[PB 5.60] Label arithmetic bug

[kenmo]

I thought this was posted before, but I don't see it.

Subtracting two label addresses, in argument to Round(), causes strange result.
Subtracting two pointer variables is OK.
You can remove the /4, issue remains.

PB 5.60 x86 Windows 7

Code: Select all

DataSection
  Start:
  Data.a $01, $02, $03, $04    ; 4 bytes (1 long)
  Finish:
EndDataSection

nBytes = (?Finish - ?Start)
;Debug nBytes ; OK (4)

nLongs = nBytes / 4
Debug nLongs ; OK (1)

nLongs = (?Finish - ?Start) / 4
Debug nLongs ; OK (1)

nLongs = Round(nBytes / 4, #PB_Round_Up)
Debug nLongs ; OK (1)

nLongs = Round((?Finish - ?Start) / 4, #PB_Round_Up) ; <------------------------
Debug nLongs ; not OK!

*Start  = ?Start
*Finish = ?Finish

nLongs = Round((*Finish - *Start) / 4, #PB_Round_Up)
Debug nLongs ; OK (1)

[User_Russian]

Not only Round

Code: Select all

DataSection
  Start:
  Data.a $01, $02, $03, $04    ; 4 bytes (1 long)
  Finish:
EndDataSection

nBytes = (?Finish - ?Start)
;Debug nBytes ; OK (4)

nLongs = nBytes / 4
Debug nLongs ; OK (1)

nLongs = (?Finish - ?Start) / 4
Debug nLongs ; OK (1)

nLongs = Round(nBytes / 4, #PB_Round_Up)
Debug nLongs ; OK (1)

nLongs = Round((?Finish - ?Start), #PB_Round_Up) ; <------------------------
Debug nLongs ; not OK!

nLongs = Int((?Finish - ?Start)) ; <------------------------
Debug nLongs ; not OK!

nLongs = Pow((?Finish - ?Start), 1) ; <------------------------
Debug nLongs ; not OK!

s.s = StrF((?Finish - ?Start)) ; <------------------------
Debug s ; not OK!

This is because of the conversion to a floating-point number.

Code: Select all

DataSection
  Start:
  Data.a $01, $02, $03, $04    ; 4 bytes (1 long)
  Finish:
EndDataSection

x.f=(?Finish - ?Start)
Debug x

[Fred]

Yes, round() is for floating point, so it won't work with addresses.

[kenmo]

Yes, round() is for floating point, so it won't work with addresses.

Hi Fred. Even if you don't call any float functions, it looks like a bug with address --> float arithmetic.

Code: Select all

DataSection
  Start:
  Data.b $01, $02, $03, $04    ; 4 bytes (1 long)
  Finish:
EndDataSection

 Start  = ?Start
 Finish = ?Finish
*Start  = ?Start
*Finish = ?Finish

Debug       ( Finish -  Start) * 1.5      ;  (int - int) * float
Debug 1.5 * ( Finish -  Start)            ;  float * (int - int)

Debug       (*Finish - *Start) * 1.5      ;  (int - int) * float
Debug 1.5 * (*Finish - *Start)            ;  float * (int - int)

Debug       (?Finish - ?Start) * 1.5      ;  (int - int) * float
Debug 1.5 * (?Finish - ?Start)            ;  float * (int - int)

This could cause strange memory bugs!

Code: Select all

DataSection
  Start:
  Data.b $01, $02, $03, $04    ; 4 bytes (1 long)
  Finish:
EndDataSection

BufferSize.i = 1.5 * (?Finish - ?Start)
Debug BufferSize

BufferSize.i = (?Finish - ?Start) * 1.5
Debug BufferSize

BufferSize.i = 1.5 * (?Finish - ?Start)
Debug BufferSize

[skywalk]

This should be mentioned in the manual. Since type casting is dependent on algebraic order, it should be noted that pointers/labels are also type cast with unintended results.
The fix is assign pointers' integer values prior to using in algebra.