[C] Fix PR57258: unused variable warning is emitted for volatile variables

[Mike Stump]

On Nov 8, 2013, at 2:25 AM, Bin.Cheng <amker.cheng@gmail.com> wrote:
> Thanks for elaborating.  The warning message is actually for no-use of
> variable, and it has few things to do with whether it's accessed or
> not.

I disagree.  If you examine why the warning was put in, you realize it was put in so that lazy programmers can find dead things.  Why do they want to do that, to remove the dead things.  This construct is a dead thing.  If you disagree, you'd have to say why the warning was produced.