Re: [Valgrind-users] uninitialised value in boolean expression

[Tom H. <to...@co...>]

In message <92A...@st...>
        Bill Torpey <Bil...@ny...> wrote:

> It appears that valgrind does not detect uninitialised values in boolean
> expressions.  I recently came across a problem with code similar to:
>
> int x;	// uninit
> bool y = (x == 0);	// uninit value not flagged
>
> The value of "y" was correctly flagged as uninitialised at assignment
> time and its use detected later in the program, but the use of the
> uninitialised value of x was not.  I assume that the reason the original
> expression did not raise a warning is that the compiler generated code
> to compute the boolean expression that did not use a condititional jump.
> Does this sound right?  Are there other similar constructs that valgrind
> is unable to flag, or does it depend on the code generated by the
> compiler?  Any workarounds?

The point is that you haven't yet used an uninitialised value in a way
that will affect the execution of your program.

Valgrind will only complain when (a) you make a conditional jump based
on uninitialised data or (b) you try and dereference an uninitialised
pointer.

So when you try and use x (or y) in such a way you will get told about
it, but not just because you assigned an uninitialised value to a
variable.

Tom 

-- 
Tom Hughes (to...@co...)
http://www.compton.nu/