Mailing Lists: Apple Mailing Lists
Image of Mac OS face in stamp
 
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: how to set NavDialogCreationOptions strings

On Jul 29, 2004, at 6:17 PM, Frederick Cheung wrote:

> On 30 Jul 2004, at 00:37, Kurt Bigler wrote:
>
>>> gs just replace
>>> the ones that are there with your own CFStringRefs.
>>>
>>>> First I thought these strings must be mutable else it would be
>>>> unsafe to
>>>> modify the strings in NavDialogCreationOptions. But maybe I am
>>>> expected to
>>>> dispose the old strings and create new ones to assign to the fields?
>>>> Otherwise--I could not find an API to reassign the value of a
>>>> mutable string.
>>>> Doing a replace operation seems like overkill.
>>>>
>>> They are not mutable (if they were they would be
>>> CFMutableStringRefs).
>>> I wouldn't release the strings either (you didn't create them so you
>>> shouldn't release them). Just assign your own CFStringRefs into the
>>> fields and ignore the default values.
>>
>> Why isn't that a memory leak?
>>
> Well it's not a memory leak if you don't own those strings.

It could, potentially, be a memory leak, but there's no way for you to
know.

I strongly suspect, however, that it is not.

At the very least, the operating system is probably expecting to use
the same strings every time you create default dialog options. If you
were to free those strings out from under the Navigation Services
framework, that would be a Bad Thing

If I had to guess at how Navigation services is implemented, however, I
would say that you couldn't really "free" those strings even if you
tried. The operating system is probably creating a CFString from a
static string somewhere using the same technology that sits behind the
CFSTR macro. With such objects you can pretty much think of the string
as being created at compile-time and stored in the program's global
data.

As I understand, these strings can actually participate in
retain-release semantics. Since the memory can't actually be freed,
however, releasing them enough that they should be freed is actually
an unsupported operation with undefined behavior (at least according to
engineers at Apple).

The thing to keep in mind here, however, is that you didn't allocate
those strings so you are not responsible for releasing them. If it is
a memory leak... it's the OSes fault and not yours.

--
Macintosh Software Engineering Consulting Services
Visit my resume at <http://homepage.mac.com/easco/RSTResume.html>

[demime 0.98b removed an attachment of type application/pkcs7-signature which had a name of smime.p7s]
_______________________________________________
carbon-development mailing list | email@hidden
Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/carbon-development
Do not post admin requests to the list. They will be ignored.

References: 
 >Re: how to set NavDialogCreationOptions strings (From: Kurt Bigler <email@hidden>)
 >Re: how to set NavDialogCreationOptions strings (From: Frederick Cheung <email@hidden>)



Visit the Apple Store online or at retail locations.
1-800-MY-APPLE

Contact Apple | Terms of Use | Privacy Policy

Copyright © 2007 Apple Inc. All rights reserved.