[SOLVED] correctly using fplll as c++ library

correctly using fplll as c++ library

I'm trying to use the bkz_reduction function of the fplll library in my c++ programm, however, I always get an "undefined reference to `fplll::bkz_reduction(fplll::ZZ_mat<__mpz_struct [1]>&, int, int, fplll::FloatType, int)'" error.

Setup: I downloaded and installed fplll as described in the git (https://github.com/fplll/fplll/tree/master) under the 'install from source' on my wsl2 Ubuntu 22.04.3 (host: Windows 11). It is now under /home/my_username/fplll. When running the test_bkz that is included in the git, there are no problems at all.

What I want: I have a file test_stuff.cpp that includes a call of the bkz_reduction function:

...
#include <cstring>
#include <cstdlib>
#include <fplll.h>


using namespace std;
using namespace fplll;


int main()
{
    ...
    ZZ_mat<mpz_t> fplll_mat;
    fplll_mat = //gets set to some other value;

    int status = 0;
    status = bkz_reduction(fplll_mat, 10, BKZ_DEFAULT, FT_DEFAULT, 0);

    return 0;
}

Additionally I have a Makefile with

CFLAGS = -Wall -Wextra -march=native -mtune=native -O3 -fomit-frame-pointer
CXX = g++
CXXFLAGS = $(CFLAGS) -std=c++0x

test_stuff: tests/test_stuff.cpp
    $(CXX) $(CXXFLAGS) tests/test_stuff.cpp -o tests/test_stuff -lmpfr -lgmp

Calling 'make test_stuff' yields the mentioned "undefined reference to `fplll::bkz_reduction(fplll::ZZ_mat<__mpz_struct [1]>&, int, int, fplll::FloatType, int)'" error.

I have double-checked the correct input parameters of the function and the required types match. My VSCode has no troubles finding the bkz_reduction function and has also no objections regarding the function call.

After reading different internet contents, I assume that I'm not linking the fplll library correctly to my test_stuff program, however, my knowledge of linking is very limited. I tried to understand the Makefile of the test_bkz in the official fplll-git repository, but it's unfortunately too complex for me as a beginner.

I would appreciate any help or suggestions what to try. Seeing a correctly functioning example would also be great, anything I found used the python version fpylll to get access to the fplll functions.

Solution

You don't seem to tell the linker to link with fplll at all. Luckily this library ships a pkg-config file so you can ask pkg-config for the flags:

test_stuff: tests/test_stuff.cpp
    $(CXX) $(CXXFLAGS) tests/test_stuff.cpp -o tests/test_stuff -lmpfr -lgmp `pkg-config --libs fplll`