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 | | From: | Ole Andre Karlson | | Subject: | MallocDebug/ObjectAlloc | | Date: | Wed, 29 Dec 2004 15:17:50 +0100 |
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 | Hi,
MallocDebug and ObjectAlloc are giving me conflicting reports :(
According to MallocDebug my application doesn't leak while ObjectAlloc
tells me I'm loosing a bunch of GeneralBlocks once every minute or so..
Who should I trust?
thanks
Ole Andre Karlson
oleaka@ifi.uio.no
http://heim.ifi.uio.no/~oleaka
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| | From: | Michael Ash | | Subject: | Re: MallocDebug/ObjectAlloc | | Date: | Wed, 29 Dec 2004 16:41:43 -0600 |
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| Ole Andre Karlson wrote:
> Hi,
>
> MallocDebug and ObjectAlloc are giving me conflicting reports :(
> According to MallocDebug my application doesn't leak while ObjectAlloc
> tells me I'm loosing a bunch of GeneralBlocks once every minute or so..
>
> Who should I trust?
MallocDebug and ObjectAlloc don't do the same kind of thing.
MallocDebug checks for unreachable objects. This is an object that has no
possible reference to it anywhere in the application. It is basically a
garbage collector without the collector part.
ObjectAlloc works by having you perform an action that shouldn't increase
the total number of objects allocated, and then seeing if the number of
objects allocated actually goes up or not.
It's entirely possible for ObjectAlloc to report a "leak" that isn't
really a leak. If you're building a list of objects and adding to that
list, ObjectAlloc will show a "leak" because the number of objects isn't
constant, but it's not a real leak.
It's also possible to write a leak that MallocDebug won't find, because
you still have a reference to the object. For example, if you have a
global mutable array and you add an object to that array, but never use
the object again or remove it from the array, this is a legitimate memory
leak, but MallocDebug won't find it because it's still referenced.
As far as who you should trust, I personally believe that I get the best
results using 'leaks' from the command line. In theory it should show
pretty much the same results as MallocDebug, but it seems to work a lot
better.
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