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[ENHANCED] VFP 9.0 FIX - SYS(9100) ENABLES OR DISABLES CATCHING THE MEMORY ACCESS VIOLATION EXCEPTION
January 2024
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CCB
1. THE SYS(9100) FUNCTION:
SYS(9100) - Enables or disables catching the memory access violation exception
Enables or disables catching the memory access violation exception.
SYS(9100 [, 0 | 1 | 2])
Parameters
0
Disables catching the memory access violation exception. 0 is the startup default for Visual FoxPro Advanced
Runtime and Visual FoxPro Advanced Multi-threaded Runtime.
1
Enables catching the memory access violation exception. 1 is the startup default for Visual FoxPro Advanced
Interactive Development Environment (IDE).
2
Enables catching the memory access violation exception without the exception dialog.
Return Value
Character
Remarks
If we enable catching the memory access violation exception in Visual FoxPro Advanced,
when Visual FoxPro causes the memory access violation exception (exception code 0xC0000005),
it will display the exception dialog box twice,
and then it will display a dialog box "Are you sure you want to exit Visual FoxPro?",
if we select "Yes", it will exit Visual FoxPro,
if we select "No", it will cause the error "There is not enough memory to complete this operation (Error 43)",
and then it will return to Visual FoxPro, now we can do some important work, and then exit Visual FoxPro.
If we disable catching the memory access violation exception in Visual FoxPro Advanced,
when Visual FoxPro causes the memory access violation exception (exception code 0xC0000005),
it will display the exception dialog box twice, and then exit Visual FoxPro,
it is the same as Visual FoxPro 9.0 and earlier versions.
2. CAUSE:
There are some BUGs in the following code.
3. RESOLUTION:
We can write some code to fix the BUG.
Fun529fca :: ; proc near
push ebp ;0x00529fca : 55
mov ebp , esp ;0x00529fcb : 8bec
pushd 0FFFFFFFFh ;0x00529fcd : 6aff
pushd offset Data922268 ;0x00529fcf : 6868229200
pushd offset Label9160f9 ;0x00529fd4 : 68f9609100
mov eax , dword ptr fs:[00h] ;0x00529fd9 : 64a100000000
push eax ;0x00529fdf : 50
mov dword ptr fs:[00h] , esp ;0x00529fe0 : 64892500000000
push ecx ;0x00529fe7 : 51
push ecx ;0x00529fe8 : 51
mov eax , 02FBCh ;0x00529fe9 : b8bc2f0000
call Fun42c118 ;0x00529fee : e82521f0ff
mov eax , dword ptr [ Data937090 ] ;0x00529ff3 : a190709300
mov dword ptr [ ebp - 28 ] , eax ;0x00529ff8 : 8945e4
push ebx ;0x00529ffb : 53
push esi ;0x00529ffc : 56
push edi ;0x00529ffd : 57
mov dword ptr [ ebp - 24 ] , esp ;0x00529ffe : 8965e8
xor edi , edi ;0x0052a001 : 33ff
mov dword ptr [ ebp + 0FFFFD114h ] , edi ;0x0052a003 : 89bd14d1ffff
push edi ;0x0052a009 : 57
pushd 02710h ;0x0052a00a : 6810270000
push edi ;0x0052a00f : 57
mov ebx , dword ptr [ ebp + 8 ] ;0x0052a010 : 8b5d08
mov eax , ebx ;0x0052a013 : 8bc3
call Fun529bc5 ;0x0052a015 : e8abfbffff
mov dword ptr [ ebp + 0FFFFD0E4h ] , eax ;0x0052a01a : 8985e4d0ffff
mov dword ptr [ ebp + 0FFFFD10Ch ] , edi ;0x0052a020 : 89bd0cd1ffff
lea ecx , dword ptr [ ebp + 0FFFFFDE0h ] ;0x0052a026 : 8d8de0fdffff
mov dword ptr [ ebp + 0FFFFD100h ] , ecx ;0x0052a02c : 898d00d1ffff
mov byte ptr [ ebp + 0FFFFFDE0h ] , 00h ;0x0052a032 : c685e0fdffff00
movsx eax , ax ;0x0052a039 : 0fbfc0
;
; ----------------------------------------------------------------------------------------------------
; VFP 9.0 FIX - SYS(9100) ENABLES OR DISABLES CATCHING THE MEMORY ACCESS VIOLATION EXCEPTION
; May 2022
; ----------------------------------------------------------------------------------------------------
; CCB
;
; SYS(9100) - Enables or disables catching the memory access violation exception (exception code 0xC0000005).
;
; 2022/5/13, by ccb
;
cmp eax,9100
je vfpa_sys9100_start
pushd 064h ;0x0052a03c : 6a64
pop esi ;0x0052a03e : 5e
cmp eax , esi ;0x0052a03f : 3bc6
jle Label52a0d0 ;0x0052a041 : 0f8e89100000
mov ecx , 07EAh ;0x0052a047 : b9ea070000
cmp eax , ecx ;0x0052a04c : 3bc1
jg Label52a164 ;0x0052a04e : 0f8f10010000
je Label609b33 ;0x0052a054 : 0f84d9fa0d00
mov ecx , 04F6h ;0x0052a05a : b9f6040000
cmp eax , ecx ;0x0052a05f : 3bc1
jle Label52b6e0 ;0x0052a061 : 0f8e79160000
mov ecx , 07DBh ;0x0052a067 : b9db070000
cmp eax , ecx ;0x0052a06c : 3bc1
jg Label51f355 ;0x0052a06e : 0f8fe152ffff
je Label609700 ;0x0052a074 : 0f8486f60d00
add ecx , 0FFFFFFF9h ;0x0052a07a : 83c1f9
cmp eax , ecx ;0x0052a07d : 3bc1
jg Label4a4938 ;0x0052a07f : 0f8fb3a8f7ff
je Label4f6b07 ;0x0052a085 : 0f847ccafcff
sub eax , 04F7h ;0x0052a08b : 2df7040000
je Label60951e ;0x0052a090 : 0f8488f40d00
dec eax ;0x0052a096 : 48
je Label60950f ;0x0052a097 : 0f8472f40d00
sub eax , 0E4h ;0x0052a09d : 2de4000000
je Label609492 ;0x0052a0a2 : 0f84eaf30d00
sub eax , 01F4h ;0x0052a0a8 : 2df4010000
jne Label462026 ;0x0052a0ad : 0f85737ff3ff
lea eax , dword ptr [ ebp + 0FFFFFDE0h ] ;0x0052a0b3 : 8d85e0fdffff
push eax ;0x0052a0b9 : 50
push dword ptr [ ebp + 12 ] ;0x0052a0ba : ff750c
mov edx , ebx ;0x0052a0bd : 8bd3
call Fun4dc923 ;0x0052a0bf : e85f28fbff
4. APPLIES TO:
VFP 10 (VFP Advanced)
5. REFERENCE WEBSITES:
1, baiyujia.com:
http://www.baiyujia.com
http://www.baiyujia.com/vfpdocuments/f_vfp9fix213.asp
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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