[sldev] [VIEWER] Daring construct? (is this safe?)

[Nicholaz Beresford]

A first quick (semi random) check brings up

W:\sl1_18_3_5\linden\indra\newview\llselectmgr.cpp(5863):
		erase(mCurrentNode++);

where mCurrentNode is an interator on a std::list.


Nick
---
Second Life from the inside out:
http://nicholaz-beresford.blogspot.com/


Q Linden wrote:
> Yes, this is safe. The iterator post-increment returns a temporary copy 
> of the previous value, which is used for the erase (and invalidated). 
> The gi iterator is still valid in a map.
> 
> If mGroups had been a vector or other non-hashed container instead of a 
> map, erasing an item invalidates ALL iterators and the code would be 
> unsafe.
> 
>    Q
> 
> Nicholaz Beresford wrote:
>>
>> Seen in llgroupmgr.cpp at 1330
>>
>> mGroups is a std::map.
>>
>> Question is if the mGroups.erase(gi++); is safe or depends on
>> order of evaluation and/or possibly accesses freed memory
>> (doing the increment after the erase)?
>>
>> (I'm seeing this in a lot of places ... grep erase\(.*++\);   ).
>>
>>
>>
>> // get rid of groups that aren't observed
>> for (group_iter gi = mGroups.begin(); gi != mGroups.end() && 
>> mGroups.size() > MAX_CACHED_GROUPS / 2; )
>> {
>>     observer_iter oi = mObservers.find(gi->first);
>>     if (oi == mObservers.end())
>>     {
>>         // not observed
>>         LLGroupMgrGroupData* group_datap = gi->second;
>>         delete group_datap;
>>         mGroups.erase(gi++);
>>     }
>>     else
>>     {
>>         ++gi;
>>     }
>> }
>>
>>
>