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# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.

from __future__ import absolute_import, division, print_function

INCLUDES = """
#include <CoreFoundation/CoreFoundation.h>
"""

TYPES = """
typedef bool Boolean;
typedef signed long OSStatus;
typedef unsigned char UInt8;
typedef uint32_t UInt32;

typedef const void * CFAllocatorRef;
const CFAllocatorRef kCFAllocatorDefault;
typedef ... *CFDataRef;
typedef signed long long CFIndex;
typedef ... *CFStringRef;
typedef ... *CFArrayRef;
typedef ... *CFMutableArrayRef;
typedef ... *CFBooleanRef;
typedef ... *CFErrorRef;
typedef ... *CFNumberRef;
typedef ... *CFTypeRef;
typedef ... *CFDictionaryRef;
typedef ... *CFMutableDictionaryRef;
typedef struct {
    ...;
} CFDictionaryKeyCallBacks;
typedef struct {
    ...;
} CFDictionaryValueCallBacks;
typedef struct {
    ...;
} CFRange;
typedef struct {
    ...;
} CFArrayCallBacks;

typedef UInt32 CFStringEncoding;
enum {
    kCFStringEncodingASCII = 0x0600
};

enum {
   kCFNumberSInt8Type = 1,
   kCFNumberSInt16Type = 2,
   kCFNumberSInt32Type = 3,
   kCFNumberSInt64Type = 4,
   kCFNumberFloat32Type = 5,
   kCFNumberFloat64Type = 6,
   kCFNumberCharType = 7,
   kCFNumberShortType = 8,
   kCFNumberIntType = 9,
   kCFNumberLongType = 10,
   kCFNumberLongLongType = 11,
   kCFNumberFloatType = 12,
   kCFNumberDoubleType = 13,
   kCFNumberCFIndexType = 14,
   kCFNumberNSIntegerType = 15,
   kCFNumberCGFloatType = 16,
   kCFNumberMaxType = 16
};
typedef int CFNumberType;

const CFDictionaryKeyCallBacks kCFTypeDictionaryKeyCallBacks;
const CFDictionaryValueCallBacks kCFTypeDictionaryValueCallBacks;

const CFArrayCallBacks kCFTypeArrayCallBacks;

const CFBooleanRef kCFBooleanTrue;
const CFBooleanRef kCFBooleanFalse;
"""

FUNCTIONS = """
CFDataRef CFDataCreate(CFAllocatorRef, const UInt8 *, CFIndex);
CFStringRef CFStringCreateWithCString(CFAllocatorRef, const char *,
                                      CFStringEncoding);
CFDictionaryRef CFDictionaryCreate(CFAllocatorRef, const void **,
                                   const void **, CFIndex,
                                   const CFDictionaryKeyCallBacks *,
                                   const CFDictionaryValueCallBacks *);
CFMutableDictionaryRef CFDictionaryCreateMutable(
    CFAllocatorRef,
    CFIndex,
    const CFDictionaryKeyCallBacks *,
    const CFDictionaryValueCallBacks *
);
void CFDictionarySetValue(CFMutableDictionaryRef, const void *, const void *);
CFIndex CFArrayGetCount(CFArrayRef);
const void *CFArrayGetValueAtIndex(CFArrayRef, CFIndex);
CFIndex CFDataGetLength(CFDataRef);
void CFDataGetBytes(CFDataRef, CFRange, UInt8 *);
CFRange CFRangeMake(CFIndex, CFIndex);
void CFShow(CFTypeRef);
Boolean CFBooleanGetValue(CFBooleanRef);
CFNumberRef CFNumberCreate(CFAllocatorRef, CFNumberType, const void *);
void CFRelease(CFTypeRef);
CFTypeRef CFRetain(CFTypeRef);

CFMutableArrayRef CFArrayCreateMutable(CFAllocatorRef, CFIndex,
                                       const CFArrayCallBacks *);
void CFArrayAppendValue(CFMutableArrayRef, const void *);
"""

MACROS = """
"""

