---

c: Copyright (C) Daniel Stenberg, daniel@haxx.se, et al. SPDX-License-Identifier: curl Title: CURLOPT_RESOLVER_START_DATA Section: 3 Source: libcurl See-also:

• CURLOPT_PREREQFUNCTION (3)
• CURLOPT_RESOLVER_START_FUNCTION (3) Protocol:
• All Added-in: 7.59.0

---

NAME

CURLOPT_RESOLVER_START_DATA - pointer passed to the resolver start callback

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_RESOLVER_START_DATA,
                          void *pointer);

DESCRIPTION

Pass a pointer is be untouched by libcurl and passed as the third argument in the resolver start callback set with CURLOPT_RESOLVER_START_FUNCTION(3).

DEFAULT

NULL

%PROTOCOLS%

EXAMPLE

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) {
    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");
    curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

%AVAILABILITY%

RETURN VALUE

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).