summaryrefslogtreecommitdiff
path: root/lib/talloc/talloc_guide.txt
blob: 18663b370d9dc4d8b9aaeae28ef40655cd4d97c4 (plain)
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
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
Using talloc in Samba4
----------------------

Andrew Tridgell
September 2004

The most current version of this document is available at
   http://samba.org/ftp/unpacked/samba4/source/lib/talloc/talloc_guide.txt

If you are used to the "old" talloc from Samba3 before 3.0.20 then please read
this carefully, as talloc has changed a lot. With 3.0.20 (or 3.0.14?) the
Samba4 talloc has been ported back to Samba3, so this guide applies to both.

The new talloc is a hierarchical, reference counted memory pool system
with destructors. Quite a mouthful really, but not too bad once you
get used to it.

Perhaps the biggest change from Samba3 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:

  struct foo *X = talloc(mem_ctx, struct foo);
  X->name = talloc_strdup(X, "foo");

and 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 I suggest you 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.


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.


talloc API
----------

The following is a complete guide to the talloc API. Read it all at
least twice.

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 ;
- the context returned by talloc_autofree_context() is also global so  
shouldn't be used by several threads simultaneously without  
synchronization.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
(type *)talloc(const void *context, type);

The talloc() macro is the core of the talloc library. It takes a
memory context and a type, and returns a pointer to a new area of
memory of the given type.

The returned pointer is itself a talloc context, so you can use it as
the context argument to more calls to talloc if you wish.

The returned pointer is a "child" of the supplied context. This means
that if you talloc_free() the context then the new child disappears as
well. Alternatively you can free just the child.

The context argument to talloc() can be NULL, in which case a new top
level context is created. 


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_size(const void *context, size_t size);

The function talloc_size() should be used when you don't have a
convenient type to pass to talloc(). Unlike talloc(), it is not type
safe (as it returns a void *), so you are on your own for type checking.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
(typeof(ptr)) talloc_ptrtype(const void *ctx, ptr);

The talloc_ptrtype() macro should be used when you have a pointer and
want to allocate memory to point at with this pointer. When compiling
with gcc >= 3 it is typesafe. Note this is a wrapper of talloc_size()
and talloc_get_name() will return the current location in the source file.
and not the type.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
int talloc_free(void *ptr);

The talloc_free() function frees a piece of talloc memory, and all its
children. You can call talloc_free() on any pointer returned by
talloc().

The return value of talloc_free() indicates success or failure, with 0
returned for success and -1 for failure. The only possible failure
condition is if the pointer had a destructor attached to it and the
destructor returned -1. See talloc_set_destructor() for details on
destructors.

If this pointer has an additional parent when talloc_free() is called
then the memory is not actually released, but instead the most
recently established parent is destroyed. See talloc_reference() for
details on establishing additional parents.

For more control on which parent is removed, see talloc_unlink()

talloc_free() operates recursively on its children.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
int talloc_free_children(void *ptr);

The talloc_free_children() walks along the list of all children of a
talloc context and talloc_free()s only the children, not the context
itself.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_reference(const void *context, const void *ptr);

The talloc_reference() function makes "context" an additional parent
of "ptr".

The return value of talloc_reference() is always the original pointer
"ptr", unless talloc ran out of memory in creating the reference in
which case it will return NULL (each additional reference consumes
around 48 bytes of memory on intel x86 platforms).

If "ptr" is NULL, then the function is a no-op, and simply returns NULL.

After creating a reference you can free it in one of the following
ways:

  - you can talloc_free() any parent of the original pointer. That
    will reduce the number of parents of this pointer by 1, and will
    cause this pointer to be freed if it runs out of parents.

  - you can talloc_free() the pointer itself. That will destroy the
    most recently established parent to the pointer and leave the
    pointer as a child of its current parent.

For more control on which parent to remove, see talloc_unlink()


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
int talloc_unlink(const void *context, const void *ptr);

The talloc_unlink() function removes a specific parent from ptr. The
context passed must either be a context used in talloc_reference()
with this pointer, or must be a direct parent of ptr. 

Note that if the parent has already been removed using talloc_free()
then this function will fail and will return -1.  Likewise, if "ptr"
is NULL, then the function will make no modifications and return -1.

Usually you can just use talloc_free() instead of talloc_unlink(), but
sometimes it is useful to have the additional control on which parent
is removed.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void talloc_set_destructor(const void *ptr, int (*destructor)(void *));

The function talloc_set_destructor() sets the "destructor" for the
pointer "ptr". A destructor is a function that is called when the
memory used by a pointer is about to be released. The destructor
receives the pointer as an argument, and should return 0 for success
and -1 for failure.

