[LLVMdev] Build Failure

[dag at cray.com]

Krzysztof Parzyszek <kparzysz at codeaurora.org> writes:

>> I'm curious about this statement.  Can you give an example?  I've
>> committed fixes to lots of -Wuninitialized warnings in my tree.  It's
>> all just initializing local variables, which shouldn't result in extra
>> stores.
>
> The logic of the program may be such that the actual store (not the
> "pre-initialization") always happens before any uses, but the compiler
> may be unable to prove it.  In such case, the added initialization
> will extend the live range of the object and may result in a register
> spill.

If that's really the case, then the variable is declared much too early
and the declaration should be moved.

> I believe that in the vast majority of cases this is not going to be a
> problem, and the warning is shown because of the basic nature of the
> front-end's analysis.

It's a problem if we keep ignoring warnings and we miss real bugs
because there are so many warning messages that things get lost.

I have fixed several dozen warnings now.

                           -David