[util] Use HB_FALLTHROUGH Sure, gcc knows to warn about this as well: ../../util/options.cc:175:17: warning: this statement may fall through [-Wimplicit-fallthrough=] case 1: m.r = m.t; ~~~~^~~~~ ../../util/options.cc:176:5: note: here case 2: m.b = m.t; ^~~~ But HOLY SMOKES, look at clang -Weverything bot message: options.cc:176:5: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough] case 2: m.b = m.t; ^ options.cc:176:5: note: insert 'HB_FALLTHROUGH;' to silence this warning case 2: m.b = m.t; ^ HB_FALLTHROUGH; Right, it's telling me to insert "HB_FALLTHROUGH;" there!!!!!!!!!