CUSTOMIZATIONS = """
"""
ref='#n471'>471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651
--  Lexical analysis for numbers.
--  Copyright (C) 2002 - 2014 Tristan Gingold
--
--  GHDL is free software; you can redistribute it and/or modify it under
--  the terms of the GNU General Public License as published by the Free
--  Software Foundation; either version 2, or (at your option) any later
--  version.
--
--  GHDL is distributed in the hope that it will be useful, but WITHOUT ANY
--  WARRANTY; without even the implied warranty of MERCHANTABILITY or
--  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
--  for more details.
--
--  You should have received a copy of the GNU General Public License
--  along with GHDL; see the file COPYING.  If not, write to the Free
--  Software Foundation, 59 Temple Place - Suite 330, Boston, MA
--  02111-1307, USA.
with Ada.Unchecked_Conversion;

separate (Scanner)

-- scan a decimal literal or a based literal.
--
-- LRM93 13.4.1
-- DECIMAL_LITERAL ::= INTEGER [ . INTEGER ] [ EXPONENT ]
-- EXPONENT ::= E [ + ] INTEGER | E - INTEGER
--
-- LRM93 13.4.2
-- BASED_LITERAL ::= BASE # BASED_INTEGER [ . BASED_INTEGER ] # EXPONENT
-- BASE ::= INTEGER
procedure Scan_Literal is
   --  The base of an E_NUM is 2**16.
   --  Type Uint16 is the type of a digit.
   type Uint16 is mod 2 ** 16;

   type Uint32 is mod 2 ** 32;

   --  Type of the exponent.
   type Sint16 is range -2 ** 15 .. 2 ** 15 - 1;

   --  Number of digits in a E_NUM.
   --  We want at least 64bits of precision, so at least 5 digits of 16 bits
   --  are required.
   Nbr_Digits : constant Sint16 := 5;
   subtype Digit_Range is Sint16 range 0 .. Nbr_Digits - 1;

   type Uint16_Array is array (Sint16 range <>) of Uint16;

   --  The value of an E_NUM is (S(N-1)|S(N-2) .. |S(0))* 2**(16*E)
   --  where '|' is concatenation.
   type E_Num is record
      S : Uint16_Array (Digit_Range);
      E : Sint16;
   end record;

   E_Zero : constant E_Num := (S => (others => 0), E => 0);
   E_One  : constant E_Num := (S => (0 => 1, others => 0), E => 0);

   --  Compute RES = E * B + V.
   --  RES and E can be the same object.
   procedure Bmul (Res : out E_Num; E : E_Num; V : Uint16; B : Uint16);

   --  Convert to integer.
   procedure Fix (Res : out Iir_Int64; Ok : out Boolean; E : E_Num);

   --  RES := A * B
   --  RES can be A or B.
   procedure Mul (Res : out E_Num; A, B : E_Num);

   --  RES := A / B.
   --  RES can be A.
   --  May raise constraint error.
   procedure Div (Res : out E_Num; A, B: E_Num);

   --  Convert V to an E_Num.
   function To_E_Num (V : Uint16) return E_Num;

   --  Convert E to RES.
   procedure To_Float (Res : out Iir_Fp64; Ok : out Boolean; E : E_Num);

   procedure Bmul (Res : out E_Num; E : E_Num; V : Uint16; B : Uint16)
   is
      --  The carry.
      C : Uint32;
   begin
      --  Only consider V if E is not scaled (otherwise V is not significant).
      if E.E = 0 then
         C := Uint32 (V);
      else
         C := 0;
      end if;

      --  Multiply and propagate the carry.
      for I in Digit_Range loop
         C := Uint32 (E.S (I)) * Uint32 (B) + C;
         Res.S (I) := Uint16 (C mod Uint16'Modulus);
         C := C / Uint16'Modulus;
      end loop;

