Microsoft VB Bug

from Curtis Johnstone <[email protected]>, Fri, 30 Jun 2000 15:11:49 -0400

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Since we are dissing Microsoft today and I am not getting much done at work,
I'll make one more contribution. This absolutely KILLS me. I discovered it
last week while debugging some VB code I wrote.

In VB there is a Boolean data type which is either TRUE (which evaluates to
an integer "-1") or FALSE (integer "0"). Coming from a C/C++ background, it
is not uncommon to do something like:
if (condition) then ....
where condition is an expression that is not a Boolean data type but which
is implicitly cast to one. For example, in C/C++ where the condition is an
integer expression, "0" evaluates to a boolean FALSE and anything > 0 is
TRUE. This is the situation I was programming with in VB and I wasn't sure
if it was treated the same so in the debug window I did a little test:
> if 16 (or any > 0 integer) then print "Hello"
VB printed "Hello"
> if 0 then print "Hello"
VB didn't print anything.

Works like C/C++ I thought, and off I went. Two weeks later a found a bug in
my bitmap parsing code that used the code I describe above. It turns out
that if the condition in the "if" statement is integer you have to use "-1"
for TRUE and "0" for FALSE -- nothing else!!! That would be fine (just
restrictive) but look what VB does when you have an integer > 0:

> Dim iTemp As Integer
> iTemp = 16
>
> if iTemp then print "Hello" -- VB prints "Hello"
>
> if NOT iTemp then print "Hello" -- VB also prints "Hello" !!!!!

This defies all logic (and not to mention caused a bug in my code).
Apparently there is no Boolean translation for integers > 0 and instead of
issuing an error or doing something sensible, that expression evaluates to
TRUE AND also to FALSE. Yikes! I can't believe that that exists in the 6th
edition of VB.

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Since we are dissing Microsoft today =
and I am not getting much done at work, I'll make one more =
contribution. This absolutely KILLS me. I discovered it last week while =
debugging some VB code I wrote.

In VB there is a Boolean data type =
which is either TRUE (which evaluates to an integer "-1") or =
FALSE (integer "0"). Coming from a C/C++ background, it is =
not uncommon to do something like:

        if (condition) then ....
 where condition is an expression that =
is not a Boolean data type but which is implicitly cast to one. For =
example, in C/C++ where the condition is an integer expression, =
"0" evaluates to a boolean FALSE and anything > 0 is TRUE. =
This is the situation I was programming with in VB and I wasn't sure if =
it was treated the same so in the debug window I did a little =
test:

    > if 16 (or any =
> 0 integer) then print "Hello"
 VB printed "Hello"
     > if 0 then =
print "Hello"
 VB didn't print anything.


Works like C/C++ I thought, and off I =
went. Two weeks later a found a bug in my bitmap parsing code that used =
the code I describe above. It turns out that if the condition in the =
"if" statement is integer you have to use "-1" for =
TRUE and "0" for FALSE --  nothing else!!!  That =
would be fine (just restrictive) but look what VB does when you have an =
integer > 0:

> Dim iTemp As Integer
 > iTemp =3D 16
 > 
 > if iTemp then print =
"Hello"    -- VB prints =
"Hello"
 > 
 > if NOT iTemp then print =
"Hello"  -- VB also prints "Hello" =
!!!!!


This defies all logic (and not to =
mention caused a bug in my code). Apparently there is no Boolean =
translation for integers > 0 and instead of issuing an error or =
doing something sensible, that expression evaluates to TRUE AND also to =
FALSE. Yikes!  I can't believe that that exists in the 6th edition =
of VB.

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