将 curlpp 添加到 cmake 项目答案

【问题标题】：Add curlpp to cmake project将 curlpp 添加到 cmake 项目
【发布时间】：2019-11-26 17:26:56
【问题描述】：

我正在尝试在 curlcpp 和 cmake 的帮助下用 C++ 做一个项目，但我无法编译该项目。

我是 CMakeLists 的新手，很难理解如何添加使项目正常运行所需的内容。我基本上通常在没有真正了解它们的工作原理的情况下复制我在其他帖子中可以找到的内容；教程和文档通常要么太基础，要么太复杂。更糟糕的是，我的印象是每个库的添加方式都不同，所以当有一个新的库要添加时，我必须添加它的唯一方法是搜索以前的帖子询问如何做。在这种情况下，我找不到任何对我有帮助的东西。

这就是我所做的：

用自制软件安装 curlpp 和 curl 后

brew install curl
brew install curlpp

我写我的项目：

Cmakelists.txt：

cmake_minimum_required(VERSION 3.0)

project(stock_analysis)

set(CMAKE_CXX_FLAGS "-g -Wall -std=c++11")


######## BOOST STUFF ########
#DELETE NEXT LINE
set(Boost_NO_BOOST_CMAKE ON)

# set(Boost_USE_STATIC_LIBS        ON) # only find static libs
# set(Boost_USE_MULTITHREADED      ON)
# set(Boost_USE_STATIC_RUNTIME    OFF)
find_package(Boost COMPONENTS
                   filesystem
)

######## CURL STUFF ########
include(FindCURL)
find_package(CURL REQUIRED)
if(CURL_FOUND)
 message(STATUS "Found CURL version: ${CURL_VERSION_STRING}")
 message(STATUS "Using CURL include dir(s): ${CURL_INCLUDE_DIRS}")
 message(STATUS "Using CURL lib(s): ${CURL_LIBRARIES}")
else()
 message(FATAL_ERROR "Could not find CURL")
endif()




SET(HEADERS
   include
)

SET(SOURCE_FILES
  src/main.cpp
  src/analyse.cpp
  src/helpers.cpp
  src/simulation.cpp
  src/data.cpp
)

include_directories(${HEADERS}
                   ${Boost_INCLUDE_DIRS}
                   ${CURL_INCLUDE_DIRS}
)

add_executable(app ${SOURCE_FILES})

target_link_libraries(app
       ${Boost_LIBRARIES}
       ${CURL_LIBRARIES}
)

data.cpp中的功能（我基本上是复制curcpp网页中的例子）：

#include "data.h"

#include <iostream>

#include <curlpp/cURLpp.hpp>
#include <curlpp/Easy.hpp>
#include <curlpp/Options.hpp>

using namespace curlpp::options;


void fetchData(){

  try
    {
    // That's all that is needed to do cleanup of used resources (RAII style).
        curlpp::Cleanup myCleanup;

        // Our request to be sent.
        curlpp::Easy myRequest;

        // Set the URL.
        myRequest.setOpt<Url>("http://example.com");

        // Send request and get a result.
        // By default the result goes to standard output.
        myRequest.perform();
  }

  catch( curlpp::RuntimeError &e )
    {
        std::cout << e.what() << std::endl;
    }

    catch( curlpp::LogicError &e )
    {
        std::cout << e.what() << std::endl;
    }
}