      --  There is a carry, shift.
      if C /= 0 then
         --  ERR: Possible overflow.
         Res.E := E.E + 1;
         for I in 0 .. Nbr_Digits - 2 loop
            Res.S (I) := Res.S (I + 1);
         end loop;
         Res.S (Nbr_Digits - 1) := Uint16 (C);
      else
         Res.E := E.E;
      end if;
   end Bmul;

   type Uint64 is mod 2 ** 64;
   function Shift_Left (Value : Uint64; Amount: Natural) return Uint64;
   function Shift_Left (Value : Uint16; Amount: Natural) return Uint16;
   pragma Import (Intrinsic, Shift_Left);

   function Shift_Right (Value : Uint16; Amount: Natural) return Uint16;
   pragma Import (Intrinsic, Shift_Right);

   function Unchecked_Conversion is new Ada.Unchecked_Conversion
     (Source => Uint64, Target => Iir_Int64);

   procedure Fix (Res : out Iir_Int64; Ok : out Boolean; E : E_Num)
   is
      R : Uint64;
      M : Sint16;
   begin
      --  Find the most significant digit.
      M := -1;
      for I in reverse Digit_Range loop
         if E.S (I) /= 0 then
            M := I;
            exit;
         end if;
      end loop;

      --  Handle the easy 0 case.
      --  The case M = -1 is handled below, in the normal flow.
      if M + E.E < 0 then
         Res := 0;
         Ok := True;
         return;
      end if;

      --  Handle overflow.
      --  4 is the number of uint16 in a uint64.
      if M + E.E >= 4 then
         Ok := False;
         return;
      end if;

      --  Convert
      R := 0;
      for I in 0 .. M loop
         R := R or Shift_Left (Uint64 (E.S (I)), 16 * Natural (E.E + I));
      end loop;
      --  Check the sign bit is 0.
      if (R and Shift_Left (1, 63)) /= 0 then
         Ok := False;
      else
         Ok := True;
         Res := Unchecked_Conversion (R);
      end if;
   end Fix;

   --  Return the position of the most non-null digit, -1 if V is 0.
   function First_Digit (V : E_Num) return Sint16 is
   begin
      for I in reverse Digit_Range loop
         if V.S (I) /= 0 then
            return I;
         end if;
      end loop;
      return -1;
   end First_Digit;

   procedure Mul (Res : out E_Num; A, B : E_Num)
   is
      T : Uint16_Array (0 .. 2 * Nbr_Digits - 1);
      V : Uint32;
      Max : Sint16;
   begin
      V := 0;
      for I in 0 .. Nbr_Digits - 1 loop
         for J in 0 .. I loop
            V := V + Uint32 (A.S (J)) * Uint32 (B.S (I - J));
         end loop;
         T (I) := Uint16 (V mod Uint16'Modulus);
         V := V / Uint16'Modulus;
      end loop;
      for I in Nbr_Digits .. 2 * Nbr_Digits - 2 loop
         for J in I - Nbr_Digits + 1 .. Nbr_Digits - 1 loop
            V := V + Uint32 (A.S (J)) * Uint32 (B.S (I - J));
         end loop;
         T (I) := Uint16 (V mod Uint16'Modulus);
         V := V / Uint16'Modulus;
      end loop;
      T (T'Last) := Uint16 (V);
      --  Search the leading non-nul.
      Max := -1;
      for I in reverse T'Range loop
         if T (I) /= 0 then
            Max := I;
            exit;
         end if;
      end loop;
      if Max > Nbr_Digits - 1 then
         --  Loss of precision.
         --  Round.
         if T (Max - Nbr_Digits) >= Uint16 (Uint16'Modulus / 2) then
            V := 1;
            for I in Max - (Nbr_Digits - 1) .. Max loop
               V := V + Uint32 (T (I));
               T (I) := Uint16 (V mod Uint16'Modulus);
               V := V / Uint16'Modulus;
               exit when V = 0;
            end loop;
            if V /= 0 then
               Max := Max + 1;
               T (Max) := Uint16 (V);
            end if;
         end if;
         Res.S := T (Max - (Nbr_Digits - 1) .. Max);
         --  This may overflow.
         Res.E := A.E + B.E + Max - (Nbr_Digits - 1);
      else
         Res.S (0 .. Max) := T (0 .. Max);
         Res.S (Max + 1 .. Nbr_Digits - 1) := (others => 0);
         --  This may overflow.
         Res.E := A.E + B.E;
      end if;
   end Mul;

   procedure Div (Res : out E_Num; A, B: E_Num)
   is
      Dividend : Uint16_Array (0 .. Nbr_Digits);
      A_F : constant Sint16 := First_Digit (A);
      B_F : constant Sint16 := First_Digit (B);

