cmake无法链接可执行文件-LJSONCPP：没有使用github子模块的此类文件

Question

我正在一个使用JSONCPP进行解析和CMAKE进行编译的项目。我添加了JSONCPP官方git repository 作为我的项目的子模型subpoule添加repo_url外部/jsoncpp ，以使每个依赖关系保持在一起。

运行cmake -b out/build时，它正常工作。但是，当我做make时，我会收到以下错误：

/usr/bin/ld：找不到-ljsoncpp：no这样的文件或目录。

文件以下方式组织了：

- root
    - out/build
    - external
        - jsoncpp (cloned repo)
    - include
        foo.h
        bar.h
    - src
        foo.cpp
        bar.cpp
        main.cpp
    CMakeLists.txt

cmakelists.txt是这样：

cmake_minimum_required(VERSION 3.22.1)
project(ants)


# ".cpp" files in folder "src" into cmake variable "SOURCE"
file(GLOB SOURCE "src/*.cpp")

# Executable
add_executable(${PROJECT_NAME} ${SOURCE})

# Directory where cmake will look for include files
include_directories(include)

# Tells cmake to compile jsoncpp
add_subdirectory(external/jsoncpp)
# Tells cmake where to look for jsoncpp include files
target_include_directories(${PROJECT_NAME} 
    PUBLIC external/jsoncpp/include 
)

target_link_libraries(${PROJECT_NAME} jsoncpp)

Answer 1

jsoncppconfig.cmake定义属性interface_include_directories for targets jsoncpp_lib和JSONCPP_LIB_STATIC。

您需要查询目标属性并手动设置：

get_target_property(JSON_INC_PATH jsoncpp_lib INTERFACE_INCLUDE_DIRECTORIES)
include_directories(${JSON_INC_PATH})

链接是通过：

target_link_libraries(${PROJECT_NAME} jsoncpp_lib)

源。

尝试以下操作：

cmake_minimum_required(VERSION 3.22.1)
project(ants)

# ".cpp" files in folder "src" into cmake variable "SOURCE"
file(GLOB SOURCE "src/*.cpp")

# Executable
add_executable(${PROJECT_NAME} ${SOURCE})

# Directory where cmake will look for include files
include_directories(include)

# Tells cmake to compile jsoncpp
add_subdirectory(external/jsoncpp)
get_target_property(JSON_INC_PATH jsoncpp_lib INTERFACE_INCLUDE_DIRECTORIES)
include_directories(${JSON_INC_PATH})

target_link_libraries(${PROJECT_NAME} jsoncpp_lib)