1. peek and poke under Windows XP
Has anyone had trouble with peek and poke when running EXW.EXE under
Windows XP? I have a simple program which runs fine under EX.EXE but
has a fatal error under EXW.EXE. From EXW.EXE it runs fine with trace
and trace(1), but not with trace(0).
This may have been discussed before, but suddenly I can't get the
Tropican search to find anything in our list.....
Thanks!
2. Re: peek and poke under Windows XP
From: "George Orr" <georgeorr at donet.com>
> Has anyone had trouble with peek and poke when running EXW.EXE under
> Windows XP? I have a simple program which runs fine under EX.EXE but
> has a fatal error under EXW.EXE. From EXW.EXE it runs fine with trace
> and trace(1), but not with trace(0).
>
> This may have been discussed before, but suddenly I can't get the
> Tropican search to find anything in our list.....
Could you provide us the program? I guess the program has a little bug
(it could be a one byte array overflow) which doesn't come out with DOS, but
is caught by XP.
Martin
3. Re: peek and poke under Windows XP
- Posted by euman at bellsouth.net
Mar 29, 2002
----- Original Message -----
From: "George Orr" <georgeorr at donet.com>
Subject: RE: peek and poke under Windows XP
> I am trying to create functions to rapidly put and get strings from
> memory using allocate_string() and peek. The basic functions are
>
> constant maxlength = 22 -- maximum length of word in dictionary
Oh yeah, I see now. if a string is shorter than 22 then you'll be trying to
peek( ) locations that are possibly protected by the system.
You will need to only peek( ) the strings length + 1.
Have you already done this?
personally, I think this is your problem
Euman
>
> function put_word(sequence word)
> atom aword
> aword = allocate_string(word)
> return aword
> end function
>
> function get_word(atom a)
> sequence w
> integer i
> w = peek({a,maxlength})
> i = 1
> while w[i]>0 do i += 1 end while
> return w[1..i-1]
> end function
4. Re: peek and poke under Windows XP
George Orr <georgeorr at donet.com> writes:
> I am trying to create functions to rapidly put and get strings from
> memory using allocate_string() and peek. The basic functions are
>
> constant maxlength = 22 -- maximum length of word in dictionary
>
> function put_word(sequence word)
> atom aword
> aword = allocate_string(word)
> return aword
> end function
>
> function get_word(atom a)
> sequence w
> integer i
> w = peek({a,maxlength})
> i = 1
> while w[i]>0 do i += 1 end while
> return w[1..i-1]
> end function
>
> The above functions work in Windows XP using ex.exe or exw.exe with
> trace turned on. Using under exw.exe without trace gives system errors.
> As you suggested, this seems to be an XP Virtual Machine issue. The
> peek({a,maxlength}) accesses memory that has not been allocated. Using
> ex.exe or exw.exe with trace on, this returns junk in the later bytes of
> the string, but the original string can be recovered by searching for
> the first 0 byte. Apparently the XP virutal machine objects to
> accessing memory that has not been allocated. When I modify the
> put_word function to pad the string to length maxlength, everything
> works in exw.exe.
>
> blankstr = repeat(0,maxlength)
> function put_word(sequence word)
> atom aword
> sequence bword
> bword = blankstr
> for i = 1 to length(word) do
> bword[i] = word[i]
> end for
> aword = allocate_string(bword)
> return aword
> end function
>
> There may be other problems with my coding, but it looks like the XP
> Virtual Machine may just be too smart for me!
No more the DOS days when you could do everything with the machine... 
> Thanks for your help. Please let me know if you see anything else that
> may be causing this.
The other way to fix is to replace get_word():
function get_word(atom a)
integer i,char
sequence s
i = 0
s = ""
while 1 do
char = peek(a+i)
if char = 0 then
-- end of string
exit
else
s &= char
i += 1
end if
end while
return s
end function
-- Martin
