---
name: "CURLOPT_RESOLVER_START_DATA"
section: "3"
platform: "linux"
package: "curl"
version: "8.23.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_RESOLVER_START_DATA"
---

# CURLOPT\_RESOLVER\_START\_DATA(3)

pointer passed to the resolver start callback

## 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)](/CURLOPT_RESOLVER_START_FUNCTION/3.md)*.

## DEFAULT

NULL

## PROTOCOLS

This functionality affects all supported 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) {
    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);
  }
}
```

## AVAILABILITY

Added in curl 7.59.0

## RETURN VALUE

*[curl\_easy\_setopt(3)](/curl_easy_setopt/3.md)* returns a CURLcode indicating success or error.

CURLE\_OK (0) means everything was OK, non-zero means an error occurred, see *[libcurl-errors(3)](/libcurl-errors/3.md)*.

## SEE ALSO

[**CURLOPT\_PREREQFUNCTION**(3)](/CURLOPT_PREREQFUNCTION/3.md), [**CURLOPT\_RESOLVER\_START\_FUNCTION**(3)](/CURLOPT_RESOLVER_START_FUNCTION/3.md)