Source

File: wp-includes/comment-template.php

function get_comment_link( $comment = null, $args = array() ) {
	global $wp_rewrite, $in_comment_loop;

	$comment = get_comment( $comment );

	// Back-compat.
	if ( ! is_array( $args ) ) {
		$args = array( 'page' => $args );
	}

	$defaults = array(
		'type'      => 'all',
		'page'      => '',
		'per_page'  => '',
		'max_depth' => '',
		'cpage'     => null,
	);
	$args     = wp_parse_args( $args, $defaults );

	$link = get_permalink( $comment->comment_post_ID );

	// The 'cpage' param takes precedence.
	if ( ! is_null( $args['cpage'] ) ) {
		$cpage = $args['cpage'];

		// No 'cpage' is provided, so we calculate one.
	} else {
		if ( '' === $args['per_page'] && get_option( 'page_comments' ) ) {
			$args['per_page'] = get_option( 'comments_per_page' );
		}

		if ( empty( $args['per_page'] ) ) {
			$args['per_page'] = 0;
			$args['page']     = 0;
		}

		$cpage = $args['page'];

		if ( '' == $cpage ) {
			if ( ! empty( $in_comment_loop ) ) {
				$cpage = get_query_var( 'cpage' );
			} else {
				// Requires a database hit, so we only do it when we can't figure out from context.
				$cpage = get_page_of_comment( $comment->comment_ID, $args );
			}
		}

		/*
		 * If the default page displays the oldest comments, the permalinks for comments on the default page
		 * do not need a 'cpage' query var.
		 */
		if ( 'oldest' === get_option( 'default_comments_page' ) && 1 === $cpage ) {
			$cpage = '';
		}
	}

	if ( $cpage && get_option( 'page_comments' ) ) {
		if ( $wp_rewrite->using_permalinks() ) {
			if ( $cpage ) {
				$link = trailingslashit( $link ) . $wp_rewrite->comments_pagination_base . '-' . $cpage;
			}

			$link = user_trailingslashit( $link, 'comment' );
		} elseif ( $cpage ) {
			$link = add_query_arg( 'cpage', $cpage, $link );
		}
	}

	if ( $wp_rewrite->using_permalinks() ) {
		$link = user_trailingslashit( $link, 'comment' );
	}

	$link = $link . '#comment-' . $comment->comment_ID;

	/**
	 * Filters the returned single comment permalink.
	 *
	 * @since 2.8.0
	 * @since 4.4.0 Added the `$cpage` parameter.
	 *
	 * @see get_page_of_comment()
	 *
	 * @param string     $link    The comment permalink with '#comment-$id' appended.
	 * @param WP_Comment $comment The current comment object.
	 * @param array      $args    An array of arguments to override the defaults.
	 * @param int        $cpage   The calculated 'cpage' value.
	 */
	return apply_filters( 'get_comment_link', $link, $comment, $args, $cpage );
}