Arch-Vile fire spawned at the wrong location
From DoomWiki.org
Due to a bug in the Doom engine, the fire from the arch-vile's attack can be spawned at the wrong location. When the fog is initially spawned, the following code is used, which contains a blatant programming error:
//
// A_VileTarget
// Spawn the hellfire
//
void A_VileTarget (mobj_t* actor)
{
mobj_t* fog;
if (!actor->target)
return;
A_FaceTarget (actor);
fog = P_SpawnMobj (actor->target->x,
actor->target->x,
actor->target->z, MT_FIRE);
actor->tracer = fog;
fog->target = actor;
fog->tracer = actor->target;
A_Fire (fog);
}
On the line in bold, the actor's target's x coordinate is used again where the code should instead use the target's y coordinate. This causes the initial position of the fire to be shifted on the x-y plane relative to the target of the arch-vile's attack. Should the target become hidden from the arch-vile's line of sight before the fire's position is updated, the fire will remain in this incorrect position until it dissipates completely.
