Re: delete, hash_map

From:

Thomas Maeder <maeder@glue.ch>

Newsgroups:

comp.lang.c++.moderated

Date:

Sat, 5 May 2007 15:21:23 CST

Message-ID:

<m2d51fu6on.fsf@glue.ch>

SimpleCode <DragonXLong@gmail.com> writes:

class COsgCar;
class moving_vechicle;
hash_map<moving_vechicle*, COsgCar*> m_hash;

hash_map<moving_vechicle*, COsgCar*>::iterator iter;

iter = m_hash.find( pMovingVechicle );
if ( iter != m_hash.end() )
{
COsgCar *p = m_hash[pMovingVechicle];
delete p;
}
///////////////////////////////////////
It always run error.

Please elaborate. What kind of error?

I don't know why.

Well, you are leaving a pointer in the map that you are not even
allowed to read (let alone dereference). This can cause all kinds of
trouble in the code you don't show us (technically also in the code
you do show us, but it's not very likely).

Did you mean to also remove the element from the hash_map?

Side note: It seems that your hash_map owns the COsgCar objects that
its elements refer to. If that's the case, consider chaing the
m_hash's type to something like

hash_map<moving_vechicle*, boost::shared_ptr<COsgCar> > m_hash;

and you won't have to explictly delete the COsgCar objects after
removing the hash_map elements that refer to them.

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