https://gcc.gnu.org/bugzilla/show_bug.cgi?id=28901
--- Comment #9 from Mark Wielaard <mark at gcc dot gnu.org> --- Author: mark Date: Mon Sep 14 09:49:47 2015 New Revision: 227742 URL: https://gcc.gnu.org/viewcvs?rev=227742&root=gcc&view=rev Log: PR28901 -Wunused-variable ignores unused const initialised variables in C 12 years ago it was decided that -Wunused-variable shouldn't warn about static const variables because some code used const static char rcsid[] strings which were never used but wanted in the code anyway. But as the bug points out this hides some real bugs. These days the usage of rcsids is not very popular anymore. So this patch changes the default to warn about unused static const variables in C with -Wunused-variable. And it adds a new option -Wno-unused-const-variable to turn this warning off. For C++ this new warning is off by default, since const variables can be used as #defines in C++. New testcases for the new defaults in C and C++ are included testing the new warning and suppressing it with an unused attribute or using -Wno-unused-const-variable. gcc/ChangeLog PR c/28901 * toplev.c (check_global_declaration): Check and use warn_unused_const_variable. * doc/invoke.texi (Warning Options): Add -Wunused-const-variable. (-Wunused-variable): Remove non-constant. For C implies -Wunused-const-variable. (-Wunused-const-variable): New. gcc/c-family/ChangeLog PR c/28901 * c.opt (Wunused-variable): Option from common.opt. (Wunused-const-variable): New option. gcc/cp/ChangeLog PR c/28901 * cp-objcp-common.c (cxx_warn_unused_global_decl): Remove hard-coded VAR_P TREE_READONLY override. gcc/testsuite/ChangeLog PR c/28901 * g++.dg/warn/unused-variable-1.C: New test. * g++.dg/warn/unused-variable-2.C: Likewise. * gcc.dg/unused-4.c: Adjust warning for static const. * gcc.dg/unused-variable-1.c: New test. * gcc.dg/unused-variable-2.c: Likewise. Added: trunk/gcc/testsuite/g++.dg/warn/unused-variable-1.C trunk/gcc/testsuite/g++.dg/warn/unused-variable-2.C trunk/gcc/testsuite/gcc.dg/unused-variable-1.c trunk/gcc/testsuite/gcc.dg/unused-variable-2.c Modified: trunk/gcc/ChangeLog trunk/gcc/c-family/ChangeLog trunk/gcc/c-family/c.opt trunk/gcc/cp/ChangeLog trunk/gcc/cp/cp-objcp-common.c trunk/gcc/doc/invoke.texi trunk/gcc/testsuite/ChangeLog trunk/gcc/testsuite/gcc.dg/unused-4.c trunk/gcc/toplev.c
