(old?) Projectiles warping when they die deal damage twice

[Turret49]

I don't know how long this bug's been around, found it in 3.3.1 and it's still there in 3.3.2. Even my old 2.4.0 version of GZDoom seems to have this bug!
When a projectile warps on the same tic it dies from hitting something, actors it collides with at its warp destination tend to also get hurt, meaning a projectile can hit (at least?) two different actors or the same actor twice. Notably even when the WARPF_NOCHECKPOSITION flag is set this still happens.

Attached is a .wad with a test pistol that fires a projectile with this DECORATE code:

Code: Select all

actor BuggedProjectile : DoomImpBall
{
  Damage (10)
  States
  {
  XDeath:
	//TNT1 A 1 // bug doesn't occur if there's a delay
	TNT1 A 0 A_Warp(AAPTR_Default,10,10,10,0,WARPF_NOCHECKPOSITION)
  goto Super::Death
  }
}

You can quickly get to the test pistol by inputting IDFA and pressing 2. Note that the Damage (10) projectile often kills the zombies in Doom 2's MAP01 in one shot, and imps three.

[Graf Zahl]

A clear case of "Don't do that!" If you want to have special actions in a projectile's or monster's death state you have to add a one-tic delay. Otherwise the code runs right at the time the actor dies which can have unforeseeable side effects.

[Turret49]

Alright, I couldn't find anything about this from searching, thanks for clarifying. It's just something that happens as a quirk of the death code and should be worked around.