.\" generated by cd2nroff 0.1 from CURLOPT_RESOLVER_START_DATA.md
.TH CURLOPT_RESOLVER_START_DATA 3 "2026-06-24" libcurl
.SH NAME
CURLOPT_RESOLVER_START_DATA \- pointer passed to the resolver start callback
.SH SYNOPSIS
.nf
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_RESOLVER_START_DATA,
                          void *pointer);
.fi
.SH DESCRIPTION
Pass a \fIpointer\fP is be untouched by libcurl and passed as the third
argument in the resolver start callback set with
\fICURLOPT_RESOLVER_START_FUNCTION(3)\fP.
.SH DEFAULT
NULL
.SH PROTOCOLS
This functionality affects all supported protocols
.SH EXAMPLE
.nf
static int resolver_start_cb(void *resolver_state, void *reserved,
                             void *userdata)
{
  (void)reserved;
  printf("Received resolver_state=%p userdata=%p\\n",
         resolver_state, userdata);
  return 0;
}

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_RESOLVER_START_FUNCTION, resolver_start_cb);
    curl_easy_setopt(curl, CURLOPT_RESOLVER_START_DATA, curl);
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
.fi
.SH AVAILABILITY
Added in curl 7.59.0
.SH RETURN VALUE
\fIcurl_easy_setopt(3)\fP returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non\-zero means an error occurred, see
\fIlibcurl\-errors(3)\fP.
.SH SEE ALSO
.BR CURLOPT_PREREQFUNCTION (3),
.BR CURLOPT_RESOLVER_START_FUNCTION (3)