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[BUG/PRB.] VFP 9.0 FIX - ADJUST THE PRECISION OF THE FLOATING-POINT NUMBERS FOR THE DIVISION OPERATOR
January 2024
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CCB
1. BUG:
There is a test program:
*PROC testdivisionoperator
?STR(4/1000000,16,12) && Displays 0.000004000000
?STR(4/10000000,16,12) && Displays 0.000000000000
WAIT
RETURN
* END OF PROC TESTDIVISIONOPERATOR.
We think STR(4/10000000,16,12) will display 0.000000400000, but:
?STR(4/10000000,16,12) && Displays 0.000000000000
2. CAUSE:
When VFP 9.0 and earlier versions calculate 4/10000000,
it will set the precision of the result float number:
n=3, eps = 0.5*10^(-(n+3)) = 5e-07
4/10000000 = 4e-07 < 5e-07,
So 4/10000000 = 0.
When VFP Advanced calculates 4/10000000,
it will adjust the precision of the result float number to 15 valid digits:
n=15, eps = 0.5*10^(-(n+3)) = 5e-18
So 4/10000000 = 4e-07 = 0.000000400000.
3. RESOLUTION:
We can write some code to fix the BUG.
Fun4680c6 :: ; proc near
sub esp , 08h ;0x004680c6 : 83ec08
push ebx ;0x004680c9 : 53
push ebp ;0x004680ca : 55
push esi ;0x004680cb : 56
mov esi , eax ;0x004680cc : 8bf0
cmp byte ptr [ edi + 16 ] , 0FAh ;0x004680ce : 807f10fa
mov dword ptr [ esp + 16 ] , esi ;0x004680d2 : 89742410
je Label5ca396 ;0x004680d6 : 0f84ba221600
mov ecx , dword ptr [edi] ;0x004680dc : 8b0f
test ecx , ecx ;0x004680de : 85c9
mov dword ptr [ esp + 12 ] , ecx ;0x004680e0 : 894c240c
jnl Label465adf ;0x004680e4 : 0f8df5d9ffff
Label4680ea ::
mov eax , ecx ;0x004680ea : 8bc1
cdq ;0x004680ec : 99
xor eax , edx ;0x004680ed : 33c2
sub eax , edx ;0x004680ef : 2bc2
cmp eax , 07FFFFFFFh ;0x004680f1 : 3dffffff7f
jg Label5ca416 ;0x004680f6 : 0f8f1a231600
cmp ecx , 080000000h ;0x004680fc : 81f900000080
je Label5ca416 ;0x00468102 : 0f840e231600
cmp eax , 07FFFh ;0x00468108 : 3dff7f0000
jg Label5ca3f8 ;0x0046810d : 0f8fe5221600
mov byte ptr [esi] , 0F9h ;0x00468113 : c606f9
mov al , byte ptr [ edi + 17 ] ;0x00468116 : 8a4711
inc esi ;0x00468119 : 46
mov byte ptr [esi] , al ;0x0046811a : 8806
inc esi ;0x0046811c : 46
mov word ptr [esi] , cx ;0x0046811d : 66890e
mov ecx , dword ptr [ esp + 16 ] ;0x00468120 : 8b4c2410
add esi , 02h ;0x00468124 : 83c602
mov eax , esi ;0x00468127 : 8bc6
pop esi ;0x00468129 : 5e
pop ebp ;0x0046812a : 5d
sub eax , ecx ;0x0046812b : 2bc1
pop ebx ;0x0046812d : 5b
add esp , 08h ;0x0046812e : 83c408
ret ;0x00468131 : c3
Label5ca396 ::
movzx eax ,byte ptr [ edi + 18 ] ;0x005ca396 : 0fb64712
add eax , 03h ;0x005ca39a : 83c003
;
; ----------------------------------------------------------------------------------------------------
; VFP 9.0 FIX - ADJUST THE PRECISION OF THE FLOATING-POINT NUMBERS FOR THE DIVISION OPERATOR
; August 2020
; ----------------------------------------------------------------------------------------------------
; CCB
;
; Adjust the precision of the floating-point numbers for the division operator.
