CURLOPT_TRAILERDATA - pointer passed to trailing headers callback
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TRAILERDATA, void *userdata);
Data pointer to be passed to the HTTP trailer callback function.
/* Assuming we have a CURL handle in the hndl variable. */
struct MyData data;
curl_easy_setopt(hndl, CURLOPT_TRAILERDATA, &data);
A more complete example can be found in
This option was added in curl 7.64.0 and is present if HTTP support is enabled