The destructor can do anything it wants to, including freeing other
pieces of memory. A common use for destructors is to clean up
operating system resources (such as open file descriptors) contained
in the structure the destructor is placed on.

You can only place one destructor on a pointer. If you need more than
one destructor then you can create a zero-length child of the pointer
and place an additional destructor on that.

To remove a destructor call talloc_set_destructor() with NULL for the
destructor.

If your destructor attempts to talloc_free() the pointer that it is
the destructor for then talloc_free() will return -1 and the free will
be ignored. This would be a pointless operation anyway, as the
destructor is only called when the memory is just about to go away.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
int talloc_increase_ref_count(const void *ptr);

The talloc_increase_ref_count(ptr) function is exactly equivalent to:

  talloc_reference(NULL, ptr);

You can use either syntax, depending on which you think is clearer in
your code.

It returns 0 on success and -1 on failure.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
size_t talloc_reference_count(const void *ptr);

Return the number of references to the pointer.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void talloc_set_name(const void *ptr, const char *fmt, ...);

Each talloc pointer has a "name". The name is used principally for
debugging purposes, although it is also possible to set and get the
name on a pointer in as a way of "marking" pointers in your code.

The main use for names on pointer is for "talloc reports". See
talloc_report() and talloc_report_full() for details. Also see
talloc_enable_leak_report() and talloc_enable_leak_report_full().

The talloc_set_name() function allocates memory as a child of the
pointer. It is logically equivalent to:
  talloc_set_name_const(ptr, talloc_asprintf(ptr, fmt, ...));

Note that multiple calls to talloc_set_name() will allocate more
memory without releasing the name. All of the memory is released when
the ptr is freed using talloc_free().


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void talloc_set_name_const(const void *ptr, const char *name);

The function talloc_set_name_const() is just like talloc_set_name(),
but it takes a string constant, and is much faster. It is extensively
used by the "auto naming" macros, such as talloc_p().

This function does not allocate any memory. It just copies the
supplied pointer into the internal representation of the talloc
ptr. This means you must not pass a name pointer to memory that will
disappear before the ptr is freed with talloc_free().


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_named(const void *context, size_t size, const char *fmt, ...);

The talloc_named() function creates a named talloc pointer. It is
equivalent to:

   ptr = talloc_size(context, size);
   talloc_set_name(ptr, fmt, ....);


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_named_const(const void *context, size_t size, const char *name);

This is equivalent to:

   ptr = talloc_size(context, size);
   talloc_set_name_const(ptr, name);


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
const char *talloc_get_name(const void *ptr);

This returns the current name for the given talloc pointer. See
talloc_set_name() for details.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_init(const char *fmt, ...);

This function creates a zero length named talloc context as a top
level context. It is equivalent to:

  talloc_named(NULL, 0, fmt, ...);


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_new(void *ctx);

This is a utility macro that creates a new memory context hanging
off an exiting context, automatically naming it "talloc_new: __location__"
where __location__ is the source line it is called from. It is
particularly useful for creating a new temporary working context.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
(type *)talloc_realloc(const void *context, void *ptr, type, count);

The talloc_realloc() macro changes the size of a talloc
pointer. The "count" argument is the number of elements of type "type"
that you want the resulting pointer to hold. 

talloc_realloc() has the following equivalences:

  talloc_realloc(context, NULL, type, 1) ==> talloc(context, type);
  talloc_realloc(context, NULL, type, N) ==> talloc_array(context, type, N);
  talloc_realloc(context, ptr, type, 0)  ==> talloc_free(ptr);

The "context" argument is only used if "ptr" is NULL, otherwise it is
ignored.

talloc_realloc() returns the new pointer, or NULL on failure. The call
will fail either due to a lack of memory, or because the pointer has
more than one parent (see talloc_reference()).


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_realloc_size(const void *context, void *ptr, size_t size);

the talloc_realloc_size() function is useful when the type is not 
known so the typesafe talloc_realloc() cannot be used.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_steal(const void *new_ctx, const void *ptr);

The talloc_steal() function changes the parent context of a talloc
pointer. It is typically used when the context that the pointer is
currently a child of is going to be freed and you wish to keep the
memory for a longer time. 

The talloc_steal() function returns the pointer that you pass it. It
does not have any failure modes.

NOTE: It is possible to produce loops in the parent/child relationship
if you are not careful with talloc_steal(). No guarantees are provided
as to your sanity or the safety of your data if you do this.

talloc_steal (new_ctx, NULL) will return NULL with no sideeffects.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
size_t talloc_total_size(const void *ptr);

The talloc_total_size() function returns the total size in bytes used
by this pointer and all child pointers. Mostly useful for debugging.

