Hi, I compiled syslog-ng-3.25.1 using the following code: tar -xvzf syslog-ng_3.25.1.tar.gz mkdir -p syslog-ng_3.25.1/build cd syslog-ng_3.25.1/build ../configure --prefix=/home/nsaboo/Desktop/Cproject/syslog/syslog-ng_3.25.1/install make make install Post installation,the folder structure looks like this: nsaboo@ubuntu:~/Desktop/Cproject/syslog/syslog-ng-3.25.1/install$ ls -lrt total 28 drwxrwxr-x 2 nsaboo nsaboo 4096 Feb 11 04:08 sbin drwxrwxr-x 2 nsaboo nsaboo 4096 Feb 11 04:08 bin drwxr-xr-x 2 nsaboo nsaboo 4096 Feb 11 04:08 var drwxr-xr-x 3 nsaboo nsaboo 4096 Feb 11 04:08 share drwxrwxr-x 4 nsaboo nsaboo 4096 Feb 11 04:08 include drwxr-xr-x 3 nsaboo nsaboo 4096 Feb 11 04:08 etc drwxrwxr-x 4 nsaboo nsaboo 4096 Feb 18 00:35 lib nsaboo@ubuntu:~/Desktop/Cproject/syslog/syslog-ng-3.25.1/install$ I have a C code base (syslog-node.c) and header file (node.h) that is internally calling syslog-ng patterndb apis': I have a main.c file that calls methods in 'syslog-node.c'. My header file has following methods: typedef void (*key_value_cb)(const char* key, const char* value, size_t value_len, int data); int initialize_engine(const char* filename, const char* module_path, key_value_cb cb); int reload_pattern_db(const char* filename, key_value_cb cb); int load_pattern_db(const char* filename, key_value_cb cb); void match(const char* pattern, size_t pattern_len, const char* program, size_t program_len); int shutdown(); I am calling following gcc command to create a binary but it is erroring out: gcc -L/home/nsaboo/Desktop/Cproject/syslog/syslog-ng-3.25.1/install/lib lsyslog-ng -L/home/nsaboo/Desktop/Cproject/syslog/syslog-ng-3.25.1/install/lib/syslog-ng ldbparser -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -I/home/nsaboo/Desktop/Cproject/syslog/syslog-ng-3.25.1/install/include/syslog-ng -I/home/nsaboo/Desktop/Cproject/syslog/syslog-ng-3.25.1/install/include -I/home/nsaboo/Desktop/Cproject/syslog/syslog-ng-3.25.1/ -I/home/nsaboo/Desktop/Cproject/syslog/syslog-ng-3.25.1/build/ -I/usr/local/include/eventlog/ syslog-node.c main.c -o main Error ===== nsaboo@ubuntu:~/Desktop/Cproject$ gcc -L/home/nsaboo/Desktop/Cproject/syslog/syslog-ng-3.25.1/install/lib -lsyslog-ng -L/home/nsaboo/Desktop/Cproject/syslog/syslog-ng-3.25.1/install/lib/syslog-ng -ldbparser -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -I/home/nsaboo/Desktop/Cproject/syslog/syslog-ng-3.25.1/install/include/syslog-ng -I/home/nsaboo/Desktop/Cproject/syslog/syslog-ng-3.25.1/install/include -I/home/nsaboo/Desktop/Cproject/syslog/syslog-ng-3.25.1/ -I/home/nsaboo/Desktop/Cproject/syslog/syslog-ng-3.25.1/build/ -I/usr/local/include/eventlog/ syslog-node.c main.c -o main /tmp/ccam1ao5.o: In function `pdbtool_pdb_emit_accumulate': syslog-node.c:(.text+0x55): undefined reference to `logmsg_registry' syslog-node.c:(.text+0x73): undefined reference to `nv_table_foreach' /tmp/ccam1ao5.o: In function `match': syslog-node.c:(.text+0x93): undefined reference to `log_msg_new_empty' syslog-node.c:(.text+0xb0): undefined reference to `log_msg_set_value' syslog-node.c:(.text+0xc9): undefined reference to `log_msg_set_value' syslog-node.c:(.text+0xdf): undefined reference to `pattern_db_process' syslog-node.c:(.text+0xeb): undefined reference to `log_msg_unref' /tmp/ccam1ao5.o: In function `reload_pattern_db': syslog-node.c:(.text+0x1e2): undefined