how to split 'header', 'src', 'test' dir in cmake?(and donot add cmakelist.txt in each dir) - cmake

Question

when building a project stucture like following:
LinearAlgebra
|---HEADER
|-----|---Linear.h
|---SRC
|-----|---Linear.cpp
|---TEST
|-----|---hello_test.cc
here is my CMakeList.txt:
cmake_minimum_required(VERSION 3.10)
project(LinearAlgebra )
set(CMAKE_CXX_STANDARD 11)
include(FetchContent)
FetchContent_Declare(
googletest
URL https://github.com/google/googletest/archive/609281088cfefc76f9d0ce82e1ff6c30cc3591e5.zip
)
# For Windows: Prevent overriding the parent project's compiler/linker settings
set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
FetchContent_MakeAvailable(googletest)
add_library(LA_HEADER INTERFACE header/Linear.h)
add_library(LA_SRC INTERFACE src/Linear.cpp)
target_include_directories(LA_HEADER INTERFACE "${PROJECT_SOURCE_DIR}/header" "${PROJECT_SOURCE_DIR}/src")
enable_testing()
add_executable(
hello_test
test/hello_test.cc
)
target_link_libraries(
hello_test
gtest_main
LA_HEADER
LA_SRC
)
include(GoogleTest)
gtest_discover_tests(hello_test)
it works fine with cmake -S . -B build, but when it comes to cmake --build build following error occured:
Undefined symbols for architecture x86_64:
"Linear::Linear()", referenced from:
HelloTest_BasicAssertions_Test::TestBody() in hello_test.cc.o
it seems something wrong with my cmake file that didn't tell Linear.h where Linear.cpp located. So how to fix it ?? thanks for your help...

Answer 1

seems i misunderstand add_library, change three lines and it works out:
cmake_minimum_required(VERSION 3.10)
project(LinearAlgebra )
include_directories(header) # include_directories instead of add_library for .h files
add_library(LA_LIB src/Linear.cpp) # use add_library for .cpp files only!!!
set(CMAKE_CXX_STANDARD 11)
include(FetchContent)
FetchContent_Declare(
googletest
URL https://github.com/google/googletest/archive/609281088cfefc76f9d0ce82e1ff6c30cc3591e5.zip
)
# For Windows: Prevent overriding the parent project's compiler/linker settings
set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
FetchContent_MakeAvailable(googletest)
enable_testing()
add_executable(
hello_test
test/hello_test.cc
)
target_link_libraries(
hello_test
gtest_main
LA_LIB # link LA_LIB only..
)
include(GoogleTest)
gtest_discover_tests(hello_test)
leave it here for anyone have the same requirements.