Entry point could not be located in the dynamic link library - c++

Question

I created a DLL project in visual c++, and I wanted to use the cpprestsdk/casablanca.

Then I created a RestWrapper.h header file:

#pragma once

namespace mycpprest
{
    class RestWrapper
    {
    public:
        static __declspec(dllexport) void TestApi();
    };
}

And RestWrapper.cpp source file:

#include "stdafx.h"
#include "RestWrapper.h"

#include <cpprest/http_client.h>
#include <cpprest/filestream.h>
#include <cpprest/json.h>

using namespace utility;
using namespace web;
using namespace web::http;
using namespace web::http::client;
using namespace concurrency::streams;

namespace mycpprest
{
    void RestWrapper::TestApi()
    {
        auto fileStream = std::make_shared<ostream>();

        // Open stream to output file.
        pplx::task<void> requestTask = fstream::open_ostream(U("results.html")).then([=](ostream outFile)
        {
            *fileStream = outFile;

            // Create http_client to send the request.
            http_client client(U("http://13.231.231.252:3000/api/individual_employment_setting/detail/172"));

            // Build request URI and start the request.
            //uri_builder builder(U("/search"));
            //builder.append_query(U("q"), U("cpprestsdk github"));
            return client.request(methods::GET);
        })

        // Handle response headers arriving.
        .then([=](http_response response)
        {
            printf("Received response status code:%u\n", response.status_code());

            // Write response body into the file.
            // return response.body().read_to_end(fileStream->streambuf());
            stringstreambuf buffer;
            response.body().read_to_end(buffer).get();

            //show content in console
            printf("Response body: \n %s", buffer.collection().c_str());

            //parse content into a JSON object:
            //json::value jsonvalue = json::value::parse(buffer.collection());

            return  fileStream->print(buffer.collection()); //write to file anyway
        })

        // Close the file stream.
        .then([=](size_t)
        {
            return fileStream->close();
        });

        // Wait for all the outstanding I/O to complete and handle any exceptions
        try
        {
            requestTask.wait();
        }
        catch (const std::exception &e)
        {
            printf("Error exception:%s\n", e.what());
        }
    }
}

When I build it, It success built.

Then I created Windows Console Application in visual c++ to test the DLL project that I created.

I copy the MyCpprestDll.dll, MyCpprestDll.lib and RestWrapper.h from MycppestDll project into DllTest project.

Then in DllTest project properties, in the Linker->input->Additional Dependencies: I added MyCpprestDll.lib

And here the code of DllTest.cpp:

#include "stdafx.h"
#include "RestWrapper.h"
#include <iostream>

using namespace mycpprest;

int main()
{
    RestWrapper::TestApi();
    system("PAUSE");
    return 0;
}

It has no compile error, but when running the error says:

The procedure entry point ?TestApi@RestWrapper@mycpprest@@SAXXZ could not be located in the dynamic link library

I tried to search about the related issues but I don't know how to or what to set to my entry point in my dll project.

score 0 · Answer 1 · answered Apr 13 '18 at 08:17

0

You need to use dllexport when building your DLL, but dllimport when you are including it into another project

This answer shows you have to use some macros and pre-processor definitions to make it work.

answered Apr 13 '18 at 08:17

Sean

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Amit Rastogi · Answer 2 · 2018-04-14T16:04:20.100

In your RestWrapper.h header file do something as shown below. Note that you must use __declspec(dllimport) for the importing executable to access the DLL's public data symbols and objects. Also, make sure you define the macro RestWrapper_EXPORTS in C/C++->Preprocessor->Preprocessor Definitions in your DLL project properties.

#ifdef RestWrapper_EXPORTS
#define RestWrapper_APIS __declspec(dllexport)
#else
#define RestWrapper_APIS __declspec(dllimport)
#endif

namespace mycpprest
{
 // This class is exported from the RestWrapper.dll
 class RestWrapper 
 {
   public:
    static RestWrapper_APIS void TestApi();     
 };
}

Rebuild your DLL project. No changes needed in your DllTest project, just compile your DllTest project using the updated RestWrapper.h and RestWrapper.lib file.

Entry point could not be located in the dynamic link library - c++

2 Answers2