CMake conflict with multiple gtest

问题:

This is my first post on StackOverflow, so apologies if there's something wrong with my question.

I'm new at CMake, and I'm running into a problem trying to import gtest (Google Test) in a C++ project with an existing gtest directory used within a library.

My root CMakeLists.txt file is this (My changes are made between "Begin changes" and "End changes") :

cmake_minimum_required(VERSION 2.6)  project(nifi-minifi-cpp) set(PROJECT_NAME "nifi-minifi-cpp") set(PROJECT_VERSION_MAJOR 0) set(PROJECT_VERSION_MINOR 2) set(PROJECT_VERSION_PATCH 0)  #### Establish Project Configuration #### # Enable usage of the VERSION specifier # https://cmake.org/cmake/help/v3.0/policy/CMP0048.html#policy:CMP0048 IF(POLICY CMP0048)   CMAKE_POLICY(SET CMP0048 OLD) ENDIF(POLICY CMP0048)  include(CheckCXXCompilerFlag) CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11) CHECK_CXX_COMPILER_FLAG("-std=c++0x" COMPILER_SUPPORTS_CXX0X) if(COMPILER_SUPPORTS_CXX11)     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11") elseif(COMPILER_SUPPORTS_CXX0X)     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x") else()         message(STATUS "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.") endif()  set(CMAKE_CXX_STANDARD 11) set(CMAKE_CXX_STANDARD_REQUIRED ON)  # Search for threads find_package(Threads REQUIRED)  # Provide custom modules for the project list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")  add_subdirectory(thirdparty/yaml-cpp-yaml-cpp-0.5.3) add_subdirectory(libminifi) add_subdirectory(main)  # Generate source assembly set(ASSEMBLY_BASE_NAME "${CMAKE_PROJECT_NAME}-${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}.${PROJECT_VERSION_PATCH}") set(CPACK_SOURCE_GENERATOR "TGZ") set(CPACK_SOURCE_PACKAGE_FILE_NAME "${ASSEMBLY_BASE_NAME}-source") set(CPACK_SOURCE_IGNORE_FILES "/build/;~$;${CPACK_SOURCE_IGNORE_FILES};${CMAKE_SOURCE_DIR}/.git/;${CMAKE_SOURCE_DIR}/.idea/;${CMAKE_SOURCE_DIR}/cmake-build-debug/")  # Generate binary assembly install(FILES conf/minifi.properties conf/config.yml         DESTINATION conf         COMPONENT bin)  install(PROGRAMS bin/minifi.sh         DESTINATION bin         COMPONENT bin)  install(FILES LICENSE README.md NOTICE         DESTINATION .         COMPONENT bin)  set(CPACK_GENERATOR "TGZ") set(CPACK_COMPONENT_INCLUDE_TOPLEVEL_DIRECTORY 1) set(CPACK_PACKAGE_DESCRIPTION_SUMMARY "Apache NiFi MiNiFi C++ version ${VERSION}") set(CPACK_PACKAGE_VENDOR "Apache NiFi") set(CPACK_PACKAGE_DESCRIPTION_FILE "${CMAKE_CURRENT_SOURCE_DIR}/README.md") set(CPACK_RESOURCE_FILE_LICENSE "${CMAKE_CURRENT_SOURCE_DIR}/LICENSE") set(CPACK_PACKAGE_FILE_NAME "${ASSEMBLY_BASE_NAME}") set(CPACK_BINARY_TGZ, "ON")  set(CPACK_ARCHIVE_COMPONENT_INSTALL ON) set(CPACK_COMPONENTS_ALL bin)  include(CPack)  #### Begin changes # Set up testing enable_testing() set(GTEST_ROOT "thirdparty/googletest/googletest") add_subdirectory(thirdparty/googletest) # find_package(GTest REQUIRED) include_directories(${GTEST_INCLUDE_DIRS}) add_executable(tailFileTest         test/TailFileTest.cpp         ) target_link_libraries(tailFileTest  ${GTEST_LIBRARY_DEBUG} ${GTEST_MAIN_LIBRARY_DEBUG})  add_test(         NAME tailFileTest         COMMAND tailFileTest )   #add_dependencies(${PROJECT_TEST_NAME} googletest)  #set(PROJECT_TEST_NAME ${PROJECT_NAME}_test) #file(GLOB TEST_SRC_FILES ${PROJECT_SOURCE_DIR}/test/*.cpp) # #add_executable(${PROJECT_TEST_NAME} ${TEST_SRC_FILES}) #add_dependencies(${PROJECT_TEST_NAME} googletest) #### End changes 

And output from CMake when running cmake .. (the more relevant error message - probably) is:

CMake Error at thirdparty/googletest/googletest/cmake/internal_utils.cmake:151 (add_library):   add_library cannot create target "gtest" because another target with the   same name already exists.  The existing target is a static library created   in source directory   "/home/dev/nifi-minifi-cpp/thirdparty/yaml-cpp-yaml-cpp-0.5.3/test/gmock-1.7.0/gtest".   See documentation for policy CMP0002 for more details. 

Currently, I've got a copy of googletest in:

/home/g/dev/nifi-minifi-cpp/thirdparty/googletest 

And the existing googletest directory is within:

/home/g/dev/nifi-minifi-cpp/thirdparty/yaml-cpp-yaml-cpp-0.5.3/test/gmock-1.7.0 

Here's a quick picture of the directory structure:

The overall goal is to have a test directory for running tests.

Any suggestions or clues to what I'm doing wrong, or what I should be doing, would be greatly appreciated. Hopefully the above explains the challenge I'm facing, and if there's a file or error message people think I'm missing that would help I can paste it in here.

回答1:

This is just double including 3d-party project (gtest in your case) using add_subdirectory. The first include point is

add_subdirectory(gmock-1.7.0)     

inside yaml-cpp subproject and the second include point is

add_subdirectory(thirdparty/googletest) 

in your CMakeLists.txt.

Such double including doesn't work in CMake, so you need to eliminate one of add_subdirectory call.

1. In your code, you may replace add_subdirectory approach by combination of ExternalProject_Add and execute_process. That approach will build googletest on configuration stage (so, find_package(GTest) will work), but doesn't pollute namespace of your project with targets from googletest.

2. In other project (yaml-cpp), you may eliminate including googletest by disable testing. Just disable appropriate option

   option(YAML_CPP_BUILD_TOOLS "Enable testing and parse tools" OFF) 

   before

   add_subdirectory(thirdparty/yaml-cpp-yaml-cpp-0.5.3) 

   (For disabling option from CMakeLists.txt you need to reconfigure the whole project cleanly, that is with empty CMake cache).

   Note, that this option also disables some utilities under util/ subdirectory of yaml-cpp project.

3. Similarly to the first approach, you may change inclusion of yaml-cpp subproject to ExternalProject_Add + execute_process. Such a way all its targets and targets of its subprojects will not pollute namespace of your project.

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