Problem with compiling

[swen100]

Hi,

at compiling with
gcc -o lib_mysqludf_fPROJ4.so lib_mysqludf_fPROJ4.c -I /usr/include/mysql/
i get the following messages:

/usr/lib64/gcc/x86_64-suse-linux/4.8/../../../../lib64/crt1.o: In function_start':
/home/abuild/rpmbuild/BUILD/glibc-2.18/csu/../sysdeps/x86_64/start.S:118: undefined reference to main' /tmp/ccJYp3wF.o: In functionlib_mysqludf_fPROJ4_info':
lib_mysqludf_fPROJ4.c:(.text+0xd1): undefined reference to pj_get_release' /tmp/ccJYp3wF.o: In functionfPROJ4_transform':
lib_mysqludf_fPROJ4.c:(.text+0x42b): undefined reference to pj_init_plus' lib_mysqludf_fPROJ4.c:(.text+0x457): undefined reference topj_init_plus'
lib_mysqludf_fPROJ4.c:(.text+0x4b0): undefined reference to pj_transform' lib_mysqludf_fPROJ4.c:(.text+0x528): undefined reference topj_free'
lib_mysqludf_fPROJ4.c:(.text+0x534): undefined reference to pj_free' /tmp/ccJYp3wF.o: In functionfPROJ4_Geo2UTM':
lib_mysqludf_fPROJ4.c:(.text+0x804): undefined reference to pj_init_plus' lib_mysqludf_fPROJ4.c:(.text+0x83e): undefined reference topj_init_plus'
lib_mysqludf_fPROJ4.c:(.text+0x8a3): undefined reference to pj_transform' lib_mysqludf_fPROJ4.c:(.text+0x904): undefined reference topj_free'
lib_mysqludf_fPROJ4.c:(.text+0x910): undefined reference to pj_free' /tmp/ccJYp3wF.o: In functionfPROJ4_UTM2Geo':
lib_mysqludf_fPROJ4.c:(.text+0xbcf): undefined reference to pj_init_plus' lib_mysqludf_fPROJ4.c:(.text+0xbee): undefined reference topj_init_plus'
lib_mysqludf_fPROJ4.c:(.text+0xc53): undefined reference to pj_transform' lib_mysqludf_fPROJ4.c:(.text+0xcd0): undefined reference topj_free'
lib_mysqludf_fPROJ4.c:(.text+0xcdc): undefined reference to pj_free' collect2: error: ld returned 1 exit status

what i am doing wrong? LibProj-devel is installed.