Range check error while evaluating constants

[LemonParty]

Hello.

Can't compile code below:

Code: Pascal  [Select][+][-]

1. {$mode objfpc}
2. {$modeswitch advancedrecords}
3.  
4. type
5.   Int24 = packed record
6.     W: Word;
7.     B: Byte;
8.     class operator :=(aA: LongInt): Int24;inline;
9.   end;
10.  
11.   class operator Int24.:=(aA: LongInt): Int24;
12.   begin
13.     Result.W:= Lo(aA);
14.     Result.B:= Hi(aA);
15.   end;
16.  
17. var
18.   i24: Int24;
19. begin
20.   i24:= -5;
21. end.
22.  

Error

Range check error while evaluating constants (281474976710655 must be between 0 and 65535)

What I missing?

[ASerge]

A workaround:

Code: Pascal  [Select][+][-]

1.   class operator Int24. := (aA: LongInt): Int24;
2.   var
3.     bB: LongWord absolute aA;
4.   begin
5.     Result.W:= Lo(bB);
6.     Result.B:= Hi(Hi(bB));
7.   end;

[Nitorami]

What I don't understand here is how the compiler gets to 281474976710655 = $FFFF FFFF FFFF ?

[jamie]

I thinking this is what he needs to do with the original code.

Code: Pascal  [Select][+][-]

1. program Project1;
2.  
3. {$mode objfpc}{$H+}
4. {$modeswitch advancedrecords}
5.  
6. type
7.   Int24 = packed record
8.     W: Word;
9.     B: Byte;
10.     class operator :=(aA: LongInt): Int24;inline;
11.   end;
12.  
13.   class operator Int24.:=(aA: LongInt): Int24;
14.   begin
15.     Result.W:= Lo(aA);
16.     Result.B:= Lo(Word(aA shr 16)); // fixed here.
17.   end;
18.  
19. var
20.   i24: Int24;
21. begin
22.   i24:= -5;
23. end.                        
24.  
25.  

@Serge:
  neat trick, never thought of using double HI.

Jamie

[jamie]

@Aserge
shouldn't it be like this?

Code: Pascal  [Select][+][-]

1.   class operator Int24.:=(aA: LongInt): Int24;
2.   begin
3.     Result.W:= Lo(aA);
4.     Result.B:= Lo(Hi(LongWord(aA)));
5.   end;
6.                                                
7.  

I would think the upper byte would be at the lower end unless we are doing Big Endian?

Jamie

[jamie]

I see the issue now.

You need to set the upper bit of the Byte to what is was originally so the (-) flag will carry over.

so like this..

If aA < 0 Then B := B or $80 else B:=B and $7F;

that should be done after the mov.

Code: Pascal  [Select][+][-]

1.  class operator Int24.:=(aA: LongInt): Int24;
2.   begin
3.      Result.W:= Lo(aA);
4.      Result.B:= Lo(Hi(LongWord(aA)));
5.      If aA <0 Then result.B := Result.B or $80 else
6.         Result.B := Result.B and $7F;
7.   end;                          
8.  
9.  

Something like that.

[Thaddy]

You can also just declare the byte as shortint (-128..127) because that is what you mean with a signed type.
I think :

Code: Pascal  [Select][+][-]

1. {$mode objfpc}{$modeswitch advancedrecords}
2. type
3.   Int24 = packed record
4.     B: shortint;// msb+sign
5.     W: Word;    // lsw
6.     class operator :=(const aA: LongInt): Int24;inline;
7.     class operator :=(const aA: Int24): longint;inline;
8.  end;
9.  
10.   class operator Int24.:=(const aA: LongInt): Int24;
11.   begin
12.     Result.W:= Lo(aA);
13.     Result.B:= shortint(aA shr 24);//preserves sign
14.   end;
15.  
16.   class operator Int24.:=(const aA: Int24): longint;inline;
17.   begin
18.     Result:=aA.b shl 16 + aA.w;
19.   end;
20.  
21. var
22.   i24: Int24;
23.   i:integer;
24. begin
25.   i24:= -5;
26.   i := i24;
27.   writeln(i);
28. end.

