ent->**parent** was nullptr.

[JaceSolarisVIII]

Unhandled exception thrown: read access violation.
ent->**parent** was nullptr.

 

I could use some help. I have been trying to get my deletion function to work correctly, but no matter what I seem to do it always gives me a "was nullptr" error.  Everywhere I have looked for information about nullptr has not really given an explanation that I actually understand. My understanding is that a "was nullptr" error is given when you try to dereference a pointer/node, but I could never find a way to handle the issue that made sense to me. Any help is really appreciated. My code is:

void Weapon_HookFree(gentity_t *ent)
{
	ent->parent->client->fireHeld = qfalse;
	ent->parent->client->hookhasbeenfired = qfalse;
	ent->parent->client->hook = NULL;
	ent->parent->client->ps.pm_flags &= ~PMF_GRAPPLE_PULL;
	G_FreeEntity(ent);
}

This is for singleplayer only and does not show this error in mp.

[Raz0r]

No way to tell without seeing all of your related code changes (specifically where Weapon_HookFree is being called from).

There's an assumption that a hook belongs to another entity (player), but that doesn't seem to be true; ent->parent should have been set long before Weapon_HookFree was called (e.g. upon hook creation) but wasn't, or it was cleared at some other point in time (or you're calling Weapon_HookFree on a non-hook entity).

 

A more general solution: learn to debug, get a backtrace, etc.

[JaceSolarisVIII]

No way to tell without seeing all of your related code changes (specifically where Weapon_HookFree is being called from).

There's an assumption that a hook belongs to another entity (player), but that doesn't seem to be true; ent->parent should have been set long before Weapon_HookFree was called (e.g. upon hook creation) but wasn't, or it was cleared at some other point in time (or you're calling Weapon_HookFree on a non-hook entity).

 

A more general solution: learn to debug, get a backtrace, etc.

Thank you for responding to this post, The Weapon_HookFree is being called in g_active.cpp in void ClientThink_real( gentity_t *ent, usercmd_t *ucmd ).

 (ent->client->ps.weapon == WP_MELEE)
	{
		if (ucmd->buttons & BUTTON_GRAPPLE &&
			ent->client->ps.pm_type != PM_DEAD &&
			!ent->client->hookhasbeenfired &&
			!(PM_SaberInAttack(ent->client->ps.saberMove)))
		{
			if (ent->client && ent->client->hookDebounceTime > level.time)
			{
				if (client->hook)
				{
					Weapon_HookFree(client->hook);
				}
			}
			else
			{
				Weapon_GrapplingHook_Fire(ent);
				ent->client->hookhasbeenfired = qtrue;
				NPC_SetAnim(ent, SETANIM_BOTH, BOTH_PULL_IMPALE_STAB, SETANIM_FLAG_OVERRIDE | SETANIM_FLAG_HOLD, 0);
				G_SoundOnEnt(ent, CHAN_ITEM, "sound/weapons/grapple/hookfire.wav");
				ent->client->hookDebounceTime = level.time + 0;
			}
		}
		else if (client->hook && (client->fireHeld == qfalse ||
			!(ucmd->buttons & BUTTON_GRAPPLE) ||
			(ucmd->buttons & BUTTON_USE) ||
			(ent->client->ps.pm_type == PM_DEAD)))
		{
			Weapon_HookFree(client->hook);
		}
	}
	else
	{
		if (client->hook && (client->fireHeld == qfalse ||
			!(ucmd->buttons & BUTTON_GRAPPLE) ||
			(ucmd->buttons & BUTTON_USE) ||
			(ucmd->buttons & BUTTON_BLOCK) ||
			(ent->client->ps.pm_type == PM_DEAD)))
		{
			Weapon_HookFree(client->hook);
		}

		if (!(ent->client->ps.eFlags & EF_FIRING))
		{
			client->fireHeld = qfalse;
		}
	}

g_client.cpp in void ClientDisconnect( int clientNum ).

void ClientDisconnect( int clientNum )
{
	gentity_t	*ent;

	ent = g_entities + clientNum;
	if ( !ent->client )
	{
		return;
	}

	gi.unlinkentity (ent);
	ent->s.modelindex = 0;
	ent->inuse = qfalse;
	ClearInUse(ent);
	ent->classname = "disconnected";
	ent->client->pers.connected = CON_DISCONNECTED;
	ent->client->ps.persistant[PERS_TEAM] = TEAM_FREE;
	if (ent->client->hook)
	{ // free it!
		Weapon_HookFree(ent->client->hook);
	}

	gi.SetConfigstring( CS_PLAYERS + clientNum, "");

	IIcarusInterface::GetIcarus()->DeleteIcarusID(ent->m_iIcarusID);

}

g_combat.cpp in void player_die.

	if (self->client->hook)
	{ // free it!
		Weapon_HookFree(self->client->hook);
	}

and finally g_missile.cpp.

#define MISSILE_PRESTEP_TIME 50
/*
=================
fire_grapple
=================
*/
gentity_t *fire_grapple(gentity_t *self, vec3_t start, vec3_t dir)
{
	gentity_t	*hook;

	VectorNormalize(dir);

	hook = G_Spawn();
	hook->classname = "hook";
	hook->nextthink = level.time + 10000;
	hook->think = Weapon_HookFree;
	hook->s.eType = ET_MISSILE;
	hook->svFlags = SVF_USE_CURRENT_ORIGIN;
	hook->s.weapon = WP_MELEE;
	hook->ownerNum = self->s.number;
	hook->methodOfDeath = MOD_ELECTROCUTE;
	hook->clipmask = MASK_SHOT;
	hook->parent = self;
	hook->target_ent = NULL;
	hook->s.pos.trType = TR_LINEAR;
	hook->s.pos.trTime = level.time - MISSILE_PRESTEP_TIME;
	hook->s.otherEntityNum = self->s.number;
	VectorCopy(start, hook->s.pos.trBase);
	VectorScale(dir, 900, hook->s.pos.trDelta);
	SnapVector(hook->s.pos.trDelta);
	VectorCopy(start, hook->currentOrigin);
	self->client->hook = hook;

	return hook;
}

These are the only places where Weapon_HookFree is being called?

​​​

[Raz0r]

That all looks fine.

 

The only thing I can theorise is if Weapon_HookFree is being called by ent->think() at some point after either:

- hook->parent is being set to null

- ent->client->hook is being set to a non-hook entity

 

Backtrace/debugging is the way to go.