Adding google-test to a subfolder in a CMake project - cmake

Question

I have just added google-test source code to libs/gtest-1.6.4 directory in my project. There is a libs/gtest-1.6.4/CMakeLists.txt file. In the top-most CMakeLists.txt, I have added add_subdirectory('libs/gtest-1.6.4'). The structure of the project is
|- CMakeLists.txt
|- src
|- CMakeLists.txt
|- *.h and *.cc
|- libs
|- gtest-1.6.4
|- CMakeLists.txt
|- gtest source code etc.
|- other subdirectories
Now I add #include "gtest/gtest.h" in one of the header file. Compilation fails with
gtest/gtest.h: No such file or directory
compilation terminated.
Here is the snippet of my src/CMakeLists.txt file.
set( Boost_USE_STATIC_LIBS ON )
find_package( Boost COMPONENTS graph regex system filesystem thread REQUIRED)
.. Normal cmake stuff ...
INCLUDE_DIRECTORIES(${Boost_INCLUDE_DIRS} )
# This line is added for google-test
INCLUDE_DIRECTORIES(${GTEST_INCLUDE_DIRS} ${COMMON_INCLUDES})
add_executable(Partitioner
print_function.cc
methods.cc
partitioner.cc
main.cc
)
TARGET_LINK_LIBRARIES(Partitioner ${Boost_LIBRARIES})
TARGET_LINK_LIBRARIES(Partitioner ${GTEST_LIBRARIES})
What am I missing?

Answer 1

Looking at GTest's CMakeLists.txt, it looks like their include path is ${gtest_SOURCE_DIR}/include. They also define the library as a CMake target called gtest (this is wrapped in a macro cxx_library(gtest ...) currently on line 70).
So it looks like you need to do:
...
# This line is added for google-test
INCLUDE_DIRECTORIES(${GTEST_INCLUDE_DIRS} ${COMMON_INCLUDES})
INCLUDE_DIRECTORIES(${gtest_SOURCE_DIR}/include ${COMMON_INCLUDES})
...
TARGET_LINK_LIBRARIES(Partitioner ${Boost_LIBRARIES})
TARGET_LINK_LIBRARIES(Partitioner ${GTEST_LIBRARIES})
TARGET_LINK_LIBRARIES(Partitioner ${Boost_LIBRARIES} gtest)
You'd also have to ensure that in your root CMakeLists.txt, you've called add_subdirectory(libs/gtest-1.6.4) before add_subdirectory(src) so that the GTest variables are correctly set when they're being used in "src/CMakeLists.txt".

Answer 2

As mentioned in accepted answer,
I did put my GoogleTest stuff up before my add_subdirectory() lines and it worked.
# The ROOT CMakeLists.txt
enable_testing()
include(CTest)
# https://google.github.io/googletest/quickstart-cmake.html
include(FetchContent)
FetchContent_Declare(
googletest
URL https://github.com/google/googletest/archive/....zip
)
# For Windows: Prevent overriding the parent project's compiler/linker settings
set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
FetchContent_MakeAvailable(googletest)
include(GoogleTest)
add_subdirectory(some)
add_subdirectory(other)
add_subdirectory(another)
And in one of those sub directory, I see tests work.
# A CMakeLists.txt in a sub directory
#enable_testing() # NOT REQUIRED, hence, commented out
#include(CTest) # NOT REQUIRED, hence, commented out
#include(GoogleTest) # NOT REQUIRED, hence, commented out
add_executable(
mytest
test/mytest.cpp
)
target_link_libraries(
mytest
gtest_main
)
gtest_discover_tests(
mytest
)