Is GNUCASH, in fact, unsafe....

[Mike or Penny Novack]

>Avast used to complain about ,,,,,,
>
Our virus checkers will either fail to detect some viruses or give us 
some false positives or both. This isn't because they aren't good enough 
but because it is IMPOSSIBLE to have a program that can check the code 
of any other program (a "universal checker") to determine the runtime 
behavior of that code and be 100% correct in doing that. The behavior in 
this case being "acts like a virus" but in the original statement of 
what is known as the fundamental theorem of computation it was "loops". 
You prove it in the same way.

Assume that there was such a universal checker. You can think of it as a 
function V(p) that returns 1 if p will act like a virus and 0 if p will 
not act like a virus. Then construct the simple program P
   If V(p) then halt
     else "act like a virus"

What is the result of trying to check P? In other words, what is the 
result of  V(P)

See? This supposedly always correct virus checker gets P wrong.  So it 
can't exist.

Michael

PS: While almost any Computer Science person knows this theorem (and who 
first proved it) do not feel bad because you didn't. In the large shop 
where I worked for three decades I bet less than 2% of my co-workers 
did. Information Technology people are not the same as Computer Science 
people and besides, most of us had undergraduate degrees unrelated to 
either. Mine was Physics.