Passing NULL is allowed, but it will only give a meaningful result if
talloc_enable_leak_report() or talloc_enable_leak_report_full() has
been called.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
size_t talloc_total_blocks(const void *ptr);

The talloc_total_blocks() function returns the total memory block
count used by this pointer and all child pointers. Mostly useful for
debugging.

Passing NULL is allowed, but it will only give a meaningful result if
talloc_enable_leak_report() or talloc_enable_leak_report_full() has
been called.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void talloc_report_depth_cb(const void *ptr, int depth, int max_depth,
			    void (*callback)(const void *ptr,
			    		     int depth, int max_depth,
					     int is_ref,
					     void *priv),
			    void *priv);

This provides a more flexible reports than talloc_report(). It
will recursively call the callback for the entire tree of memory
referenced by the pointer. References in the tree are passed with
is_ref = 1 and the pointer that is referenced.

You can pass NULL for the pointer, in which case a report is
printed for the top level memory context, but only if
talloc_enable_leak_report() or talloc_enable_leak_report_full()
has been called.

The recursion is stopped when depth >= max_depth.
max_depth = -1 means only stop at leaf nodes.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void talloc_report_depth_file(const void *ptr, int depth, int max_depth, FILE *f);

This provides a more flexible reports than talloc_report(). It
will let you specify the depth and max_depth.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void talloc_report(const void *ptr, FILE *f);

The talloc_report() function prints a summary report of all memory
used by ptr. One line of report is printed for each immediate child of
ptr, showing the total memory and number of blocks used by that child.

You can pass NULL for the pointer, in which case a report is printed
for the top level memory context, but only if
talloc_enable_leak_report() or talloc_enable_leak_report_full() has
been called.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void talloc_report_full(const void *ptr, FILE *f);

This provides a more detailed report than talloc_report(). It will
recursively print the ensire tree of memory referenced by the
pointer. References in the tree are shown by giving the name of the
pointer that is referenced.

You can pass NULL for the pointer, in which case a report is printed
for the top level memory context, but only if
talloc_enable_leak_report() or talloc_enable_leak_report_full() has
been called.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void talloc_enable_leak_report(void);

This enables calling of talloc_report(NULL, stderr) when the program
exits. In Samba4 this is enabled by using the --leak-report command
line option.

For it to be useful, this function must be called before any other
talloc function as it establishes a "null context" that acts as the
top of the tree. If you don't call this function first then passing
NULL to talloc_report() or talloc_report_full() won't give you the
full tree printout.

Here is a typical talloc report:

talloc report on 'null_context' (total 267 bytes in 15 blocks)
        libcli/auth/spnego_parse.c:55  contains     31 bytes in   2 blocks
        libcli/auth/spnego_parse.c:55  contains     31 bytes in   2 blocks
        iconv(UTF8,CP850)              contains     42 bytes in   2 blocks
        libcli/auth/spnego_parse.c:55  contains     31 bytes in   2 blocks
        iconv(CP850,UTF8)              contains     42 bytes in   2 blocks
        iconv(UTF8,UTF-16LE)           contains     45 bytes in   2 blocks
        iconv(UTF-16LE,UTF8)           contains     45 bytes in   2 blocks


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void talloc_enable_leak_report_full(void);

This enables calling of talloc_report_full(NULL, stderr) when the
program exits. In Samba4 this is enabled by using the
--leak-report-full command line option.

For it to be useful, this function must be called before any other
talloc function as it establishes a "null context" that acts as the
top of the tree. If you don't call this function first then passing
NULL to talloc_report() or talloc_report_full() won't give you the
full tree printout.

Here is a typical full report:

full talloc report on 'root' (total 18 bytes in 8 blocks)
    p1                             contains     18 bytes in   7 blocks (ref 0)
        r1                             contains     13 bytes in   2 blocks (ref 0)
            reference to: p2
        p2                             contains      1 bytes in   1 blocks (ref 1)
        x3                             contains      1 bytes in   1 blocks (ref 0)
        x2                             contains      1 bytes in   1 blocks (ref 0)
        x1                             contains      1 bytes in   1 blocks (ref 0)


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void talloc_enable_null_tracking(void);

This enables tracking of the NULL memory context without enabling leak
reporting on exit. Useful for when you want to do your own leak
reporting call via talloc_report_null_full();

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void talloc_disable_null_tracking(void);

This disables tracking of the NULL memory context.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
(type *)talloc_zero(const void *ctx, type);

The talloc_zero() macro is equivalent to:

  ptr = talloc(ctx, type);
  if (ptr) memset(ptr, 0, sizeof(type));


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_zero_size(const void *ctx, size_t size)

The talloc_zero_size() function is useful when you don't have a known type


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_memdup(const void *ctx, const void *p, size_t size);

The talloc_memdup() function is equivalent to:

  ptr = talloc_size(ctx, size);
  if (ptr) memcpy(ptr, p, size);


