I intend to do https requests with libcurl and openssl with a C++ program.
I initialized libcurl with curl_global_init(CURL_GLOBAL_ALL) as described in the
curl_global_init(CURL_GLOBAL_ALL)
As the descibed in this answer, you might need to disable SSLv3 if you are on Ubuntu 16.04 like so
curl_easy_setopt(curl_, CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1_2));
It was disabled on Ubuntu 16.04 for security reasons, see more here.