[LemonParty]

Thank you for answers.
I discovered that this solution is also working:

Code: Pascal  [Select][+][-]

1.   class operator Int24.:=(aA: LongInt): Int24;
2.   begin
3.     Result.W:= Lo(DWord(aA));
4.     Result.B:= Hi(DWord(aA));
5.   end;
6.  

[Thaddy]

And where's the sign? Doesn't work here without warnings.

[LemonParty]

No warning in this case:

Code: Pascal  [Select][+][-]

1.   class operator Int24.:=(constref aA: LongInt): Int24;
2.   begin
3.     Result.W:= Lo(DWord(aA));
4.     Result.B:= Byte(Hi(DWord(aA)));
5.   end;
6.  

Sign is saved.

[jamie]

I doubt the sign bit is saved.

Look at my last post.

You at least need to put a range check on the incoming integer;
Jamie

[LemonParty]

I consider that incoming Longint is in range of 24-bit integer. In this case sign is OK. Extending integer is needed in opposite situation if we for example converting from Int16 to Int24.

[jamie]

Do as you please, but you won't be happen when your code starts entering integer values larger than 12 bit and you don't check for that.

The MSByte of the 32-bit incoming should be $FF or $00 for a valid 24bit value.

Have a good day and may your bugs be many!

Jamie

[creaothceann]

Code: Pascal  [Select][+][-]

