Re: [PATCH, tree-ssa] Avoid -Wuninitialized warning in try_unroll_loop_completely()

[Jeff Law <law at redhat dot com>]

On 04/15/2013 08:35 PM, Chung-Ju Wu wrote:
> You are right.
> After doing survey on http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings
> and reading related discussion thread, I realized it is a
> complicated detection and this is a false positive case.
>
> I was using gcc-4.6.3, which is provided by Ubuntu 12.04,
> and the warning is displayed during the compilation process.
> As I tried to build another native gcc by myself with
> current main trunk and used it to compile tree-ssa-loop-ivcanon.c again,
> there is no such warning at all.
> (See attachment for my console output.)
>
> So I am wondering if my patch is still valuable since
> such false positive warning is already fixed on trunk.
Thanks for checking on this stuff.  My preference would be to not add 
the initialization unless we're currently seeing false positive warnings 
with the trunk.

Anytime we add a dummy initialization like this to avoid a false 
positive, we run the risk of missing real bugs later if the nearby code 
is changed in such a way as to expose an uninitialized use, which we'd 
like to catch, but can't if we're inserted a dummy initialization.

Jeff