On Thu, Oct 12, 2017 at 9:40 PM, Andrew Pinski <pins...@gmail.com> > -Wno-unkown-warning has already been handled silently since 4.6.0 > (which was released March 25, 2011): > https://gcc.gnu.org/onlinedocs/gcc-4.6.0/gcc/Warning-Options.html > > When an unrecognized warning option is requested (e.g., > -Wunknown-warning), GCC emits a diagnostic stating that the option is > not recognized. However, if the -Wno- form is used, the behavior is > slightly different: no diagnostic is produced for -Wno-unknown-warning > unless other diagnostics are being produced. This allows the use of > new -Wno- options with old compilers, but if something goes wrong, the > compiler warns that an unrecognized option is present. >
True, writing -Wno-some-future-version-warning-option is silently ignored. But -Wsome-future-version-warning-option currently generates a diagnostic message. The proposal is to have an explicit `-Wno-unknown-warnings` flag to suppress this diagnostic message. The documentation uses `-Wno-unknown-warning` as an example name (instead of saying something unwieldy like `-Wno-some-future-version-warning-option`). There's no actual `-Wno-unknown-warning` option. Here is a concrete example to make this less abstract: Suppose one wants to use `-Wsuggest-final-methods`. That's nice but versions 4.* of g++ do not support this flag; the build tool needs to avoid specifying this command line option if a 4.* g++ version is used. The problem isn't specifically about this flag and version; this is just an example; there are plenty of new useful warnings added in the recent past, such as (partial list): `-Wnonnull-compare`, `-Wnull-dereference`, `-Walloc-zero`, `-Wduplicated-cond`, `-Wrestrict`, ... Thanks, Oren.