      --  Digit corresponding to the first digit of B.
      Doff : constant Sint16 := Dividend'Last - B_F;
      Q : Uint16;
      C, N_C : Uint16;
   begin
      --  Check for division by 0.
      if B_F < 0 then
         raise Constraint_Error;
      end if;

      --  Copy and shift dividend.
      --  Bit 15 of the most significant digit of A becomes bit 0 of the
      --  most significant digit of DIVIDEND.  Therefore we are sure
      --  DIVIDEND < B (after realignment).
      C := 0;
      for K in 0 .. A_F loop
         N_C := Shift_Right (A.S (K), 15);
         Dividend (Dividend'Last - A_F - 1 + K)
           := Shift_Left (A.S (K), 1) or C;
         C := N_C;
      end loop;
      Dividend (Nbr_Digits) := C;
      Dividend (0 .. Dividend'last - 2 - A_F) := (others => 0);

      --  Algorithm is the same as division by hand.
      C := 0;
      for I in reverse Digit_Range loop
         Q := 0;
         for J in 0 .. 15 loop
            declare
               Borrow : Uint32;
               Tmp : Uint16_Array (0 .. B_F);
               V : Uint32;
               V16 : Uint16;
            begin
               --  Compute TMP := dividend - B;
               Borrow := 0;
               for K in 0 .. B_F loop
                  V := Uint32 (B.S (K)) + Borrow;
                  V16 := Uint16 (V mod Uint16'Modulus);
                  if V16 > Dividend (Doff + K) then
                     Borrow := 1;
                  else
                     Borrow := 0;
                  end if;
                  Tmp (K) := Dividend (Doff + K) - V16;
               end loop;

               --  If the last shift creates a carry, we are sure Dividend > B
               if C /= 0 then
                  Borrow := 0;
               end if;

               Q := Q * 2;
               --  Begin of : Dividend = Dividend * 2
               C := 0;
               for K in 0 .. Doff - 1 loop
                  N_C := Shift_Right (Dividend (K), 15);
                  Dividend (K) := Shift_Left (Dividend (K), 1) or C;
                  C := N_C;
               end loop;

               if Borrow = 0 then
                  --  Dividend > B
                  Q := Q + 1;
                  --  Dividend = Tmp * 2
                  --           = (Dividend - B) * 2
                  for K in Doff .. Nbr_Digits loop
                     N_C := Shift_Right (Tmp (K - Doff), 15);
                     Dividend (K) := Shift_Left (Tmp (K - Doff), 1) or C;
                     C := N_C;
                  end loop;
               else
                  --  Dividend = Dividend * 2
                  for K in Doff .. Nbr_Digits loop
                     N_C := Shift_Right (Dividend (K), 15);
                     Dividend (K) := Shift_Left (Dividend (K), 1) or C;
                     C := N_C;
                  end loop;
               end if;
            end;
         end loop;
         Res.S (I) := Q;
      end loop;
      Res.E := A.E - B.E + (A_F - B_F) - (Nbr_Digits - 1);
   end Div;

   procedure To_Float (Res : out Iir_Fp64; Ok : out Boolean; E : E_Num)
   is
      V : Iir_Fp64;
      P : Iir_Fp64;
   begin
      Res := 0.0;
      P := Iir_Fp64'Scaling (1.0, 16 * E.E);
      for I in Digit_Range loop
         V := Iir_Fp64 (E.S (I)) * P;
         P := Iir_Fp64'Scaling (P, 16);
         Res := Res + V;
      end loop;
      Ok := True;
   end To_Float;

   function To_E_Num (V : Uint16) return E_Num
   is
      Res : E_Num;
   begin
      Res.E := 0;
      Res.S := (0 => V, others => 0);
      return Res;
   end To_E_Num;

   --  Numbers of digits.
   Scale : Integer;
   Res : E_Num;

   --  LRM 13.4.1
   --  INTEGER ::= DIGIT { [ UNDERLINE ] DIGIT }
   --
   --  Update SCALE, RES.
   --  The first character must be a digit.
   procedure Scan_Integer
   is
      C : Character;
   begin
      C := Source (Pos);
      loop
         --  C is a digit.
         Bmul (Res, Res, Character'Pos (C) - Character'Pos ('0'), 10);
         Scale := Scale + 1;

