Link properly a library using cmake

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

Withlink_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)