Link properly a library using cmake - c++

Question

I try to learn how to use cmake, and so I created a little project but when I try to compile I get this error : /usr/bin/ld : CMakeFiles/test.dir/main.cpp.o : dans la fonction « main » : main.cpp:(.text+0x2d) : référence indéfinie vers « la::Matrice<int>::Matrice(unsigned int, unsigned int) »
.
├── build
│   ├── CMakeCache.txt
│   ├── CMakeFiles
│   ├── cmake_install.cmake
│   ├── LinearAlgebra
│   └── Makefile
├── CMakeLists.txt
├── LinearAlgebra
│   ├── CMakeLists.txt
│   ├── Matrice.cpp
│   └── Matrice.hpp
└── main.cpp
./CmakeLists.txt :
cmake_minimum_required(VERSION 3.10)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED true)
project(test_project)
add_subdirectory(LinearAlgebra)
add_executable(test main.cpp)
link_libraries(test linear_algebra)
LinearAlgebra/CMakeLists.txt :
cmake_minimum_required(VERSION 3.10)
project(linear_algebra)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
set(SOURCES
Matrice.cpp
)
set(HEADERS
Matrice.hpp
)
add_library(linear_algebra ${HEADERS} ${SOURCES})
Do someone know where the problem is ?

Answer 1

With link_libraries you define which libraries will be linked for targets that are defined after this command and within the current directory.
You probably meant to use target_link_libraries which defines libraries to link to the given target.
The documentation suggests to use this over link_libraries whenever possible. It is explicit and better scoped.
cmake_minimum_required(VERSION 3.10)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED true)
project(test_project)
add_subdirectory(LinearAlgebra)
add_executable(test main.cpp)
target_link_libraries(test linear_algebra)