;
; 2020/8/29, by ccb
;
cmp dword ptr vfpa_sys9035_data,00h
je Label5ca39d
cmp dword ptr [ esp + 14h ] , offset Label847742 ;; Fun8474bb .. ; proc near
jne Label5ca39d
cmp byte ptr [ edi + 17 ] , 0Fh
jae Label5ca39d
movzx ecx ,byte ptr [ edi + 17 ]
add eax , 0Fh
sub eax , ecx
Label5ca39d ::
cmp eax , 012h ;0x005ca39d : 83f812
mov ebp , eax ;0x005ca3a0 : 8be8
jl Label5ca3a9 ;0x005ca3a2 : 7c05
mov ebp , 012h ;0x005ca3a4 : bd12000000
Label5ca3a9 ::
fld qword ptr [ edi + 8 ] ;0x005ca3a9 : dd4708
lea ebx , dword ptr [ edi + 8 ] ;0x005ca3ac : 8d5f08
sub esp , 08h ;0x005ca3af : 83ec08
fstp qword ptr [ esp ] ;0x005ca3b2 : dd1c24
call _isnan ;0x005ca3b5 : ff150c799100
add esp , 08h ;0x005ca3bb : 83c408
test eax , eax ;0x005ca3be : 85c0
jne Label5ca3d4 ;0x005ca3c0 : 7512
fld qword ptr [ebx] ;0x005ca3c2 : dd03
fabs ;0x005ca3c4 : d9e1
fcomp qword ptr [ 8 * ebp + offset Data922450 ] ;0x005ca3c6 : dc1ced50249200
fstsw ax ;0x005ca3cd : dfe0
test byte ptr ah , 041h ;0x005ca3cf : f6c441
jp Label5ca423 ;0x005ca3d2 : 7a4f
Label5ca3d4 ::
fld qword ptr [ Data91fbc8 ] ;0x005ca3d4 : dd05c8fb9100
jmp Label5ca421 ;0x005ca3da : eb45
Label5ca3dc ::
mov byte ptr [esi] , 0F8h ;0x005ca3dc : c606f8
mov al , byte ptr [ edi + 17 ] ;0x005ca3df : 8a4711
inc esi ;0x005ca3e2 : 46
mov byte ptr [esi] , al ;0x005ca3e3 : 8806
inc esi ;0x005ca3e5 : 46
mov byte ptr [esi] , cl ;0x005ca3e6 : 880e
mov ecx , dword ptr [ esp + 16 ] ;0x005ca3e8 : 8b4c2410
inc esi ;0x005ca3ec : 46
mov eax , esi ;0x005ca3ed : 8bc6
pop esi ;0x005ca3ef : 5e
pop ebp ;0x005ca3f0 : 5d
sub eax , ecx ;0x005ca3f1 : 2bc1
pop ebx ;0x005ca3f3 : 5b
add esp , 08h ;0x005ca3f4 : 83c408
ret ;0x005ca3f7 : c3
Label5ca3f8 ::
mov byte ptr [esi] , 0E9h ;0x005ca3f8 : c606e9
mov dl , byte ptr [ edi + 17 ] ;0x005ca3fb : 8a5711
inc esi ;0x005ca3fe : 46
mov byte ptr [esi] , dl ;0x005ca3ff : 8816
inc esi ;0x005ca401 : 46
mov dword ptr [esi] , ecx ;0x005ca402 : 890e
mov ecx , dword ptr [ esp + 16 ] ;0x005ca404 : 8b4c2410
add esi , 04h ;0x005ca408 : 83c604
mov eax , esi ;0x005ca40b : 8bc6
pop esi ;0x005ca40d : 5e
pop ebp ;0x005ca40e : 5d
sub eax , ecx ;0x005ca40f : 2bc1
pop ebx ;0x005ca411 : 5b
add esp , 08h ;0x005ca412 : 83c408
ret ;0x005ca415 : c3
Label5ca416 ::
fild dword ptr [ esp + 12 ] ;0x005ca416 : db44240c
lea ebx , dword ptr [ edi + 8 ] ;0x005ca41a : 8d5f08
mov byte ptr [ edi + 18 ] , 00h ;0x005ca41d : c6471200
