On Sat, Sep 12, 2015 at 12:29:05AM +0200, Bernd Schmidt wrote: > On 09/12/2015 12:12 AM, Mark Wielaard wrote: > >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 with -Wunused-variable. And it adds > >a new option -Wno-unused-const-variable to turn this warning off. New > >testcases are included to test the new warning with -Wunused-variable > >and suppressing it with -Wno-unused-const-variable or unused attribute. > > > PR c/28901 > > * 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. > > Should these go into c-c++-common?
No. It is C only. But I realize that isn't really clear from my patch nor from the documentation I wrote for it. Since in C++ a const isn't by default file scoped and const variables always need to be initialized they are used differently than in C. Where in C you would use a #define in C++ you would use a const. So the cxx_warn_unused_global_decl () lang hook explicitly says to not warn about them. Although I think that is correct, I now think it is confusing you cannot enable the warning for C++ if you really want to. It should be off by default for C++, but on by default for C when -Wunused-variable is enabled. But it would actually be nice to be able to use it too for C++ if the user really wants to instead of having the warning suppression for C++ hardcoded. > Otherwise I'm ok with the patch, please > wait a few days to see if there are objections to this change then commit. I'll rewrite my patch a little, add some C++ testcases, and update the documentation. Then we can discuss again. Thanks, Mark
