http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25137
--- Comment #23 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2012-05-29 09:22:05 UTC --- It is explained here http://gcc.gnu.org/onlinedocs/gccint/Option-properties.html#Option-properties A patch like the following should work (plus removing the special handling in c-opts.c) Index: c.opt =================================================================== --- c.opt (revision 187628) +++ c.opt (working copy) @@ -463,7 +463,7 @@ Warn about suspicious declarations of \"main\" Wmissing-braces -C ObjC C++ ObjC++ Var(warn_missing_braces) Warning +C ObjC C++ ObjC++ Var(warn_missing_braces) Warning LangEnabledBy(C ObjC, Wall) Warn about possibly missing braces around initializers There is also EnabledBy, which is unconditional. The plan is to convert sub-options to use this infrastructure. There is also some functionality missing: * An option enabled only if two options are combined. (-Wextra && -Wunused enable -Wunused-parameter). * An option enabled by some arbitrary condition. And some options are problematic because they currently have bugs: warn_format is 0 by default but the value of -Wformat in the gcc_opts structure is -1, thus calling warning(OPT_Wformat) without checking warn_format means enabled by default. Some tests expect such diagnostics to be enabled by default. :-(
