---
name: "gnutls_x509_trust_list_set_getissuer_function"
section: "3"
platform: "linux"
package: "gnutls"
version: "3.8.13-3"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/gnutls_x509_trust_list_set_getissuer_function"
---

# gnutls\_x509\_trust\_list\_set\_getissuer\_function(3)

API function

## NAME

gnutls\_x509\_trust\_list\_set\_getissuer\_function - API function

## SYNOPSIS

**#include \<gnutls/x509.h\>**

**void gnutls\_x509\_trust\_list\_set\_getissuer\_function(gnutls\_x509\_trust\_list\_t** *tlist***, gnutls\_x509\_trust\_list\_getissuer\_function \*** *func***);**

## ARGUMENTS

- gnutls\_x509\_trust\_list\_t tlist

  is a **gnutls\_x509\_trust\_list\_t** type.

- gnutls\_x509\_trust\_list\_getissuer\_function \* func

  is the callback function

## DESCRIPTION

This function sets a callback to be called when the peer's certificate chain is incomplete due a missing intermediate certificate. The callback may provide the missing certificate for use during verification.

The callback's function prototype is defined in gnutls/x509.h as:

int (\*callback)(gnutls\_x509\_trust\_list\_t list, const gnutls\_x509\_crt\_t cert, gnutls\_x509\_crt\_t \*\*issuers, unsigned int \*issuers\_size);

If the callback function is provided then gnutls will call it during the certificate verification procedure. The callback may wish to use **gnutls\_x509\_crt\_get\_authority\_info\_access()** to get a URI from which to attempt to download the missing issuer certificate, if available.

On a successful call, the callback shall set '\*issuers' and '\*issuers\_size' even if the result is empty; in that case '\*issuers' will point to **NULL** and allocated using **gnutls\_x509\_crt\_list\_import2()**. The ownership of both the array and the elements is transferred to the caller and thus the application does not need to maintain the memory after the call.

The callback function should return 0 if the attempt to retrieve the issuer certificates for 'crt' succeeded, or non-zero to indicate any error occurred during the attempt. In the latter case, '\*issuers' and '\*issuers\_size' are not set.

## SINCE

3\.7.0

## REPORTING BUGS

Report bugs to \<bugs@gnutls.org\>.\
 Home page: https://www.gnutls.org

## COPYRIGHT

Copyright © 2001-2023 Free Software Foundation, Inc., and others.\
 Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved.

## SEE ALSO

The full documentation for **gnutls** is maintained as a Texinfo manual. If the /usr/share/doc/gnutls/ directory does not contain the HTML form visit

- https://www.gnutls.org/manual/