Summary

When the Overlord tank has a Gatling Cannon upgrade and the player issues a force-attack on empty terrain (no units, no buildings — just ground), the Gatling Cannon disappears from the Overlord. Because the upgrade slot is consumed, the Gatling cannot be re-built.

This does not affect:

• Normal attacks against actual targets (units, buildings) — Gatling fires correctly
• Propaganda Tower upgrade — never disappears regardless of force-attack
• BattleBunker upgrade — unaffected

Steps to Reproduce

1. Build an Overlord tank (China faction)
2. Apply the Gatling Cannon upgrade
3. Select the Overlord
4. Force-attack (A + click) on an empty area of terrain with no targets
5. Gatling Cannon disappears

Root Cause Analysis

The Gatling Cannon's AI enters the following state chain when force-attacking empty terrain:

aiAttackPosition
  → AI_ATTACK_POSITION (AIAttackState)
    → AttackStateMachine::AIM_AT_TARGET
      → outOfWeaponRange → CHASE_TARGET
        → ContinueState (KINDOF_PORTABLE_STRUCTURE + KINDOF_CAN_ATTACK special case)
          → EXIT_MACHINE_WITH_FAILURE
    → STATE_FAILURE → AI_EXIT_INSTANTLY
      → AIExitInstantlyState::onEnter()
        → goalExitInterface->exitObjectViaDoor(obj, DOOR_1)  ← Gatling ejected here

The key issue is in AttackStateMachine constructor (AIStates.cpp): when the attacker is both KINDOF_PORTABLE_STRUCTURE and KINDOF_CAN_ATTACK, CHASE_TARGET is a ContinueState that always fails — this is intentional (portables can't move), but it causes AI_EXIT_INSTANTLY to be triggered.

The Propaganda Tower never hits this path because it has no attack weapons and never enters attack states — its healing works via PropagandaTowerBehavior area scan.

Attempted Fixes

Two guards were added to OverlordContain (commits 93de21fe6, 689b38e78):

1. isSpecificRiderFreeToExit() — blocks AIExitState (normal exit via reserveDoorForExit). Works.
2. exitObjectViaDoor() — meant to block AIExitInstantlyState which calls exitObjectViaDoor(DOOR_1) directly, bypassing reserveDoorForExit. Did not resolve the issue.

The exact bypass mechanism when exitObjectViaDoor override is in place is not yet identified. Possible unexplored paths:

• removeFromContain() called directly from a different code path
• getContainExitInterface() returning a different ExitInterface in this context
• A different trigger (not AI_EXIT_INSTANTLY) causing the removal

Affected Files

• GeneralsMD/Code/GameEngine/Source/GameLogic/Object/Contain/OverlordContain.cpp
• GeneralsMD/Code/GameEngine/Source/GameLogic/AI/AIStates.cpp (AttackStateMachine, AIExitInstantlyState)

Workaround

None currently. Avoid force-attacking empty terrain with an Overlord that has the Gatling Cannon upgrade.

Platform

macOS (POSIX port). Behavior on original Windows/VC6 build is unknown — the locomotor-based DISABLED_HELD mechanism may have prevented the issue naturally on that platform.