wp-includes/feed.php:279Displays the feed GUID for the current comment.
$comment_idint|WP_Commentoptionalnullfunction comment_guid( $comment_id = null ) { echo esc_url( get_comment_guid( $comment_id ) );}Introduced in 2.5.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/feed.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.