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| 1 <?xml version="1.0"?> | |
| 2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis
-open.org/docbook/xml/4.2/docbookx.dtd"> | |
| 3 <refentry> | |
| 4 <refmeta> | |
| 5 <refentrytitle>talloc</refentrytitle> | |
| 6 <manvolnum>3</manvolnum> | |
| 7 </refmeta> | |
| 8 <refnamediv> | |
| 9 <refname>talloc</refname> | |
| 10 <refpurpose>hierarchical reference counted memory pool system with destructors</
refpurpose> | |
| 11 </refnamediv> | |
| 12 <refsynopsisdiv> | |
| 13 <synopsis>#include <talloc/talloc.h></synopsis> | |
| 14 </refsynopsisdiv> | |
| 15 <refsect1><title>DESCRIPTION</title> | |
| 16 <para> | |
| 17 If you are used to talloc from Samba3 then please read this | |
| 18 carefully, as talloc has changed a lot. | |
| 19 </para> | |
| 20 <para> | |
| 21 The new talloc is a hierarchical, reference counted memory pool | |
| 22 system with destructors. Quite a mouthful really, but not too bad | |
| 23 once you get used to it. | |
| 24 </para> | |
| 25 <para> | |
| 26 Perhaps the biggest change from Samba3 is that there is no | |
| 27 distinction between a "talloc context" and a "talloc pointer". Any | |
| 28 pointer returned from talloc() is itself a valid talloc context. | |
| 29 This means you can do this: | |
| 30 </para> | |
| 31 <programlisting> | |
| 32 struct foo *X = talloc(mem_ctx, struct foo); | |
| 33 X->name = talloc_strdup(X, "foo"); | |
| 34 </programlisting> | |
| 35 <para> | |
| 36 and the pointer <literal role="code">X->name</literal> | |
| 37 would be a "child" of the talloc context <literal | |
| 38 role="code">X</literal> which is itself a child of | |
| 39 <literal role="code">mem_ctx</literal>. So if you do | |
| 40 <literal role="code">talloc_free(mem_ctx)</literal> then | |
| 41 it is all destroyed, whereas if you do <literal | |
| 42 role="code">talloc_free(X)</literal> then just <literal | |
| 43 role="code">X</literal> and <literal | |
| 44 role="code">X->name</literal> are destroyed, and if | |
| 45 you do <literal | |
| 46 role="code">talloc_free(X->name)</literal> then just | |
| 47 the name element of <literal role="code">X</literal> is | |
| 48 destroyed. | |
| 49 </para> | |
| 50 <para> | |
| 51 If you think about this, then what this effectively gives you is an | |
| 52 n-ary tree, where you can free any part of the tree with | |
| 53 talloc_free(). | |
| 54 </para> | |
| 55 <para> | |
| 56 If you find this confusing, then I suggest you run the <literal | |
| 57 role="code">testsuite</literal> program to watch talloc | |
| 58 in action. You may also like to add your own tests to <literal | |
| 59 role="code">testsuite.c</literal> to clarify how some | |
| 60 particular situation is handled. | |
| 61 </para> | |
| 62 </refsect1> | |
| 63 <refsect1><title>TALLOC API</title> | |
| 64 <para> | |
| 65 The following is a complete guide to the talloc API. Read it all at | |
| 66 least twice. | |
| 67 </para> | |
| 68 <refsect2><title>(type *)talloc(const void *ctx, type);</title> | |
| 69 <para> | |
| 70 The talloc() macro is the core of the talloc library. It takes a | |
| 71 memory <emphasis role="italic">ctx</emphasis> and a <emphasis | |
| 72 role="italic">type</emphasis>, and returns a pointer to a new | |
| 73 area of memory of the given <emphasis | |
| 74 role="italic">type</emphasis>. | |
| 75 </para> | |
| 76 <para> | |
| 77 The returned pointer is itself a talloc context, so you can use | |
| 78 it as the <emphasis role="italic">ctx</emphasis> argument to more | |
| 79 calls to talloc() if you wish. | |
| 80 </para> | |
| 81 <para> | |
| 82 The returned pointer is a "child" of the supplied context. This | |
| 83 means that if you talloc_free() the <emphasis | |
| 84 role="italic">ctx</emphasis> then the new child disappears as | |
| 85 well. Alternatively you can free just the child. | |
| 86 </para> | |
| 87 <para> | |
| 88 The <emphasis role="italic">ctx</emphasis> argument to talloc() | |
| 89 can be NULL, in which case a new top level context is created. | |
| 90 </para> | |
| 91 </refsect2> | |
| 92 <refsect2><title>void *talloc_size(const void *ctx, size_t size);</title> | |
| 93 <para> | |
| 94 The function talloc_size() should be used when you don't have a | |
| 95 convenient type to pass to talloc(). Unlike talloc(), it is not | |
