conflict with gflags already exists

[Wsine]

I have a project which depends on both gflags and glog. I include them in my CMakeLists.txt file as below.

cmake_minimum_required(VERSION 3.0)
project(Test)

add_subdirectory(thirdparty/gflags)
add_subdirectory(thirdparty/glog)

add_executable(Test main.cc)
target_link_libraries(Test pcanbasic gflags glog)

this comes an error:

$ cmake ..
-- The C compiler identification is GNU 4.8.4
-- The CXX compiler identification is GNU 4.8.4
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Looking for C++ include unistd.h
-- Looking for C++ include unistd.h - found
-- Looking for C++ include stdint.h
-- Looking for C++ include stdint.h - found
-- Looking for C++ include inttypes.h
-- Looking for C++ include inttypes.h - found
-- Looking for C++ include sys/types.h
-- Looking for C++ include sys/types.h - found
-- Looking for C++ include sys/stat.h
-- Looking for C++ include sys/stat.h - found
-- Looking for C++ include fnmatch.h
-- Looking for C++ include fnmatch.h - found
-- Looking for C++ include stddef.h
-- Looking for C++ include stddef.h - found
-- Check size of uint32_t
-- Check size of uint32_t - done
-- Looking for strtoll
-- Looking for strtoll - found
CMake Error at /usr/local/lib/cmake/gflags/gflags-targets.cmake:34 (message):
  Some (but not all) targets in this export set were already defined.

  Targets Defined: gflags_nothreads_static

  Targets not yet defined: gflags_static

Call Stack (most recent call first):
  /usr/local/lib/cmake/gflags/gflags-config.cmake:10 (include)
  thirdparty/glog/CMakeLists.txt:54 (find_package)


-- Configuring incomplete, errors occurred!
See also "/home/weizhengyuan/Workspace/CanBusTest/build/CMakeFiles/CMakeOutput.log".

are there any solution?
BR

[Wsine]

Should it be a if(NOT TARGET gflags) judgement arround glog/CMakeLists.txt:54?

[sergiud]

Take a look at CMake's ExternalProject module. This is the proper way of integrating local dependencies.

[EZ4NO1]

have you solved the problem yet

[Bill0412]

add_subdirectory(third/gflags)
if(NOT TARGET gflags)
        add_subdirectory(third/glog)
endif()

This solves the problem

[grawert]

Using ExternalProject solves the problem well. It allows defining dependencies between the projects.

• Define external projects

# Build gflags as an external project.
set(GFLAGS_INSTALL_DIR ${CMAKE_BINARY_DIR}/libs/gflags)
set(GFLAGS_INCLUDE_DIR ${GFLAGS_INSTALL_DIR}/include)
set(GFLAGS_LIB_DIR ${GFLAGS_INSTALL_DIR}/lib)
ExternalProject_Add(gflags_external_project
    SOURCE_DIR  ${CMAKE_SOURCE_DIR}/libs/gflags
    PREFIX      ${GFLAGS_INSTALL_DIR}
    INSTALL_DIR ${GFLAGS_INSTALL_DIR}
    CMAKE_ARGS  -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
                -DCMAKE_CXX_FLAGS=${EXTERNAL_PROJECT_CMAKE_CXX_FLAGS}
                -DCMAKE_INSTALL_PREFIX:PATH=${GFLAGS_INSTALL_DIR}
                -DBUILD_SHARED_LIBS=${BUILD_SHARED_LIBS}
                )
include_directories(BEFORE SYSTEM ${GFLAGS_INCLUDE_DIR})
link_directories(${GFLAGS_LIB_DIR})

# Build glog as an external project.
set(GLOG_INSTALL_DIR ${CMAKE_BINARY_DIR}/libs/glog)
set(GLOG_INCLUDE_DIR ${GLOG_INSTALL_DIR}/include)
set(GLOG_LIB_DIR ${GLOG_INSTALL_DIR}/lib)
ExternalProject_Add(glog_external_project
    SOURCE_DIR  ${CMAKE_SOURCE_DIR}/libs/glog
    PREFIX      ${GLOG_INSTALL_DIR}
    INSTALL_DIR ${GLOG_INSTALL_DIR}
    CMAKE_ARGS  -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}
                -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
                -DCMAKE_CXX_FLAGS=${EXTERNAL_PROJECT_CMAKE_CXX_FLAGS}
                -DCMAKE_INSTALL_PREFIX:PATH=${GLOG_INSTALL_DIR}
                -DBUILD_SHARED_LIBS=${BUILD_SHARED_LIBS}
    DEPENDS     gflags_external_project
    )
include_directories(BEFORE SYSTEM ${GLOG_INCLUDE_DIR})
link_directories(${GLOG_LIB_DIR})

• Define the dependencies for your target and link against the libraries

add_dependencies(my_program
    gflags_external_project
    glog_external_project
    )
target_link_libraries(my_program pthread gflags glog)

As taken from the fuchsia/cobalt project.