如何使用 cmake link jsoncpp

Question

我找不到使用我的可执行文件 link jsoncpp 的方法。我尝试了很多东西，但 none 成功了：

linking jsoncpp_lib
也写了什么here

我想使用ubuntu自带的jsoncpp库。有没有人设法做到这一点？

$ ls /usr/lib/x86_64-linux-gnu/libjsoncpp.*

/usr/lib/x86_64-linux-gnu/libjsoncpp.a   /usr/lib/x86_64-linux-gnu/libjsoncpp.so.1
/usr/lib/x86_64-linux-gnu/libjsoncpp.so  /usr/lib/x86_64-linux-gnu/libjsoncpp.so.1.7.4

CMakeLists.txt

cmake_minimum_required(VERSION 3.8.0 FATAL_ERROR)

project(jsoncpp_example)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17 -stdlib=libc++ -Wall -Werror")
set(CMAKE_EXE_LINKER_FLAGS "-lstdc++ -lpthread")

add_executable(parse main.cpp)
target_include_directories(parse PRIVATE include)
target_link_libraries(parse jsoncpp)

Parser.h

#ifndef MY_PARSER_H
#define MY_PARSER_H

#include <vector>
#include <fstream>
#include <jsoncpp/json/json.h>

class MyParser {
public:
    MyParser() = default;
    ~MyParser() = default;
    
    inline static 
    Json::Value parse(const char* inputFile) {
        Json::Value val;
        std::ifstream ifs(inputFile);
        Json::Reader reader;
        reader.parse(ifs, val);
        return val;
    }

};

#endif /* MY_PARSER_H */

main.cpp

#include <iostream>
#include "Parser.h"

int main(){
    Json::Value val = MyParser::parse("input.json");
    std::cout << val["name"] << std::endl;
}

Ubuntu 18.04，用clan-8.0编译

CXX=clang-8 cmake ..
make -j

我得到的错误

Scanning dependencies of target parse
[ 50%] Building CXX object CMakeFiles/parse.dir/main.cpp.o
[100%] Linking CXX executable parse
CMakeFiles/parse.dir/main.cpp.o: In function `main':
main.cpp:(.text+0x3e): undefined reference to `Json::operator<<(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, Json::Value const&)'
CMakeFiles/parse.dir/main.cpp.o: In function `MyParser::parse(char const*)':
main.cpp:(.text._ZN8MyParser5parseEPKc[_ZN8MyParser5parseEPKc]+0x349): undefined reference to `Json::Reader::parse(std::__1::basic_istream<char, std::__1::char_traits<char> >&, Json::Value&, bool)'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
CMakeFiles/parse.dir/build.make:94: recipe for target 'parse' failed
make[2]: *** [parse] Error 1
CMakeFiles/Makefile2:67: recipe for target 'CMakeFiles/parse.dir/all' failed
make[1]: *** [CMakeFiles/parse.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2

Answer 1

wiki 提到

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

target_link_libraries(${PROJECT_NAME} jsoncpp_lib)

但我自己无法让它工作。如果您将 jsoncpp .cmake 文件安装在自动搜索的位置，这可能是一个选项：

cmake_minimum_required(VERSION 3.8.0 FATAL_ERROR)

project(jsoncpp_example)

find_package(PkgConfig REQUIRED)
pkg_check_modules(JSONCPP jsoncpp)

set(CMAKE_THREAD_PREFER_PTHREAD TRUE) # these are to use the prefered -pthread flag
set(THREADS_PREFER_PTHREAD_FLAG TRUE) # over the -lpthread option
find_package(Threads REQUIRED)

add_executable(parse main.cpp)
set_property(TARGET parse PROPERTY CXX_STANDARD 17)
target_compile_options(parse PRIVATE -Wall -Werror)

target_link_libraries(parse PRIVATE Threads::Threads ${JSONCPP_LIBRARIES})

Answer 2

在 Linux 这对我有用

安装开发库。

sudo apt-get 安装 libjsoncpp-dev
在 cmakelists 中。

pkg_search_module(JSONCPP jsoncpp)

添加到...

TARGET_LINK_LIBRARIES(${JSONCPP_LIBRARIES})

cmake .
制作

Answer 3

对于那些像我一样来到这个主题的人，他们正在寻找一种方法来使用 cmake 在 C++ 项目中包含 jsoncpp 库。我通过克隆 vcpkg repository into an external folder and installing the jsoncpp package through vcpkg, as the official jsoncpp repository suggests. I've better described the solution to this problem in this topic here 解决了这个问题，因为它在搜索方面更通用。

Answer 4

我用 cmake 3.22 让它工作：

find_package(jsoncpp REQUIRED)
...
target_link_libraries({app_name} ... jsoncpp_lib)

如何使用 cmake link jsoncpp

How to link jsoncpp with cmake

c++

json

linux

cmake

jsoncpp