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
char *talloc_strdup(const void *ctx, const char *p);

The talloc_strdup() function is equivalent to:

  ptr = talloc_size(ctx, strlen(p)+1);
  if (ptr) memcpy(ptr, p, strlen(p)+1);

This functions sets the name of the new pointer to the passed
string. This is equivalent to:
   talloc_set_name_const(ptr, ptr)

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
char *talloc_strndup(const void *t, const char *p, size_t n);

The talloc_strndup() function is the talloc equivalent of the C
library function strndup()

This functions sets the name of the new pointer to the passed
string. This is equivalent to:
   talloc_set_name_const(ptr, ptr)

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
char *talloc_append_string(const void *t, char *orig, const char *append);

The talloc_append_string() function appends the given formatted
string to the given string.

This function sets the name of the new pointer to the new
string. This is equivalent to:
   talloc_set_name_const(ptr, ptr)

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
char *talloc_vasprintf(const void *t, const char *fmt, va_list ap);

The talloc_vasprintf() function is the talloc equivalent of the C
library function vasprintf()

This functions sets the name of the new pointer to the new
string. This is equivalent to:
   talloc_set_name_const(ptr, ptr)


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
char *talloc_asprintf(const void *t, const char *fmt, ...);

The talloc_asprintf() function is the talloc equivalent of the C
library function asprintf()

This functions sets the name of the new pointer to the new
string. This is equivalent to:
   talloc_set_name_const(ptr, ptr)


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
char *talloc_asprintf_append(char *s, const char *fmt, ...);

The talloc_asprintf_append() function appends the given formatted
string to the given string.
Use this varient when the string in the current talloc buffer may
have been truncated in length.

This functions sets the name of the new pointer to the new
string. This is equivalent to:
   talloc_set_name_const(ptr, ptr)


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
char *talloc_asprintf_append_buffer(char *s, const char *fmt, ...);

The talloc_asprintf_append() function appends the given formatted 
string to the end of the currently allocated talloc buffer.
Use this varient when the string in the current talloc buffer has
not been changed.

This functions sets the name of the new pointer to the new
string. This is equivalent to:
   talloc_set_name_const(ptr, ptr)


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
((type *)talloc_array(const void *ctx, type, uint_t count);

The talloc_array() macro is equivalent to:

  (type *)talloc_size(ctx, sizeof(type) * count);

except that it provides integer overflow protection for the multiply,
returning NULL if the multiply overflows.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_array_size(const void *ctx, size_t size, uint_t count);

The talloc_array_size() function is useful when the type is not
known. It operates in the same way as talloc_array(), but takes a size
instead of a type.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
(typeof(ptr)) talloc_array_ptrtype(const void *ctx, ptr, uint_t count);

The talloc_ptrtype() macro should be used when you have a pointer to an array
and want to allocate memory of an array to point at with this pointer. When compiling
with gcc >= 3 it is typesafe. Note this is a wrapper of talloc_array_size()
and talloc_get_name() will return the current location in the source file.
and not the type.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_realloc_fn(const void *ctx, void *ptr, size_t size);

This is a non-macro version of talloc_realloc(), which is useful 
as libraries sometimes want a ralloc function pointer. A realloc()
implementation encapsulates the functionality of malloc(), free() and
realloc() in one call, which is why it is useful to be able to pass
around a single function pointer.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_autofree_context(void);

This is a handy utility function that returns a talloc context
which will be automatically freed on program exit. This can be used
to reduce the noise in memory leak reports.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_check_name(const void *ptr, const char *name);

This function checks if a pointer has the specified name. If it does
then the pointer is returned. It it doesn't then NULL is returned.


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
(type *)talloc_get_type(const void *ptr, type);

This macro allows you to do type checking on talloc pointers. It is
particularly useful for void* private pointers. It is equivalent to
this:

   (type *)talloc_check_name(ptr, #type)


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
talloc_set_type(const void *ptr, type);

This macro allows you to force the name of a pointer to be a
particular type. This can be used in conjunction with
talloc_get_type() to do type checking on void* pointers.

It is equivalent to this:
   talloc_set_name_const(ptr, #type)

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
talloc_get_size(const void *ctx);

This function lets you know the amount of memory alloced so far by
this context. It does NOT account for subcontext memory.
This can be used to calculate the size of an array.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
void *talloc_find_parent_byname(const void *ctx, const char *name);

Find a parent memory context of the current context that has the given
name. This can be very useful in complex programs where it may be
difficult to pass all information down to the level you need, but you
know the structure you want is a parent of another context.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
(type *)talloc_find_parent_bytype(ctx, type);

Like talloc_find_parent_byname() but takes a type, making it typesafe.