Source

File: wp-includes/link-template.php

function get_page_link( $post = false, $leavename = false, $sample = false ) {
	$post = get_post( $post );

	if ( 'page' === get_option( 'show_on_front' ) && get_option( 'page_on_front' ) == $post->ID ) {
		$link = home_url( '/' );
	} else {
		$link = _get_page_link( $post, $leavename, $sample );
	}

	/**
	 * Filters the permalink for a page.
	 *
	 * @since 1.5.0
	 *
	 * @param string $link    The page's permalink.
	 * @param int    $post_id The ID of the page.
	 * @param bool   $sample  Is it a sample permalink.
	 */
	return apply_filters( 'page_link', $link, $post->ID, $sample );
}