wp-includes/deprecated.php:3319Callback formerly fired on the save_post hook. No longer needed.
function _save_post_hook() {}Introduced in 2.3.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/deprecated.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.