reference to `pattern_db_free' syslog-node.c:(.text+0x1e7): undefined reference to `pattern_db_new' syslog-node.c:(.text+0x20b): undefined reference to `pattern_db_reload_ruleset' syslog-node.c:(.text+0x225): undefined reference to `pattern_db_set_emit_func' /tmp/ccam1ao5.o: In function `load_pattern_db': syslog-node.c:(.text+0x257): undefined reference to `pattern_db_free' syslog-node.c:(.text+0x25c): undefined reference to `pattern_db_new' syslog-node.c:(.text+0x280): undefined reference to `pattern_db_reload_ruleset' syslog-node.c:(.text+0x29a): undefined reference to `pattern_db_set_emit_func' /tmp/ccam1ao5.o: In function `initialize_engine': syslog-node.c:(.text+0x2ba): undefined reference to `app_startup' syslog-node.c:(.text+0x2c4): undefined reference to `msg_init' syslog-node.c:(.text+0x2cb): undefined reference to `resolvedConfigurablePaths' syslog-node.c:(.text+0x2d0): undefined reference to `resolved_configurable_paths_init' syslog-node.c:(.text+0x2db): undefined reference to `resolvedConfigurablePaths' syslog-node.c:(.text+0x2e5): undefined reference to `cfg_new' syslog-node.c:(.text+0x2fb): undefined reference to `cfg_set_global_paths' syslog-node.c:(.text+0x311): undefined reference to `cfg_load_module' syslog-node.c:(.text+0x327): undefined reference to `cfg_load_module' syslog-node.c:(.text+0x32c): undefined reference to `pattern_db_global_init' syslog-node.c:(.text+0x347): undefined reference to `pattern_db_free' syslog-node.c:(.text+0x34c): undefined reference to `pattern_db_new' syslog-node.c:(.text+0x370): undefined reference to `pattern_db_reload_ruleset' syslog-node.c:(.text+0x38a): undefined reference to `pattern_db_set_emit_func' /tmp/ccam1ao5.o: In function `shutdown': syslog-node.c:(.text+0x39a): undefined reference to `app_shutdown' collect2: error: ld returned 1 exit status Those functions are available in the shared libraries.nm command output shows the same nsaboo@ubuntu:~/Desktop/Cproject$ nm syslog/syslog-ng-3.25.1/install/lib/syslog-ng/libdbparser.so | grep T | grep 'pattern_db_set_emit_func' 0000000000010d40 T pattern_db_set_emit_func nsaboo@ubuntu:~/Desktop/Cproject$ nm syslog/syslog-ng-3.25.1/install/lib/syslog-ng/libdbparser.so | grep T | grep 'pattern_db_new' 0000000000010ef0 T pattern_db_new nsaboo@ubuntu:~/Desktop/Cproject$ nm syslog/syslog-ng-3.25.1/install/lib/syslog-ng/libdbparser.so | grep T | grep 'pattern_db_reload_ruleset' 0000000000010cc0 T pattern_db_reload_ruleset nsaboo@ubuntu:~/Desktop/Cproject$ nm syslog/syslog-ng-3.25.1/install/lib/libsyslog-ng.so.0 | grep T | grep 'log_msg_set_value' 0000000000080df0 T log_msg_set_value 00000000000811d0 T __log_msg_set_value_by_name 0000000000081220 T log_msg_set_value_indirect nsaboo@ubuntu:~/Desktop/Cproject$ nm syslog/syslog-ng-3.25.1/install/lib/libsyslog-ng.so | grep T | grep 'msg_init' 0000000000051990 T msg_init nsaboo@ubuntu:~/Desktop/Cproject$ nm syslog/syslog-ng-3.25.1/install/lib/libsyslog-ng.so | grep T | grep 'cfg_new' 0000000000039200 T cfg_new 0000000000039360 T cfg_new_snippet 0000000000039390 T cfg_new_subordinate I understand this is the C linking error where I am including all the dynamic shared libraries and header files, but not able to figure out what is causing this issue. Can someone please help me to determine what am I missing here ? Thanks, Nitish