C: Undefined reference to LibConfuse internal functions - c

Question

I am testing LibConfuse on Code::Blocks trying to build the simplest first example on the tutorial:
#include <stdio.h>
#include <confuse.h>
int main(void)
{
cfg_opt_t opts[] =
{
CFG_STR("target", "World", CFGF_NONE),
CFG_END()
};
cfg_t *cfg;
cfg = cfg_init(opts, CFGF_NONE);
if(cfg_parse(cfg, "hello.conf") == CFG_PARSE_ERROR)
return 1;
printf("Hello, %s!\n", cfg_getstr(cfg, "target"));
cfg_free(cfg);
return 0;
}
But I get the below errors when compiling:
Undefined reference to "cfg_init".
Undefined reference to "cfg_parse".
Undefined reference to "cfg_getstr".
Undefined reference to "cfg_free".
Note that there are no errors about the #include <confuse.h> line nor about the constans, like CFGF_NONE.
I installed LibConfuse with:
# sudo apt-get update
# sudo apt-get install libconfuse*
What is going on here and how can I solve it?
Further Data:
Operating System: Ubuntu 16.04 .
Tested on two different PC computers.
Tested on RaspBerry Pi running RaspBian.
Code::Blocks version 17.12 .
Tested compiling on Clang with same results.
Another detail: I use to cross-compile to FreeBSD target, so I tested this basic program with my usual procedure to generate binaries for FreeBSD x64:
$ clang -target x86_64-unknown-freebsd10.0 --sysroot=/opt/cross-freebsd-10/ main.c
/tmp/main-0044e3.o: En la función `main':
main.c:(.text+0x96): referencia a `cfg_init' sin definir
main.c:(.text+0xb3): referencia a `cfg_parse' sin definir
main.c:(.text+0xde): referencia a `cfg_getstr' sin definir
main.c:(.text+0x104): referencia a `cfg_free' sin definir
clang: error: linker command failed with exit code 1 (use -v to see invocation)
As can be seen, results are the same.
More details about compilation (to x64 Linux) when using clang :
$ clang main.c -v clang version 3.8.0-2ubuntu4 (tags/RELEASE_380/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.0.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.0.0
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0
Candidate multilib: .;#m64
Selected multilib: .;#m64
"/usr/lib/llvm-3.8/bin/clang" -cc1 -triple x86_64-pc-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -main-file-name main.c -mrelocation-model static -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -v -dwarf-column-info -debugger-tuning=gdb -resource-dir /usr/lib/llvm-3.8/bin/../lib/clang/3.8.0 -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-3.8/bin/../lib/clang/3.8.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -fdebug-compilation-dir /media/Almacen01/Temporal/CPlusPlus/PruebaGeneral -ferror-limit 19 -fmessage-length 83 -fobjc-runtime=gcc -fdiagnostics-show-option -fcolor-diagnostics -o /tmp/main-06952f.o -x c main.c
clang -cc1 version 3.8.0 based upon LLVM 3.8.0 default target x86_64-pc-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/local/include
/usr/lib/llvm-3.8/bin/../lib/clang/3.8.0/include
/usr/include/x86_64-linux-gnu
/usr/include
End of search list.
"/usr/bin/ld" -z relro --hash-style=gnu --build-id --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o a.out /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../x86_64-linux-gnu/crt1.o /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../x86_64-linux-gnu/crti.o /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/crtbegin.o -L/usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0 -L/usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../x86_64-linux-gnu -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu -L/usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../.. -L/usr/lib/llvm-3.8/bin/../lib -L/lib -L/usr/lib /tmp/main-06952f.o -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/crtend.o /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../x86_64-linux-gnu/crtn.o
/tmp/main-06952f.o: En la función `main':
main.c:(.text+0x96): referencia a `cfg_init' sin definir
main.c:(.text+0xb3): referencia a `cfg_parse' sin definir
main.c:(.text+0xde): referencia a `cfg_getstr' sin definir
main.c:(.text+0x104): referencia a `cfg_free' sin definir
clang: error: linker command failed with exit code 1 (use -v to see invocation)
UPDATE:
I have tested LibConfig (as long as it is supposed to implement equivalent features) :
sudo apt-get install libconfig-dev
and, when trying to compile the included /examples/example1.c file, I get equivalent results: multiple undefined references on LibConfig functions.

Answer 1

You need to tell the linker where to find the libraries.
Check https://c-for-dummies.com/blog/?p=2159.