未定义符号 _curl_easy_setopt 错误而 运行 示例代码

Question

我正在尝试测试 运行 curlpp 中的第一个示例，但出现错误 "Undefined symbol: _curl_easy_setopt"。我知道这是我尝试链接库的方式的问题。以下是我的方法。

header 搜索路径 -> 用于调试和发布 -> （我输入）/usr/local/include

库搜索路径 -> 用于调试和发布 ->（我输入）/usr/local/lib

其他链接器标志 -> 用于调试和发布 ->（我输入）-lcurlpp

我 运行 带有 API url 的例子我已经在 python 中成功地代替了 "example.com"。This is a picture of the full error .谢谢！`

#include <string>
#include <sstream>
#include <iostream>

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


namespace
{
const long MyPort = 80;
}

/**
 * This example is made to show you how you can use the Options.
 */
int main(int, char **)
{
    try
    {
        curlpp::Cleanup myCleanup;

        // First easy example.
        {
          // The first easiest example is to retreive the content of
          // a web page and put it in a stream.
          std::cout << curlpp::options::Url("https://www.alphavantage.co/query?function=TIME_SERIES_INTRADAY&symbol=VSLR&frequency=5min&outputsize=full&datatype=json&apikey=IGDV8B3MO9GQ9R35");

          // You don't need to use just the standard outputs. You
          // can use any stream:
          std::ostringstream os;
          os << curlpp::options::Url("https://www.alphavantage.co/query?function=TIME_SERIES_INTRADAY&symbol=VSLR&frequency=5min&outputsize=full&datatype=json&apikey=IGDV8B3MO9GQ9R35");
        }

        // More elaborate example.
        {
          // What the previous example done there was simply
          // to create a curlpp::Easy class, which is the basic
          // object in cURLpp, and then set the Url option.
          // curlpp::options classes are the primitives that allow to specify
          // values to the requests.
          curlpp::options::Url myUrl(std::string("https://www.alphavantage.co/query?function=TIME_SERIES_INTRADAY&symbol=VSLR&frequency=5min&outputsize=full&datatype=json&apikey=IGDV8B3MO9GQ9R35"));
          curlpp::Easy myRequest;
          myRequest.setOpt(myUrl);

          // Now that all the options we wanted to set are there, we need to
          // actually do the request. the "perform" method does actually that.
          // With that call, the request will be done and the content of that URL
          // will be printed in std::cout (which is the default).
          myRequest.perform();

          // If we wanted to put the content of the URL within a string stream
          // (or any type of std::ostream, for that matter), like the first example,
          // we would use the WriteStrem option like this:
          std::ostringstream os;
          curlpp::options::WriteStream ws(&os);
          myRequest.setOpt(ws);
          myRequest.perform();

          // There is some shorcut within curlpp that allow you to write shorter code
          // like this:
          os << myRequest;

          // That would do exactly what the previous code was doing.
        }

        // Creation of the URL option.
        curlpp::options::Url myUrl(std::string("https://www.alphavantage.co/query?function=TIME_SERIES_INTRADAY&symbol=VSLR&frequency=5min&outputsize=full&datatype=json&apikey=IGDV8B3MO9GQ9R35"));

        // Copy construct from the other URL.
        curlpp::options::Url myUrl2(myUrl);

        // Creation of the port option.
        curlpp::options::Port myPort(MyPort);

        // Creation of the request.
        curlpp::Easy myRequest;

        // Creation of an option that contain a copy of the URL option.
        curlpp::OptionBase *mytest = myUrl.clone();
        myRequest.setOpt(*mytest);

        // You can reuse the base option for other type of option
        // and set the option to the request. but first, don't forget
        // to delete the previous memory. You can delete it since the
        // option is internally duplicated for the request.
        delete mytest;
        mytest = myPort.clone();
        myRequest.setOpt(*mytest);
        delete mytest;

        // You can clone an option directly to the same type of
        // option.
        curlpp::options::Url *myUrl3 = myUrl.clone();
        myRequest.setOpt(myUrl3);
        // Now myUrl3 is owned by the request we will NOT use
        // it anymore.


        // You don't need to declare an option if you just want
        // to use it once.
        myRequest.setOpt(curlpp::options::Url("https://www.alphavantage.co/query?function=TIME_SERIES_INTRADAY&symbol=VSLR&frequency=5min&outputsize=full&datatype=json&apikey=IGDV8B3MO9GQ9R35"));


        // Note that the previous line wasn't really efficient
        // because we create the option, this option is duplicated
        // for the request and then the option destructor is called.
        // You can use this instead:
        myRequest.setOpt(new curlpp::options::Url("https://www.alphavantage.co/query?function=TIME_SERIES_INTRADAY&symbol=VSLR&frequency=5min&outputsize=full&datatype=json&apikey=IGDV8B3MO9GQ9R35"));
        // Note that with this the request will use directly this
        // instance we just created. Be aware that if you pass an
        // Option pointer to the setOpt function, it will consider
        // the instance has its own instance. The Option instance
        // will be deleted when the request will be deleted, so
        // don't use the instance further in your code.


        // Doing the previous line is efficient as this:
        myRequest.setOpt(myUrl.clone());


        // You can retreive the value of a specific option.
        std::cout << myUrl2.getValue() << std::endl;

        // Perform the transaction with the options set.
        myRequest.perform();
    }

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

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

  return 0;
}

Answer 1

缺失符号_curl_easy_setopt和curlpphomepage tells me that curlpp is a C++ wrapper around the C library libcurl.

因此您需要在编译时使用该库将 -lcurl 添加到 link。