         Pos := Pos + 1;
         C := Source (Pos);
         if C = '_' then
            loop
               Pos := Pos + 1;
               C := Source (Pos);
               exit when C /= '_';
               Error_Msg_Scan ("double underscore in number");
            end loop;
            if C not in '0' .. '9' then
               Error_Msg_Scan ("underscore must be followed by a digit");
            end if;
         end if;
         exit when C not in '0' .. '9';
      end loop;
   end Scan_Integer;

   C : Character;
   D : Uint16;
   Ok : Boolean;
   Has_Dot : Boolean;
   Exp : Integer;
   Exp_Neg : Boolean;
   Base : Uint16;
begin
   --  Start with a simple and fast conversion.
   C := Source (Pos);
   D := 0;
   loop
      D := D * 10 + Character'Pos (C) - Character'Pos ('0');

      Pos := Pos + 1;
      C := Source (Pos);
      if C = '_' then
         loop
            Pos := Pos + 1;
            C := Source (Pos);
            exit when C /= '_';
            Error_Msg_Scan ("double underscore in number");
         end loop;
         if C not in '0' .. '9' then
            Error_Msg_Scan ("underscore must be followed by a digit");
         end if;
      end if;
      if C not in '0' .. '9' then
         if C = '.' or else C = '#' or else (C = 'e' or C = 'E' or C = ':')
         then
            --  Continue scanning.
            Res := To_E_Num (D);
            exit;
         end if;

         --  Finished.
         --  a universal integer.
         Current_Token := Tok_Integer;
         --  No possible overflow.
         Current_Context.Int64 := Iir_Int64 (D);
         return;
      elsif D >= 6552 then
         --  Number may be greather than the uint16 limit.
         Scale := 0;
         Res := To_E_Num (D);
         Scan_Integer;
         exit;
      end if;
   end loop;

   Has_Dot := False;
   Base := 10;

   C := Source (Pos);
   if C = '.' then
      --  Decimal integer.
      Has_Dot := True;
      Scale := 0;
      Pos := Pos + 1;
      C := Source (Pos);
      if C not in '0' .. '9' then
         Error_Msg_Scan ("a dot must be followed by a digit");
         return;
      end if;
      Scan_Integer;
   elsif C = '#'
     or else (C = ':' and then (Source (Pos + 1) in '0' .. '9'
                                or else Source (Pos + 1) in 'a' .. 'f'
                                or else Source (Pos + 1) in 'A' .. 'F'))
   then
      --  LRM 13.10
      --  The number sign (#) of a based literal can be replaced by colon (:),
      --  provided that the replacement is done for both occurrences.
      -- GHDL: correctly handle 'variable v : integer range 0 to 7:= 3'.
      --   Is there any other places where a digit can be followed
      --   by a colon ? (See IR 1093).

      --  Based integer.
      declare
         Number_Sign : constant Character := C;
         Res_Int : Iir_Int64;
      begin
         Fix (Res_Int, Ok, Res);
         if not Ok or else Res_Int > 16 then
            --  LRM 13.4.2
            --  The base must be [...] at most sixteen.
            Error_Msg_Scan ("base must be at most 16");
            --  Fallback.
            Base := 16;
         elsif Res_Int < 2 then
            --  LRM 13.4.2
            --  The base must be at least two [...].
            Error_Msg_Scan ("base must be at least 2");
            --  Fallback.
            Base := 2;
         else
            Base := Uint16 (Res_Int);
         end if;

         Pos := Pos + 1;
         Res := E_Zero;
         C := Source (Pos);
         loop
            if C >= '0' and C <= '9' then
               D := Character'Pos (C) - Character'Pos ('0');
            elsif C >= 'A' and C <= 'F' then
               D := Character'Pos (C) - Character'Pos ('A') + 10;
            elsif C >= 'a' and C <= 'f' then
               D := Character'Pos (C) - Character'Pos ('a') + 10;
            else
               Error_Msg_Scan ("bad extended digit");
               exit;
            end if;

            if D >= Base then
               --  LRM 13.4.2
               --  The conventional meaning of base notation is
               --  assumed; in particular the value of each extended
               --  digit of a based literal must be less then the base.
               Error_Msg_Scan ("digit beyond base");
               D := 1;
            end if;
            Pos := Pos + 1;
            Bmul (Res, Res, D, Base);
            Scale := Scale + 1;

