[SOLVED] Linking against GTest fails

Issue

I have the following CMakeLists.txt:

cmake_minimum_required(VERSION 3.15)

set(CMAKE_CXX_STANDARD 17)

# adding library
set(ST_SRC simple_tree.cpp)
add_library(st ${ST_SRC})
target_include_directories(st PUBLIC ${PROJECT_SOURCE_DIR}/include/data_structures/simple_tree/)

# adding googletest
set(GOOGLETEST_PATH ~/local/googletest)
set(GTEST_INCLUDE_DIR ~/local/include/)
set(GTEST_LIBRARY ~/local/lib/)
set(GTEST_MAIN_LIBRARY ~/local/lib/)
find_package(GTest REQUIRED)

# adding tests
set(TEST_TARGET test_simple_tree)
add_executable(${TEST_TARGET} test_simple_tree.cpp)
target_include_directories(${TEST_TARGET}
                        PUBLIC
                        ${PROJECT_SOURCE_DIR}/include/data_structures/simple_tree
                        ${GOOGLETEST_PATH}
                        ${GTEST_INCLUDE_DIR})
target_link_libraries(${TEST_TARGET} PUBLIC st)
target_link_libraries(${TEST_TARGET} PUBLIC gtest gtest_main)

Basically, I've installed googletest into my home directory rather than system-wide. The find_package() command apparently succeeds. However, trying to build test_simple_tree fails with:

/usr/bin/ld: cannot find -lgtest
/usr/bin/ld: cannot find -lgtest_main

Inside this CMakeLists.txt, how else can I tell the linker to look elsewhere for the gtest?

EDIT: After reading the docs, I've fixed the Gtest issue as described below. However, the following issue cropped up: CMake imported target includes non-existent path

Solution

If find_package() was successful in finding the GTest includes/libraries, it should populate targets for you, per the CMake FindGTest documentation:

This module defines the following IMPORTED targets:

GTest::GTest: The Google Test gtest library, if found; adds Thread::Thread automatically

GTest::Main: The Google Test gtest_main library, if found

You should use these in your target_link_libraries() command instead. Also, CMake will populate GTEST_INCLUDE_DIRS, but the GTest include directories should be pulled in from the imported targets mentioned above.

---

Another important note: I'm not sure if you posted all of your CMake code, but I don't see a project() call in your code. As a result, the ${PROJECT_SOURCE_DIR} variable may not be what you expect. In general, it is good practice to declare your project with project() at the top of your CMake.

Your CMake file with these modifications could look something like this:

cmake_minimum_required(VERSION 3.15)

project(simple_tree_example)

set(CMAKE_CXX_STANDARD 17)

# adding library
set(ST_SRC simple_tree.cpp)
add_library(st ${ST_SRC})
target_include_directories(st PUBLIC 
    ${PROJECT_SOURCE_DIR}/include/data_structures/simple_tree/)

# adding googletest
set(GOOGLETEST_PATH ~/local/googletest)
set(GTEST_INCLUDE_DIR ~/local/include/)
set(GTEST_LIBRARY ~/local/lib/)
set(GTEST_MAIN_LIBRARY ~/local/lib/)
find_package(GTest REQUIRED)

# adding tests
set(TEST_TARGET test_simple_tree)
add_executable(${TEST_TARGET} test_simple_tree.cpp)
target_include_directories(${TEST_TARGET}
                        PUBLIC
                        ${PROJECT_SOURCE_DIR}/include/data_structures/simple_tree
                        ${GOOGLETEST_PATH})
target_link_libraries(${TEST_TARGET} PUBLIC st GTest::GTest GTest::Main)

Answered By - Kevin