WordPress at a glance
function is not described

comment_guid() WP 2.5.0

Display the feed GUID for the current comment.

No Hooks.

Return

null. Nothing.

Usage

comment_guid( $comment_id );
$comment_id(int|WP_Comment)
Optional comment object or ID.
Default: global comment object

Changelog

Since 2.5.0 Introduced.

Code of comment_guid() WP 5.7.2

<?php
function comment_guid( $comment_id = null ) {
	echo esc_url( get_comment_guid( $comment_id ) );
}