Buildworld problem, warning: 'yy_flex_realloc' defined but not used

I have following problem when building world.

cc -O -pipe  -I/usr/src/lib/libc/include -I/usr/src/lib/libc/../../include 
-I/usr/src/lib/libc/i386 -D__DBINTERFACE_PRIVATE 
-I/usr/src/lib/libc/../../contrib/gdtoa -DINET6 -I/usr/obj/usr/src/lib/libc 
-DPOSIX_MISTAKE -I/usr/src/lib/libc/locale -DBROKEN_DES -DPORTMAP 
-DDES_BUILTIN -I/usr/src/lib/libc/rpc -DYP -DHESIOD -Wsystem-headers 
-Werror -Wall -Wno-format-y2k -Wno-uninitialized -c nslexer.c
/dev/stdout: In function `_nsyylex':
/dev/stdout:711: warning: label `find_rule' defined but not used
/usr/src/lib/libc/net/nslexer.l: At top level:
/dev/stdout:1678: warning: 'yy_flex_realloc' defined but not used
*** Error code 1

Stop in /usr/src/lib/libc.
*** Error code 1

Stop in /usr/src/lib.
*** Error code 1

Stop in /usr/src.
*** Error code 1

Stop in /usr/src.
*** Error code 1

Stop in /usr/src.
*** Error code 1

Stop in /usr/src.