Collectible Card Game Headquarters

Describe the Bug:
Giant Turtle can attack even though it attacked your last turn.At least AI can do it.Besides no effect card is attached to it after it attacks.

Which card did behave improperly?
Giant Turtle

Which update are you using? (date, name)Which type? (duel, gauntlet, sealed deck)
Manalink 2016/08/27: Eldritch Moon v2, sealed

What exactly should be the correct behavior/interaction?
Giant Turtle
Rulings
4/10/2004 It only cares if it attacked on _your_ last turn, and not your opponent’s. This makes a difference if you take control of the Turtle during your opponent’s turn after it attacks. You can use it on your turn because it began your turn on the battlefield and because you did not attack with it last turn.
Are any other cards possibly affected by this bug?
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Fix this in commit 4815d35.

This method isn't resilient to copy effects. That is, if something makes the Giant Turtle a copy of another card on the turn it attacks, the turtle's info_slot won't be updated. (...usually. Both that info_slot update and the removal of until-end-of-turn effects happen during EVENT_CLEANUP, so it depends on which card gets the event first. EVENT_CLEANUP isn't sent in timestamp order in Manalink, but in card index order; those end up being usually the same for the first 150 cards created for each player, but isn't predictable afterwards. (Which is why the the for-loops in Manalink that decrement card index only hide bugs and never fix them, but I was already digressing before this digression.)) The only robust way to handle cards like this that look back in time is to record the information for all cards, not just ones that happen to be a Giant Turtle at the time.

Is there a card template I can compare so I can try to fix this?

Not in Manalink that I'm aware of. Similar cards - Goblin Rock Sled and Tangle Kelp - do it the same way.

For the creature-based ones, the same bug can be exercised more practically with something like Act of Treason the turn after it attacks, since you're only recording whether or not it attacked on its then-current controller's turn, not who the controller was.

For Tangle Kelp, the situation's much, much worse - cast it on your opponent's creature and it'll always untap on the next turn, whether it attacked or not; attach it to another creature with Enchantment Alteration or similar and it'll prevent the new creature from untapping or not based on whether whatever it was last attached to during that creature's controller's end step had attacked.