wp-includes/comment-template.php:1251Displays the current post's trackback URL.
$deprecated_echobooloptionaltruevoid|stringfunction trackback_url( $deprecated_echo = true ) { if ( true !== $deprecated_echo ) { _deprecated_argument( __FUNCTION__, '2.5.0', sprintf( /* translators: %s: get_trackback_url() */ __( 'Use %s instead if you do not want the value echoed.' ), '<code>get_trackback_url()</code>' ) ); } if ( $deprecated_echo ) { echo get_trackback_url(); } else { return get_trackback_url(); }}Introduced in 0.71. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/comment-template.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.