptr + 1;
+                     end if;
                   end if;
                end if;
 
@@ -1026,6 +1045,13 @@ package body Switch.C is
 
                   Validity_Checks_On  := False;
                   Opt.Suppress_Checks := True;
+
+                  --  Set overflow mode checking to strict in case it gets
+                  --  turned on locally (also signals that overflow checking
+                  --  has been specifically turned off).
+
+                  Suppress_Options.Overflow_Mode_General    := Strict;
+                  Suppress_Options.Overflow_Mode_Assertions := Strict;
                end if;
 
             --  -gnatP (periodic poll)