4
* talloc is a hierarchical, reference counted memory pool system with
5
* destructors. It is the core memory allocator used in Samba.
7
* @section talloc_download Download
9
* You can download the latest releases of talloc from the
10
* <a href="http://samba.org/ftp/talloc" target="_blank">talloc directory</a>
11
* on the samba public source archive.
13
* @section talloc_bugs Discussion and bug reports
15
* talloc does not currently have its own mailing list or bug tracking system.
16
* For now, please use the
17
* <a href="https://lists.samba.org/mailman/listinfo/samba-technical" target="_blank">samba-technical</a>
18
* mailing list, and the
19
* <a href="http://bugzilla.samba.org/" target="_blank">Samba bugzilla</a>
20
* bug tracking system.
22
* @section talloc_devel Development
23
* You can download the latest code either via git or rsync.
25
* To fetch via git see the following guide:
27
* <a href="http://wiki.samba.org/index.php/Using_Git_for_Samba_Development" target="_blank">Using Git for Samba Development</a>
29
* Once you have cloned the tree switch to the master branch and cd into the
30
* lib/tevent directory.
32
* To fetch via rsync use this command:
34
* rsync -Pavz samba.org::ftp/unpacked/standalone_projects/lib/talloc .
36
* @section talloc_preample Preamble
38
* talloc is a hierarchical, reference counted memory pool system with
41
* Perhaps the biggest difference from other memory pool systems is that there
42
* is no distinction between a "talloc context" and a "talloc pointer". Any
43
* pointer returned from talloc() is itself a valid talloc context. This means
47
* struct foo *X = talloc(mem_ctx, struct foo);
48
* X->name = talloc_strdup(X, "foo");
51
* The pointer X->name would be a "child" of the talloc context "X" which is
52
* itself a child of mem_ctx. So if you do talloc_free(mem_ctx) then it is all
53
* destroyed, whereas if you do talloc_free(X) then just X and X->name are
54
* destroyed, and if you do talloc_free(X->name) then just the name element of
57
* If you think about this, then what this effectively gives you is an n-ary
58
* tree, where you can free any part of the tree with talloc_free().
60
* If you find this confusing, then run the testsuite to watch talloc in
61
* action. You may also like to add your own tests to testsuite.c to clarify
62
* how some particular situation is handled.
64
* @section talloc_performance Performance
66
* All the additional features of talloc() over malloc() do come at a price. We
67
* have a simple performance test in Samba4 that measures talloc() versus
68
* malloc() performance, and it seems that talloc() is about 4% slower than
69
* malloc() on my x86 Debian Linux box. For Samba, the great reduction in code
70
* complexity that we get by using talloc makes this worthwhile, especially as
71
* the total overhead of talloc/malloc in Samba is already quite small.
73
* @section talloc_named Named blocks
75
* Every talloc chunk has a name that can be used as a dynamic type-checking
76
* system. If for some reason like a callback function you had to cast a
77
* "struct foo *" to a "void *" variable, later you can safely reassign the
78
* "void *" pointer to a "struct foo *" by using the talloc_get_type() or
79
* talloc_get_type_abort() macros.
82
* struct foo *X = talloc_get_type_abort(ptr, struct foo);
85
* This will abort if "ptr" does not contain a pointer that has been created
86
* with talloc(mem_ctx, struct foo).
88
* @section talloc_threading Multi-threading
90
* talloc itself does not deal with threads. It is thread-safe (assuming the
91
* underlying "malloc" is), as long as each thread uses different memory
94
* If two threads uses the same context then they need to synchronize in order
95
* to be safe. In particular:
97
* - when using talloc_enable_leak_report(), giving directly NULL as a parent
98
* context implicitly refers to a hidden "null context" global variable, so
99
* this should not be used in a multi-threaded environment without proper
101
* - the context returned by talloc_autofree_context() is also global so
102
* shouldn't be used by several threads simultaneously without