Label5ca421 ::
fstp qword ptr [ebx] ;0x005ca421 : dd1b
Label5ca423 ::
mov byte ptr [esi] , 0FAh ;0x005ca423 : c606fa
mov cl , byte ptr [ edi + 17 ] ;0x005ca426 : 8a4f11
mov byte ptr [ esi + 1 ] , cl ;0x005ca429 : 884e01
mov dl , byte ptr [ edi + 18 ] ;0x005ca42c : 8a5712
inc esi ;0x005ca42f : 46
inc esi ;0x005ca430 : 46
mov byte ptr [esi] , dl ;0x005ca431 : 8816
inc esi ;0x005ca433 : 46
pushd 08h ;0x005ca434 : 6a08
mov edx , ebx ;0x005ca436 : 8bd3
mov ecx , esi ;0x005ca438 : 8bce
call Fun42c19b ;0x005ca43a : e85c1de6ff
mov ecx , dword ptr [ esp + 16 ] ;0x005ca43f : 8b4c2410
add esi , 08h ;0x005ca443 : 83c608
mov byte ptr [esi] , 0CCh ;0x005ca446 : c606cc
inc esi ;0x005ca449 : 46
mov eax , esi ;0x005ca44a : 8bc6
pop esi ;0x005ca44c : 5e
pop ebp ;0x005ca44d : 5d
sub eax , ecx ;0x005ca44e : 2bc1
pop ebx ;0x005ca450 : 5b
add esp , 08h ;0x005ca451 : 83c408
ret ;0x005ca454 : c3
4. APPLIES TO:
VFP 6.0.8167.0
VFP 6.0.8961.0 (SP5)
VFP 7.0.0.9262
VFP 7.0.0.9465 (SP1)
VFP 8.0.0.2521
VFP 8.0.0.3117 (SP1)
VFP 9.0.0.2412
VFP 9.0.0.3504 (SP1)
VFP 9.0.0.4611 (SP2)
VFP 9.0.0.5015 (SP2)
VFP 9.0.0.5411 (SP2)
VFP 9.0.0.5721 (SP2)
VFP 9.0.0.5815 (SP2)
VFP 9.0.0.6303 (SP2)
VFP 9.0.0.6602 (SP2)
VFP 9.0.0.7423 (SP2)
The bug has been fixed in VFP Advanced.
5. REFERENCE WEBSITES:
1, baiyujia.com:
http://www.baiyujia.com
http://www.baiyujia.com/vfpdocuments/f_vfp9fix123.asp
http://www.baiyujia.com/vfpdocuments/f_vfp9fix23.asp
http://www.baiyujia.com/vfpdocuments/f_vfp9fix24.asp
http://www.baiyujia.com/vfpdocuments/f_vfp9fix97.asp
http://www.baiyujia.com/vfpdocuments/f_vfp9fix98.asp
http://www.baiyujia.com/vfpdocuments/f_vfp9fix255.asp
http://www.baiyujia.com/vfpdocuments/f_vfp9fix256.asp
http://www.baiyujia.com/vfpdocuments/f_vfp9fix257.asp
http://www.baiyujia.com/vfpdocuments/f_vfp9fix258.asp
http://www.baiyujia.com/vfpdocuments/f_vfp9fix259.asp
http://www.baiyujia.com/vfpdocuments/f_vfp9fix260.asp
http://www.baiyujia.com/vfpdocuments/f_vfp9fix303.asp
http://www.baiyujia.com/vfpdocuments/f_vfp9fix304.asp
http://www.baiyujia.com/vfpdocuments/f_vfp9fix305.asp
http://www.baiyujia.com/vfpdocuments/f_vfp9fix306.asp
2, mzvfp.com:
http://www.mzvfp.com/read.php?tid=106670
6. OTHER:
For reference only, there is no guarantees.
Any questions or suggestions, please send me an email at ccb2000@163.com.
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