get_comment_guid( int|WP_Comment $comment_id = null )

Source

File: wp-includes/feed.php

function get_comment_guid( $comment_id = null ) {
	$comment = get_comment( $comment_id );

	if ( ! is_object( $comment ) ) {
		return false;
	}

	return get_the_guid( $comment->comment_post_ID ) . '#comment-' . $comment->comment_ID;
}