            C := Source (Pos);
            if C = '_' then
               loop
                  Pos := Pos + 1;
                  C := Source (Pos);
                  exit when C /= '_';
                  Error_Msg_Scan ("double underscore in based integer");
               end loop;
            elsif C = '.' then
               if Has_Dot then
                  Error_Msg_Scan ("double dot ignored");
               else
                  Has_Dot := True;
                  Scale := 0;
               end if;
               Pos := Pos + 1;
               C := Source (Pos);
            elsif C = Number_Sign then
               Pos := Pos + 1;
               exit;
            elsif C = '#' or C = ':' then
               Error_Msg_Scan ("bad number sign replacement character");
               exit;
            end if;
         end loop;
      end;
   end if;
   C := Source (Pos);
   Exp := 0;
   if C = 'E' or else C = 'e' then
      Pos := Pos + 1;
      C := Source (Pos);
      Exp_Neg := False;
      if C = '+' then
         Pos := Pos + 1;
         C := Source (Pos);
      elsif C = '-' then
         if Has_Dot then
            Exp_Neg := True;
         else
            --  LRM 13.4.1
            --  An exponent for an integer literal must not have a minus sign.
            --
            --  LRM 13.4.2
            --  An exponent for a based integer literal must not have a minus
            --  sign.
            Error_Msg_Scan
              ("negative exponent not allowed for integer literal");
         end if;
         Pos := Pos + 1;
         C := Source (Pos);
      end if;
      if C not in '0' .. '9' then
         Error_Msg_Scan ("digit expected after exponent");
      else
         loop
            --  C is a digit.
            Exp := Exp * 10 + (Character'Pos (C) - Character'Pos ('0'));

            Pos := Pos + 1;
            C := Source (Pos);
            if C = '_' then
               loop
                  Pos := Pos + 1;
                  C := Source (Pos);
                  exit when C /= '_';
                  Error_Msg_Scan ("double underscore not allowed in integer");
               end loop;
               if C not in '0' .. '9' then
                  Error_Msg_Scan ("digit expected after underscore");
                  exit;
               end if;
            elsif C not in '0' .. '9' then
               exit;
            end if;
         end loop;
      end if;
      if Exp_Neg then
         Exp := -Exp;
      end if;
   end if;

   if Has_Dot then
      Scale := Scale - Exp;
   else
      Scale := -Exp;
   end if;
   if Scale /= 0 then
      declare
         Scale_Neg : Boolean;
         Val_Exp : E_Num;
         Val_Pow : E_Num;
      begin
         if Scale > 0 then
            Scale_Neg := True;
         else
            Scale_Neg := False;
            Scale := -Scale;
         end if;

         Val_Pow := To_E_Num (Base);
         Val_Exp := E_One;
         while Scale /= 0 loop
            if Scale mod 2 = 1 then
               Mul (Val_Exp, Val_Exp, Val_Pow);
            end if;
            Scale := Scale / 2;
            Mul (Val_Pow, Val_Pow, Val_Pow);
         end loop;
         if Scale_Neg then
            Div (Res, Res, Val_Exp);
         else
            Mul (Res, Res, Val_Exp);
         end if;
      end;
   end if;

   if Has_Dot then
      -- a universal real.
      Current_Token := Tok_Real;
      -- Set to a valid literal, in case of constraint error.
      To_Float (Current_Context.Fp64, Ok, Res);
      if not Ok then
         Error_Msg_Scan ("literal beyond real bounds");
      end if;
   else
      -- a universal integer.
      Current_Token := Tok_Integer;
      -- Set to a valid literal, in case of constraint error.
      Fix (Current_Context.Int64, Ok, Res);
      if not Ok then
         Error_Msg_Scan ("literal beyond integer bounds");
      end if;
   end if;
exception
   when Constraint_Error =>
      Error_Msg_Scan ("literal overflow");
end Scan_Literal;