../common/regex.c: In function '__advance':
../common/regex.c:175:3: error: this statement may fall through [-Werror=implicit-fallthrough=]
   (void) __xpop(0);
   ^~~~~~~~~~~~~~~~
../common/regex.c:176:2: note: here
  case EGRP|PLUS:
  ^~~~
../common/regex.c:277:6: error: this statement may fall through [-Werror=implicit-fallthrough=]
   if (*lp++ == '\0')
      ^
../common/regex.c:279:2: note: here
  case CDOT|STAR:
  ^~~~
../common/regex.c:285:6: error: this statement may fall through [-Werror=implicit-fallthrough=]
   if (*lp++ != *ep)
      ^
../common/regex.c:287:2: note: here
  case CCHR|STAR:
  ^~~~
../common/regex.c:297:6: error: this statement may fall through [-Werror=implicit-fallthrough=]
   if (!(lp = (char *)__advance(lp, ep+1)))
      ^
../common/regex.c:299:2: note: here
  case SGRP|A768:
  ^~~~
../common/regex.c:315:6: error: this statement may fall through [-Werror=implicit-fallthrough=]
   if (!__cclass(ep, *lp++, ep[-1] == (CCL | PLUS)))
      ^
../common/regex.c:317:2: note: here
  case CCL|STAR:
  ^~~~
cc1: all warnings being treated as errors