PATCH: Re: talloc -- Eureka*
sam at liddicott.com
Thu Jul 30 06:52:29 MDT 2009
* Stefan (metze) Metzmacher wrote, On 29/07/09 21:11:
> See the top 3 commits here (the others have nothing to do with this
>> The first patch adds talloc_reference_sticky and
> What about adding your sticky code above my new branch?
> And please use 'sticky' instead of slippy in all places:-)
OK... first serious patch attempt attached.
I've used the word non_stick is some places, and slippy in none.
I want to say first that I noticed metzes talloc refactoring in the
master4-talloc-sam branch when I was almost done; and I like it very much.
I've used a macro TALLOC_MAGIC_NO_OWNER in preparation for metzes (your)
refactoring, but not bought in the re-factoring because I don't want to
obscure the changes I'm trying to make here.
I hope the refactoring can be applied on top of this at some point as it
makes talloc much more pleasant to read. [I've been breaking apart
talloc as part of a noweb literate-programming book on talloc in attempt
to unify memory management across systems (think of libgd and php and
swig, linking code together that has their own incompatible ref-count
mechanism). How nice for php to transparently use gnomes ref-counting on
gtk widgets and gd's ref counting on gd objects, and even nicer if this
is based on talloc -- but thats all another story]
I haven't added test cases but it does pass current tests. (Probably all
existing tests would want repeating with a varied mix of sticky
I don't think we need a non-sticky version of talloc_increase_refcount
as it is only used once in samba outside of talloc and it's test suite;
source4/ntvfs/posix/pvfs_wait.c: (req = pwait->req)
which could be easily adjusted as like the precious function in that file.
I also fix a possible bug at the bottom of talloc_unlink where we would
still make the final call to talloc_unreference even if new_parent == NULL.
I also fix a bug in my previous reference destructor where I fail to
properly check the parent of the referenced pointer.
I independantly fixed some things that I now see metze also fixed in
master4-talloc-sam branch, e.g. checking TALLOC_MAGIC_NO_OWNER at top of
metzes talloc refactoring of _talloc_free_children also nice answers
In talloc_free_internal when we free children, would it be simpler to
call talloc_unlink which seems to employ similar strategies? Likewise
Maybe I missed other metze fixes; he seems very sharp eyed.
* I note that talloc_reference_count does distinguish between references
and parents and doesn't count parents as references. I don't know if
this is desirable, or what the current parent===reference philosphy is.
* I note that talloc_realloc() is not allowed on referenced pointers
because of course no track is kept of copies to the original pointer. I
mention this only because it is another function that might fail with
references. (One day we could work around this using indirect pointers
whose parent is the thing being tracked).
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