Server crash on player.teleport?

[Velocity-plus]

Description

• Game: Counter-Strike: Global Offensive
• OS: Linux

Following code crashes server:

from listeners import OnPlayerRunCommand
from mathlib import Vector


@OnPlayerRunCommand
def on_player_run_command(player, user_cmd):
    player.teleport(velocity=Vector(100,100,100)) # Triggers crash

Original Issue:

from entities.entity import Entity
from entities.hooks import EntityCondition, EntityPreHook
from memory import make_object
from messages import SayText2
from players.entity import Player

TARGET_CLASSNAME = 'flashbang_projectile'

@EntityPreHook(
    EntityCondition.equals_entity_classname(TARGET_CLASSNAME),
    "start_touch")
def pre_start_touch(args):
    entity = make_object(Entity, args[0])

    if entity.classname != TARGET_CLASSNAME:
        return
    other = make_object(Entity, args[1])
    if not other.is_player():
        return

    player = make_object(Player, args[1])
    player.teleport(velocity=Vector(100,100,100)) # Triggers crash

[jordanbriere]

Dynamically calling a function within a hook can have undefined behaviors. Try to execute the call on the next frame:

from listeners import OnPlayerRunCommand
from listeners.tick import Delay

@OnPlayerRunCommand
def on_player_run_command(player, user_cmd):
    Delay(0, player.teleport, velocity=Vector(100,100,100))

Also, if you only want to push the player, you could always use Player.base_velocity which applies the given Vector instance to the current velocity of the player.

[KirillMysnik]

Originally reported for start_touch EntityPreHook: http://forums.sourcepython.com/viewtopic.php?p=9063#p9063
Probably related: http://forums.sourcepython.com/viewtopic.php?f=10&t=1158

I wonder when the crash happens in this case.
I've had issues with teleport, but all crashes seemed to happen AFTER the function was successfully called. I mean, inserting a print after teleport, for example, resulted in a successful print and then crashed. The function was called from inside of OnEntityOutput listener. So I guess it crashed when the hooked function was returning control.

Oh, I have experienced this on Windows. While the issue at the second link only happened on Linux, and call to the function itself was crashing the server.

[Ayuto]

@Velocity-plus I guess you are testing on Linux. Is that right?

[Velocity-plus]

Yes I currently am, and I have updated both posts now.

[KirillMysnik]

@invincibleqc Since we're on it, what kind of "undefined behaviors" could this lead to? I've had some weird crashes in my plugin, but was unable to consistently reproduce the crash - it seemed rather random. Do random crashes fall under "undefined behaviour" definition?

Also, I think it's good to clarify somewhere that a "hook" and "dynamically calling a function" might be things not that obvious. For example, PreEvent is based on hooks, OnEntityOutput listener is also based on them. On the other side, Player.view_angle property is based on teleport function. So the issue applies to all of them, too. But these are masked.
Combine this fact with "undefined behavior" and you have a real good case of random, untraceble crash in your plugin.
I believe there should be a note in the docs, like "this feature is hook-based" or "this feature uses function dynamically called".

[Ayuto]

You are supposed to be able to call a function dynamically within a hook, so this is something we definitely need to fix. And if we have fixed it, there is no need to mention that anywhere.

I really need some time to figure out what's wrong, but unfortunately my time is currently very limited.

[njanke96]

I also have this issue. It occurs when calling within an OnEntityOutput listener for the OnStartTouch output. Alternatively, setting player.origin and player.velocity works fine.

EDIT: Oops I lied. That doesn't work either.

[Ayuto]

OnEntityOutput uses a hook internally. Try the suggested workaround (delaying the call).