[Bug c/28901] -Wunused-variable ignores unused const initialised variables

["mark at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=28901

--- Comment #32 from Mark Wielaard <mark at gcc dot gnu.org> ---
Author: mark
Date: Mon Feb 22 22:42:19 2016
New Revision: 233616

URL: https://gcc.gnu.org/viewcvs?rev=233616&root=gcc&view=rev
Log:
PR28901 Add two levels for -Wunused-const-variable.

There is some controversy about enabling -Wunused-const-variable for all
unused static const variables because some feel there are too many errors
exposed in header files. Create two levels for -Wunused-const-variable.
One level to only check for unused static const variables in the main
compilation file. Which is enabled by -Wunused-variable. And a second
level that also checks for unused static const variables in included
files. Which must be explicitly enabled.

gcc/ChangeLog

        PR c/28901
        * cgraphunit.c (check_global_declaration): Check level of
        warn_unused_const_variable and main_input_filename.
        * doc/invoke.texi (Warning Options): Add -Wunused-const-variable=.
        (-Wunused-variable): For C implies -Wunused-const-variable=1.
        (-Wunused-const-variable): Explain levels 1 and 2.

gcc/c-family/ChangeLog

        PR c/28901
        * c.opt (Wunused-const-variable): Turn into Alias for...
        (Wunused-const-variable=): New option.

gcc/testsuite/ChangeLog

        PR c/28901
        * gcc.dg/unused-variable-3.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/unused-variable-3.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/c-family/ChangeLog
    trunk/gcc/c-family/c.opt
    trunk/gcc/cgraphunit.c
    trunk/gcc/doc/invoke.texi
    trunk/gcc/testsuite/ChangeLog