This has been like this for not-quite a day:

cc -O2 -DALL_STATE  -Wall -Wstrict-prototypes -Wmissing-prototypes
-Wpointer-arith -Wno-uninitialized -Werror   -D_LIBC -DNLS -DYP -DHESIOD
-DLIBC_SCCS -DSYSLIBC_SCCS  -D_REENTRANT -I/usr/src/lib/libc/include
-DINET6 -D__DBINTERFACE_PRIVATE
-I/usr/src/lib/libc/../../libexec/ld.elf_so -I/usr/src/lib/libc/dlfcn
-DRESOLVSORT -I. -DPOSIX_MISTAKE -DPORTMAP -DFLOATING_POINT -c
/usr/src/lib/libc/locale/___runetype_mb.c
cc1: warnings being treated as errors
/usr/src/lib/libc/locale/___runetype_mb.c:49: warning: function
declaration isn't a prototype
*** Error code 1

Stop.