CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_USE_GLOBAL_CACHE,
long enable);
Pass a long. If the enable value is 1, it tells curl to use a global DNS cache that will survive between easy handle creations and deletions. This is not thread-safe and this will use a global variable.
WARNING: this option is considered obsolete. Stop using it. Switch over to using the share interface instead! See CURLOPT_SHARE(3) and curl_share_init(3).
CURL *curl = curl_easy_init();
if(curl) {
CURLcode ret;
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
/* switch off the use of a global, thread unsafe, cache */
curl_easy_setopt(curl, CURLOPT_DNS_USE_GLOBAL_CACHE, 0L);
ret = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}