[ritt@pc5082 /tmp]$ tar -xzvf elog-2.5.9-2.tar.gz
elog-2.5.9/
elog-2.5.9/doc/
elog-2.5.9/doc/adminguide.html
...
mxml/
mxml/mxml.c
mxml/strlcpy.c
mxml/mxml.h
mxml/strlcpy.h
[ritt@pc5082 /tmp]$ cd elog-2.5.9
[ritt@pc5082 elog-2.5.9]$ make
gcc -O3 -funroll-loops -fomit-frame-pointer -W -Wall -o elog src/elog.c
gcc -O3 -funroll-loops -fomit-frame-pointer -W -Wall -c -o regex.o src/regex.c
... skipping warnings ...
gcc -O3 -funroll-loops -fomit-frame-pointer -W -Wall -c -o mxml.o ../mxml/mxml.c
gcc -O3 -funroll-loops -fomit-frame-pointer -W -Wall -c -o strlcpy.o ../mxml/strlcpy.c
gcc -O3 -funroll-loops -fomit-frame-pointer -W -Wall -I../mxml -o elogd src/elogd.c regex.o
mxml.o strlcpy.o
gcc -O3 -funroll-loops -fomit-frame-pointer -W -Wall -o elconv src/elconv.c
[ritt@pc5082 elog-2.5.9]$

--------------
No undefined functions here. I guess you have an old Makefile? Just use the complete tar
package from the last version.