Libcurl hangs on curl_easy_perform or curl_multi_perform never decrease second parameter - dll

Question

I have an issue – There is an application (P) which create an instance of the com component (F) which make calls from separate dll (U).
P(app)—CoCreateInstance()--->F(com .dll)-----(call)--->U(MFC extension.dll)------(call libcurl.dll)
I create small test console application
#include "stdafx.h"
#include <iostream>
#include "curl/curl.h"
static std::string readBuffer;
static size_t WriteCallback(void *contents, size_t size, size_t nmemb, void *userp)
{
size_t realsize = size * nmemb;
readBuffer.append((const char*)contents, realsize);
return realsize;
}
int blocking_curl()
{
const std::string endPointUrl = "https://somecoolserver.com/resource";
const std::string urlparam = "param1=pValue1&param2=pValue2& param3=pValue3 ";
const std::string cookie = "";
const std::string httpHeadAccept = "application/xml";
const std::string httpContentType = "Content-Type: application/x-www-form-urlencoded";
const std::string AuthCertficate = "";
const std::string OAuthToken = "";
CURL *curl = NULL;
CURLcode res = CURLE_FAILED_INIT;
struct curl_slist *headers = NULL;
curl = curl_easy_init();
if(!curl)
{
return res;
}
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "POST");
curl_easy_setopt(curl, CURLOPT_URL, endPointUrl.c_str());
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, urlparam.c_str());
curl_easy_setopt(curl, CURLOPT_DEFAULT_PROTOCOL, "https");
headers = curl_slist_append(headers, httpHeadAccept.c_str());
headers = curl_slist_append(headers, httpContentType.c_str());
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, errbuf);
headers = curl_slist_append(headers, OAuthToken.c_str());
readBuffer.clear();
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteCallback);
if (!cookie.empty())
{
headers = curl_slist_append(headers, AuthCertficate.c_str());
std::string pCookie = "somestring=";
pCookie += cookie;
curl_easy_setopt(curl, CURLOPT_COOKIE, pCookie.c_str());
}
else
{
headers = curl_slist_append(headers, OAuthToken.c_str());
}
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
std::cout << "Response: " << readBuffer.c_str() << std::endl;
return res;
}
int _tmain(int argc, _TCHAR* argv[])
{
blocking_curl();
return 0;
}
This code works fine and I get in readBuffer the exact a such result as I expect.
However, if I directly copy this code to my U dll (more exactly replace such a code within called function) this code hangs on curl_easy_perform. Version of libcurl 7.54.0. I see in debugger all correct flow and call stack – but in U dll it hangs on curl_easy_perform. I even have no idea how it is possible! In debugger I see libcurl.dll is loaded and the version (7.54.0) is correct. All parameters are hardcoded (url, url parameters and so on) but in one case it works and for another doesn’t! Additionally I created another function with multi interface but it is also doesn’t work.
I have two ideas:
The com component load U dll and U dll try to load libcurl.dll somewhere from the system. My searching through the file system shows there is several version of libcurl.dll in the system. One for MacAfee antivirus and one in Microsoft office. However if I put the call curl_version() before curl_easy_perform I see as a result correct version. I can’t 100% be sure it is correct because this string may be get on compile time but actually it load libcurl of the other version.
Com component may have different address space and U dll actually can’t find the library. I also thing it is correct because all other calls are correct including curl_init..
But what else?! If somebody have any ideas please share.

Answer 1

The issue was a result of call the function of dll (U) with libcurl code in InitInstance method of dll F (COM component). After moving all libcurl routine to the other working methods everything have worked fine.