curl_free man page
curl_free — reclaim memory that has been obtained through a libcurl call
void curl_free( char *ptr );
curl_free reclaims memory that has been obtained through a libcurl call. Use curl_free(3) instead of free() to avoid anomalies that can result from differences in memory management between your application and libcurl.
Passing in a NULL pointer in ptr will make this function return immediately with no action.
curl_easy_escape(3), curl_easy_unescape(3), curl_escape(3), curl_unescape(3), curl_url_get(3), libcurl-url(3).