我得到的错误：

Undefined symbols for architecture x86_64:
  "curlpp::OptionBase::OptionBase(CURLoption)", referenced from:
      curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::Option(CURLoption, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in data.cpp.o
  "curlpp::OptionBase::~OptionBase()", referenced from:
      curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::Option(CURLoption, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in data.cpp.o
      curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::~Option() in data.cpp.o
  "curlpp::UnsetOption::UnsetOption(char const*)", referenced from:
      curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::updateMeToOption(curlpp::OptionBase const&) in data.cpp.o
      curlpp::OptionTrait<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, (CURLoption)10002>::updateHandleToMe(curlpp::internal::CurlHandle*) const in data.cpp.o
      curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::getValue() const in data.cpp.o
  "curlpp::RuntimeError::~RuntimeError()", referenced from:
      curlpp::UnsetOption::~UnsetOption() in data.cpp.o
  "curlpp::libcurlRuntimeAssert(char const*, CURLcode)", referenced from:
      void curlpp::internal::CurlHandle::option<void*>(CURLoption, void*) in data.cpp.o
  "curlpp::Easy::perform()", referenced from:
      StockAnalysis::fetchData(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, bool const&) in data.cpp.o
  "curlpp::Easy::Easy()", referenced from:
      StockAnalysis::fetchData(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, bool const&) in data.cpp.o
  "curlpp::Easy::~Easy()", referenced from:
      StockAnalysis::fetchData(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, bool const&) in data.cpp.o
  "curlpp::Cleanup::Cleanup()", referenced from:
      StockAnalysis::fetchData(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, bool const&) in data.cpp.o
  "curlpp::Cleanup::~Cleanup()", referenced from:
      StockAnalysis::fetchData(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, bool const&) in data.cpp.o
  "curlpp::OptionBase::operator<(curlpp::OptionBase const&) const", referenced from:
      vtable for curlpp::OptionTrait<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, (CURLoption)10002> in data.cpp.o
      vtable for curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > in data.cpp.o
  "typeinfo for curlpp::LogicError", referenced from:
      GCC_except_table0 in data.cpp.o
  "typeinfo for curlpp::OptionBase", referenced from:
      curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::updateMeToOption(curlpp::OptionBase const&) in data.cpp.o
      typeinfo for curlpp::Option<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > in data.cpp.o
  "typeinfo for curlpp::RuntimeError", referenced from:
      GCC_except_table0 in data.cpp.o
      typeinfo for curlpp::UnsetOption in data.cpp.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [app] Error 1
make[1]: *** [CMakeFiles/app.dir/all] Error 2
make: *** [all] Error 2

我之前关注过下一个帖子： Linking curl in a project using CMake

将 curlcpp 添加到 cmakelists 中的 target_link_libraries() 只会出现另一个错误：


ld: library not found for -lcurlpp
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [app] Error 1
make[1]: *** [CMakeFiles/app.dir/all] Error 2
make: *** [all] Error 2

顺便说一句，我不明白为什么 curlcpp 在没有传统 cmakelist 表示法的情况下无处出现 ${Some_variable}

【问题讨论】：

您链接的是 cURL 库，而不是 cURLpp 库，它与 cURL 不同。
@squareskittles 我尝试按照链接中的信息进行操作，但它不起作用。我也会编辑问题以添加错误。
我认为您可能希望将库导入 CMake，或者至少告诉 CMake 在哪里查找已安装的库。查看this问题的答案。
该解决方案确实有效，但它一点也不优雅也不便携。调用 link_directories(/usr/local/Cellar/curlpp/0.8.1/lib/) 是 homebrew 安装库的位置使编译工作。但是我仍然不明白为什么我必须放入 target_link_libraries curlpp 而不是 libcurlpp 这是库的名称（可以在路径上找到 libcurlpp.a 和 libcurlpp.dylib）
@Alexis 库 curlpp 不支持与 CMake 一起使用，不幸的是。您必须将支持添加到库中或编写查找模块文件。这些都不是一件容易的事，但你可以在那里找到更多信息：It's Time To Do CMake Right

标签： c++ curl cmake curlpp

【解决方案1】：

使用 curlpp 如下（最少代码）：

cmake_minimum_required(VERSION 3.14)
project(testCurlPP LANGUAGES CXX)
set(CMAKE_INCLUDE_CURRENT_DIR ON)
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

include(FindPkgConfig)
pkg_check_modules(CURLPP REQUIRED curlpp)

add_executable(testCurlPP
  main.cpp
)
target_link_libraries(testCurlPP
    ${CURLPP_LDFLAGS}
    )

注意：在项目中使用之前不要忘记构建和安装 curlpp。

构建（获取最新版本）curlpp:

mkdir build
cd build
cmake ..
make -j8
sudo make install

将其位置添加到环境变量中：

LD_LIBRARY_PATH=/usr/local/lib

【讨论】：