I'm packaging recutils for openSUSE and rpmlint throws a few complaints about functions being declared implicitly.
I fixed most of them with the attached patch, but I'm not sure how to solve this one:

E: gnu-recutils implicit-fortify-decl rec-sex-tab.c:66

---
/bin/sh ../libtool  --tag=CC   --mode=compile gcc -DHAVE_CONFIG_H -I.  -I../lib -DLOCALEDIR=\"/usr/share/locale\"  -DUUID_TYPE   -fmessage-length=0 -grecord-gcc-switches -$
libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I../lib -DLOCALEDIR=\"/usr/share/locale\" -DUUID_TYPE -fmessage-length=0 -grecord-gcc-switches -O2 -Wall -D_FORTIFY_SOURCE=2 -f$
$ches -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -g -c -o rec-sex-tab.lo  rec-sex-tab.c
libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I../lib -DLOCALEDIR=\"/usr/share/locale\" -DUUID_TYPE -fmessage-length=0 -grecord-gcc-switches -O2 -Wall -D_FORTIFY_SOURCE=2 -f$
rec-sex-tab.c: In function 'sexparse':
rec-sex-tab.c:66:25: warning: implicit declaration of function 'sexlex'; did you mean 'strlen'? [-Wimplicit-function-declaration]
 #define yylex           sexlex
                         ^
---

(also see attached full log)