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circular references (circular references are allowed, they just need
to be handled carefully inside talloc)
- mark talloc_reference() pointers nicely in the --leak-report-full
code, so you see what has a reference to what in a useful manner
void *talloc_reference(const void *context, const void *ptr);
this function makes a secondary reference to ptr, and hangs it off the
given context. This greatly simplifies some of the current reference
counting code in the samr server and I suspect it will be widely used
in other places too.
the way you use it is like this:
domain_state->connect_state = talloc_reference(domain_state, connect_state);
that makes the element connect_state of domain_state a secondary
reference to connect_state. The connect_state structure will then only
be freed when both domain_state and the original connect_state go
away, allowing you to free them independently and in any order.
you could do this alrady using a talloc destructor, and that is what
the samr server did previously, but that meant this construct was
being reinvented in several places. So this convenience function sets
up the destructor for you, giving a much more convenient and less
error prone API.
a const pointer really means that "the data pointed to by this pointer
won't change", and that is certainly true of talloc(). The fact that
some behind-the-scenes meta-data can change doesn't matter from the
point of view of const.
this fixes a number of const warnings caused by const data structures
being passed as talloc contexts. That will no longer generate a
warning.
also changed the talloc leak reporting option from --leak-check to
--leak-report, as all it does is generate a report on exit. A new
--leak-report-full option has been added that shows the complete tree
of memory allocations, which is is quite useful in tracking things down.
NOTE: I find it quite useful to insert talloc_report_full(ptr, stderr)
calls at strategic points in the code while debugging memory
allocation problems, particularly before freeing a major context (such
as the connection context). This allows you to see if that context has
been accumulating too much data, such as per-request data, which
should have been freed when the request finished.
taking a context (so when you pass a NULL pointer you end up with
memory in a top level context). Fixed it by changing the API to take a
context. The context is only used if the pointer you are reallocing is
NULL.
to get auto-naming of pointers very cheaply.
- fixed a couple of memory leaks found with the new tricks
A typical exit report for smbd is now:
talloc report on 'null_context' (total 811 bytes in 54 blocks)
auth/auth_sam.c:334 contains 20 bytes in 1 blocks
struct auth_serversupplied_info contains 498 bytes in 33 blocks
UNNAMED contains 8 bytes in 1 blocks
lib/data_blob.c:40 contains 16 bytes in 1 blocks
iconv(CP850,UTF8) contains 61 bytes in 4 blocks
iconv(UTF8,CP850) contains 61 bytes in 4 blocks
iconv(UTF8,UTF-16LE) contains 67 bytes in 4 blocks
iconv(UTF-16LE,UTF8) contains 67 bytes in 4 blocks
UNNAMED contains 13 bytes in 1 blocks
which is much better than before
auto-derived from the type you are allocating. This is done with
basically zero overhead by relying on the stringify operator in cpp
producing string constants.
the result is that --leak-check nicely names all pointers that come
from talloc_p()
and can't properly handle leaks of doubly linked lists which we use a
lot (as the memory is always reachable). Even with --show-reachable
its hard to track leaks down sometimes.
I realised that talloc does have the necessary information to track
these, and by using the cascading property of the new talloc it can
report on leaks in a much more succinct fashion than valgrind can.
I have added a new samba option --leak-check that applies to all Samba
tools. When enabled it prints a leak report summarising all top level
contexts that are present when the program exits. A typical report
looks like this:
talloc report on 'null_context' (total 1071 bytes in 52 blocks)
iconv(CP850,UTF8) contains 43 bytes in 3 blocks
UNNAMED contains 24 bytes in 1 blocks
UNNAMED contains 24 bytes in 1 blocks
dcesrv_init contains 604 bytes in 26 blocks
server_service contains 120 bytes in 6 blocks
UNNAMED contains 24 bytes in 1 blocks
UNNAMED contains 24 bytes in 1 blocks
server_service contains 104 bytes in 4 blocks
server_context contains 12 bytes in 2 blocks
iconv(UTF8,UTF-16LE) contains 46 bytes in 3 blocks
iconv(UTF-16LE,UTF8) contains 46 bytes in 3 blocks
the numbers are recursive summaries for all the memory hanging off each context.
this option is not thread safe when used, but the code is thread safe
if the option is not given, so I don't think thats a problem.
this means you can do:
talloc_set_destructor(ptr, my_destructor);
and your destructor will be called with the pointer as an argument
when the pointer is about to be freed. The destructor can refuse the
free by returning -1.
You can also increase the reference count on a pointer like this:
talloc_increase_ref_count(ptr);
and a talloc_free() will just reduce the reference count, only
actually freeing the memory when the count reaches zero.
This version does the following:
1) talloc_free(), talloc_realloc() and talloc_steal() lose their
(redundent) first arguments
2) you can use _any_ talloc pointer as a talloc context to allocate
more memory. This allows you to create complex data structures
where the top level structure is the logical parent of the next
level down, and those are the parents of the level below
that. Then destroy either the lot with a single talloc_free() or
destroy any sub-part with a talloc_free() of that part
3) you can name any pointer. Use talloc_named() which is just like
talloc() but takes the printf style name argument as well as the
parent context and the size.
The whole thing ends up being a very simple piece of code, although
some of the pointer walking gets hairy.
So far, I'm just using the new talloc() like the old one. The next
step is to actually take advantage of the new interface
properly. Expect some new commits soon that simplify some common
coding styles in samba4 by using the new talloc().
talloc_free() O(1) in preparation. This also halves the number of
malloc() calls and increases our internal consistency checking,
without breaking valgrind testing.
implements the epm_Lookup() call, I'll add the other important calls
soon. I was rather pleased to find that epm_Lookup() worked first
time, which is particularly surprising given its complexity.
This required quite a bit of new infrastructure:
* a generic way of handling dcerpc policy handles in the rpc server
* added type checked varients of talloc. These are much less error
prone. I'd like to move to using these for nearly all uses of
talloc.
* added more dcerpc fault handling code, and translation from
NTSTATUS to a dcerpc fault code
* added data_blob_talloc_zero() for allocating an initially zero
blob
* added a endpoint enumeration hook in the dcerpc endpoint server
operations
