KERNCONF

[...]
options       IPSEC_DEBUG             # debug for IP security
[...]

fails because of: -Wimplicit-function-declaration

cc -target x86_64-unknown-freebsd13.2 --sysroot=/usr/obj/usr/src/amd64.amd64/tmp -B/usr/obj/usr/src/amd64.amd64/tmp/usr/bin -c -O2
-pipe  -fno-strict-aliasing  -g -nostdinc  -I. -I/usr/src/sys -I/usr/src/sys/contrib/ck/include -I/usr/src/sys/contrib/libfdt -D_KE
RNEL -DHAVE_KERNEL_OPTION_HEADERS -include opt_global.h -fno-common    -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -MD  -M
F.depend.key_debug.o -MTkey_debug.o -fdebug-prefix-map=./machine=/usr/src/sys/amd64/include -fdebug-prefix-map=./x86=/usr/src/sys/x
86/include -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float  -fno-asynchronous-unwind-tables -ffreestanding -fwrapv -fs
tack-protector -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wcast-qual -Wunde
f -Wno-pointer-sign -D__printf__=__freebsd_kprintf__ -Wmissing-include-dirs -fdiagnostics-show-option -Wno-unknown-pragmas -Wno-err
or=tautological-compare -Wno-error=empty-body -Wno-error=parentheses-equality -Wno-error=unused-function -Wno-error=pointer-sign -W
no-error=shift-negative-value -Wno-address-of-packed-member -Wno-error=unused-but-set-variable -Wno-format-zero-length   -mno-aes -
mno-avx  -std=iso9899:1999 -Werror  /usr/src/sys/netipsec/key_debug.c
/usr/src/sys/netipsec/key_debug.c:885:7: error: implicit declaration of function 'SECASVAR_LOCK' is invalid in C99 [-Werror,-Wimpli
cit-function-declaration]
                   SECASVAR_LOCK(sav);
                   ^
/usr/src/sys/netipsec/key_debug.c:887:7: error: implicit declaration of function 'SECASVAR_UNLOCK' is invalid in C99 [-Werror,-Wimp
licit-function-declaration]
                   SECASVAR_UNLOCK(sav));
                   ^
/usr/src/sys/netipsec/key_debug.c:887:7: note: did you mean 'SECASVAR_LOCK'?
/usr/src/sys/netipsec/key_debug.c:885:7: note: 'SECASVAR_LOCK' declared here
                   SECASVAR_LOCK(sav);
                   ^
/usr/src/sys/netipsec/key_debug.h:61:6: note: expanded from macro 'KEYDBG'
           arg;                \
           ^
2 errors generated.