1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
|
/**
* @mainpage
*
* talloc is a hierarchical, reference counted memory pool system with
* destructors. It is the core memory allocator used in Samba.
*
* @section talloc_download Download
*
* You can download the latest releases of talloc from the
* <a href="http://samba.org/ftp/talloc" target="_blank">talloc directory</a>
* on the samba public source archive.
*
* @section main-tutorial Tutorial
*
* You should start by reading @subpage libtalloc_tutorial, then reading the documentation of
* the interesting functions as you go.
* @section talloc_bugs Discussion and bug reports
*
* talloc does not currently have its own mailing list or bug tracking system.
* For now, please use the
* <a href="https://lists.samba.org/mailman/listinfo/samba-technical" target="_blank">samba-technical</a>
* mailing list, and the
* <a href="http://bugzilla.samba.org/" target="_blank">Samba bugzilla</a>
* bug tracking system.
*
* @section talloc_devel Development
* You can download the latest code either via git or rsync.
*
* To fetch via git see the following guide:
*
* <a href="http://wiki.samba.org/index.php/Using_Git_for_Samba_Development" target="_blank">Using Git for Samba Development</a>
*
* Once you have cloned the tree switch to the master branch and cd into the
* lib/tevent directory.
*
* To fetch via rsync use this command:
*
* rsync -Pavz samba.org::ftp/unpacked/standalone_projects/lib/talloc .
*
* @section talloc_preample Preamble
*
* talloc is a hierarchical, reference counted memory pool system with
* destructors.
*
* Perhaps the biggest difference from other memory pool systems is that there
* is no distinction between a "talloc context" and a "talloc pointer". Any
* pointer returned from talloc() is itself a valid talloc context. This means
* you can do this:
*
* @code
* struct foo *X = talloc(mem_ctx, struct foo);
* X->name = talloc_strdup(X, "foo");
* @endcode
*
* The pointer X->name would be a "child" of the talloc context "X" which is
* itself a child of mem_ctx. So if you do talloc_free(mem_ctx) then it is all
* destroyed, whereas if you do talloc_free(X) then just X and X->name are
* destroyed, and if you do talloc_free(X->name) then just the name element of
* X is destroyed.
*
* If you think about this, then what this effectively gives you is an n-ary
* tree, where you can free any part of the tree with talloc_free().
*
* If you find this confusing, then run the testsuite to watch talloc in
* action. You may also like to add your own tests to testsuite.c to clarify
* how some particular situation is handled.
*
* @section talloc_performance Performance
*
* All the additional features of talloc() over malloc() do come at a price. We
* have a simple performance test in Samba4 that measures talloc() versus
* malloc() performance, and it seems that talloc() is about 4% slower than
* malloc() on my x86 Debian Linux box. For Samba, the great reduction in code
* complexity that we get by using talloc makes this worthwhile, especially as
* the total overhead of talloc/malloc in Samba is already quite small.
*
* @section talloc_named Named blocks
*
* Every talloc chunk has a name that can be used as a dynamic type-checking
* system. If for some reason like a callback function you had to cast a
* "struct foo *" to a "void *" variable, later you can safely reassign the
* "void *" pointer to a "struct foo *" by using the talloc_get_type() or
* talloc_get_type_abort() macros.
*
* @code
* struct foo *X = talloc_get_type_abort(ptr, struct foo);
* @endcode
*
* This will abort if "ptr" does not contain a pointer that has been created
* with talloc(mem_ctx, struct foo).
*
* @section talloc_threading Multi-threading
*
* talloc itself does not deal with threads. It is thread-safe (assuming the
* underlying "malloc" is), as long as each thread uses different memory
* contexts.
*
* If two threads uses the same context then they need to synchronize in order
* to be safe. In particular:
*
* - when using talloc_enable_leak_report(), giving directly NULL as a parent
* context implicitly refers to a hidden "null context" global variable, so
* this should not be used in a multi-threaded environment without proper
* synchronization. In threaded code turn off null tracking using
* talloc_disable_null_tracking().
* - the context returned by talloc_autofree_context() is also global so
* shouldn't be used by several threads simultaneously without
* synchronization.
*
*/
|
