Debugging memory leaks

[Steven D'Aprano]

On Fri, 14 Jun 2013 22:57:24 +0000, Giorgos Tzampanakis wrote:

> On 2013-06-14, Steven D'Aprano wrote:
> 
>> On Thu, 13 Jun 2013 20:15:42 +0000, Giorgos Tzampanakis wrote:
>>
>>>> Therefore: if the leak seems to be small, it may be much more
>>>> advicable to restart your process periodically (during times where a
>>>> restart does not hurt much) rather than try to find (and fix) the
>>>> leaks. Only when the leak is large enough that it would force you to
>>>> too frequent restarts, a deeper analysis may be advicable (large
>>>> leaks are easier to locate as well).
>>> 
>>> 
>>> Am I the only one who thinks this is terrible advice?
>>
>>
>> Sub-optimal, maybe, but terrible? Not even close. Terrible advice would
>> be "open up all the ports on your firewall, that will fix it!"
>>
>> If it takes, say, 200 person-hours to track down this memory leak, and
>> another 200 person-hours to fix it, that's an awful large expense. In
>> that case, it would surely be better to live with the inconvenience and
>> mess of having a nightly/weekly/monthly reboot. On the other hand,
>> maybe it will only take 1 hour to find, and fix, the leak. Who knows?
> 
> But having a memory leak in the first place is an indication that
> something is very wrong with your program. Either you're keeping
> references that you didn't mean to be keeping (which indicates that
> there can be larger side-effects than just wasted memory) or a linked C
> library is leaking memory, which is bad for reasons which I won't cover
> here since they are self-evident.

You mean a bug in your code is a sign that there is a bug in your code? 
Who would have imagined! *wink*

Of course you are right that a memory leak is a bug. And like all bugs, 
ideally you will want to fix it. But sometimes bugs are too difficult to 
fix, and the inconvenience of restarting the app too minor to care. For 
many applications, "restart once a month" is no big deal, especially 
compared to "spend three months trying to track down this one bug, 
instead of doing work that will actually pay the bills".

I'm not suggesting that living with a memory leak is *in and of itself* a 
good thing, only that sometimes there are higher priorities.


-- 
Steven