[Bug c/57258] New: unused variable warning is emitted for volatile variables

["nszabolcs at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57258

            Bug ID: 57258
           Summary: unused variable warning is emitted for volatile
                    variables
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nszabolcs at gmail dot com

unused variable warnings are incorrectly issued for
volatile variables

a volatile variable is only unused if it is not
accessed, otherwise code will be generated for
using it following the semantics of the abstract
machine

in the following example the compiler gives a
warning eventhough the generated code uses x:

$ cat example.c
void f()
{
        volatile int x = 0;
}

$ gcc-4.8 -c -Wunused-variable example.c
example.c: In function 'f':
example.c:3:15: warning: unused variable 'x' [-Wunused-variable]
  volatile int x = 0;
               ^