1. {$mode ObjFPC}
2. {$ModeSwitch AdvancedRecords}
3.  
4. {$ifdef ENDIAN_BIG}
5.         {$fatal}
6. {$endif}
7.  
8. interface
9.  
10. const Bit0  = 1 SHL  0;  Bits0  = Bit0  - 1;
11. const Bit1  = 1 SHL  1;  Bits1  = Bit1  - 1;    type u1  = 0..Bits0;   i1  = -Bit0 ..Bits0;
12. const Bit2  = 1 SHL  2;  Bits2  = Bit2  - 1;    type u2  = 0..Bits1;   i2  = -Bit1 ..Bits1;
13. const Bit3  = 1 SHL  3;  Bits3  = Bit3  - 1;    type u3  = 0..Bits2;   i3  = -Bit2 ..Bits2;
14. const Bit4  = 1 SHL  4;  Bits4  = Bit4  - 1;    type u4  = 0..Bits3;   i4  = -Bit3 ..Bits3;
15. const Bit5  = 1 SHL  5;  Bits5  = Bit5  - 1;    type u5  = 0..Bits4;   i5  = -Bit4 ..Bits4;
16. const Bit6  = 1 SHL  6;  Bits6  = Bit6  - 1;    type u6  = 0..Bits5;   i6  = -Bit5 ..Bits5;
17. const Bit7  = 1 SHL  7;  Bits7  = Bit7  - 1;    type u7  = 0..Bits6;   i7  = -Bit6 ..Bits6;
18. const Bit8  = 1 SHL  8;  Bits8  = Bit8  - 1;    type u8  = 0..Bits8;   i8  = -Bit7 ..Bits7;
19. const Bit9  = 1 SHL  9;  Bits9  = Bit9  - 1;    type u9  = 0..Bits9;   i9  = -Bit8 ..Bits8;
20. const Bit10 = 1 SHL 10;  Bits10 = Bit10 - 1;    type u10 = 0..Bits10;  i10 = -Bit9 ..Bits9;
21. const Bit11 = 1 SHL 11;  Bits11 = Bit11 - 1;    type u11 = 0..Bits11;  i11 = -Bit10..Bits10;
22. const Bit12 = 1 SHL 12;  Bits12 = Bit12 - 1;    type u12 = 0..Bits12;  i12 = -Bit11..Bits11;
23. const Bit13 = 1 SHL 13;  Bits13 = Bit13 - 1;    type u13 = 0..Bits13;  i13 = -Bit12..Bits12;
24. const Bit14 = 1 SHL 14;  Bits14 = Bit14 - 1;    type u14 = 0..Bits14;  i14 = -Bit13..Bits13;
25. const Bit15 = 1 SHL 15;  Bits15 = Bit15 - 1;    type u15 = 0..Bits15;  i15 = -Bit14..Bits14;
26. const Bit16 = 1 SHL 16;  Bits16 = Bit16 - 1;    type u16 = 0..Bits16;  i16 = -Bit15..Bits15;
27. const Bit17 = 1 SHL 17;  Bits17 = Bit17 - 1;    type u17 = 0..Bits17;  i17 = -Bit16..Bits16;
28. const Bit18 = 1 SHL 18;  Bits18 = Bit18 - 1;    type u18 = 0..Bits18;  i18 = -Bit17..Bits17;
29. const Bit19 = 1 SHL 19;  Bits19 = Bit19 - 1;    type u19 = 0..Bits19;  i19 = -Bit18..Bits18;
30. const Bit20 = 1 SHL 20;  Bits20 = Bit20 - 1;    type u20 = 0..Bits20;  i20 = -Bit19..Bits19;
31. const Bit21 = 1 SHL 21;  Bits21 = Bit21 - 1;    type u21 = 0..Bits21;  i21 = -Bit20..Bits20;
32. const Bit22 = 1 SHL 22;  Bits22 = Bit22 - 1;    type u22 = 0..Bits22;  i22 = -Bit21..Bits21;
33. const Bit23 = 1 SHL 23;  Bits23 = Bit23 - 1;    type u23 = 0..Bits23;  i23 = -Bit22..Bits22;
34. const Bit24 = 1 SHL 24;  Bits24 = Bit24 - 1;    type u24 = 0..Bits24;  i24 = -Bit23..Bits23;
35. const Bit25 = 1 SHL 25;  Bits25 = Bit25 - 1;    type u25 = 0..Bits25;  i25 = -Bit24..Bits24;
36. const Bit26 = 1 SHL 26;  Bits26 = Bit26 - 1;    type u26 = 0..Bits26;  i26 = -Bit25..Bits25;
37. const Bit27 = 1 SHL 27;  Bits27 = Bit27 - 1;    type u27 = 0..Bits27;  i27 = -Bit26..Bits26;
38. const Bit28 = 1 SHL 28;  Bits28 = Bit28 - 1;    type u28 = 0..Bits28;  i28 = -Bit27..Bits27;
39. const Bit29 = 1 SHL 29;  Bits29 = Bit29 - 1;    type u29 = 0..Bits29;  i29 = -Bit28..Bits28;
40. const Bit30 = 1 SHL 30;  Bits30 = Bit30 - 1;    type u30 = 0..Bits30;  i30 = -Bit29..Bits29;
41. const Bit31 = 1 SHL 31;  Bits31 = Bit31 - 1;    type u31 = 0..Bits31;  i31 = -Bit30..Bits30;
42. const Bit32 = 1 SHL 32;  Bits32 = Bit32 - 1;    type u32 = 0..Bits32;  i32 = -Bit31..Bits31;  uint = u32;  int = int32;
43.  
44.  
45. type
46.         Int24 = packed record
47.                 L : u16;
48.                 H : u8;
49.  
50.                 class operator :=(const Value : i32) : Int24;  inline;
51.                 end;
52.  
53.  
54. implementation
55.  
56.  
57. type
58.         u32_record = packed record
59.                 case uint of
60.                         0: (b0, b1, b2, b3 : u8 );
61.                         1: (w0,     w1     : u16);
62.                         2: (d0             : u32);
63.                 end;
64.  
65.  
66. class operator Int24.:=(const Value : i32) : Int24;  inline;
67. var
68.         v : u32_record absolute Value;
69. begin
70.         Assert(     v.b3 in [$00, $FF]);
71.         Result.L := v.w0;
72.         Result.H := v.b2;
73. end;
74.  
75.  
76. var
77.         tmp_i24 : Int24;
78.  
79.  
80. begin
81.         tmp_i24 := -5;
82. end.
83.