| 96 type safe (as it returns a void *), so you are on your own for | |
| 97 type checking. | |
| 98 </para> | |
| 99 </refsect2> | |
| 100 <refsect2><title>(typeof(ptr)) talloc_ptrtype(const void *ctx, ptr);</title> | |
| 101 <para> | |
| 102 The talloc_ptrtype() macro should be used when you have a pointer and | |
| 103 want to allocate memory to point at with this pointer. When compiling | |
| 104 with gcc >= 3 it is typesafe. Note this is a wrapper of talloc_size() | |
| 105 and talloc_get_name() will return the current location in the source f
ile. | |
| 106 and not the type. | |
| 107 </para> | |
| 108 </refsect2> | |
| 109 <refsect2><title>int talloc_free(void *ptr);</title> | |
| 110 <para> | |
| 111 The talloc_free() function frees a piece of talloc memory, and | |
| 112 all its children. You can call talloc_free() on any pointer | |
| 113 returned by talloc(). | |
| 114 </para> | |
| 115 <para> | |
| 116 The return value of talloc_free() indicates success or failure, | |
| 117 with 0 returned for success and -1 for failure. The only | |
| 118 possible failure condition is if <emphasis | |
| 119 role="italic">ptr</emphasis> had a destructor attached to it and | |
| 120 the destructor returned -1. See <link | |
| 121 linkend="talloc_set_destructor"><quote>talloc_set_destructor()</quote>
</link> | |
| 122 for details on destructors. | |
| 123 </para> | |
| 124 <para> | |
| 125 If this pointer has an additional parent when talloc_free() is | |
| 126 called then the memory is not actually released, but instead the | |
| 127 most recently established parent is destroyed. See <link | |
| 128 linkend="talloc_reference"><quote>talloc_reference()</quote></link> | |
| 129 for details on establishing additional parents. | |
| 130 </para> | |
| 131 <para> | |
| 132 For more control on which parent is removed, see <link | |
| 133 linkend="talloc_unlink"><quote>talloc_unlink()</quote></link>. | |
| 134 </para> | |
| 135 <para> | |
| 136 talloc_free() operates recursively on its children. | |
| 137 </para> | |
| 138 <para> | |
| 139 From the 2.0 version of talloc, as a special case, | |
| 140 talloc_free() is refused on pointers that have more than one | |
| 141 parent, as talloc would have no way of knowing which parent | |
| 142 should be removed. To free a pointer that has more than one | |
| 143 parent please use talloc_unlink(). | |
| 144 </para> | |
| 145 <para> | |
| 146 To help you find problems in your code caused by this behaviour, if | |
| 147 you do try and free a pointer with more than one parent then the | |
| 148 talloc logging function will be called to give output like this: | |
| 149 </para> | |
| 150 <para> | |
| 151 <screen format="linespecific"> | |
| 152 ERROR: talloc_free with references at some_dir/source/foo.c:123 | |
| 153 reference at some_dir/source/other.c:325 | |
| 154 reference at some_dir/source/third.c:121 | |
| 155 </screen> | |
| 156 </para> | |
| 157 <para> | |
| 158 Please see the documentation for talloc_set_log_fn() and | |
| 159 talloc_set_log_stderr() for more information on talloc logging | |
| 160 functions. | |
| 161 </para> | |
| 162 </refsect2> | |
| 163 <refsect2 id="talloc_reference"><title>void *talloc_reference(const void *ct
x, const void *ptr);</title> | |
| 164 <para> | |
| 165 The talloc_reference() function makes <emphasis | |
| 166 role="italic">ctx</emphasis> an additional parent of <emphasis | |
| 167 role="italic">ptr</emphasis>. | |
| 168 </para> | |
| 169 <para> | |
| 170 The return value of talloc_reference() is always the original | |
| 171 pointer <emphasis role="italic">ptr</emphasis>, unless talloc ran | |
| 172 out of memory in creating the reference in which case it will | |
| 173 return NULL (each additional reference consumes around 48 bytes | |
| 174 of memory on intel x86 platforms). | |
| 175 </para> | |
| 176 <para> | |
| 177 If <emphasis role="italic">ptr</emphasis> is NULL, then the | |
| 178 function is a no-op, and simply returns NULL. | |
| 179 </para> | |
| 180 <para> | |
| 181 After creating a reference you can free it in one of the | |
| 182 following ways: | |
| 183 </para> | |
| 184 <para> | |
| 185 <itemizedlist> | |
| 186 <listitem> | |
| 187 <para> | |
| 188 you can talloc_free() any parent of the original pointer. | |
| 189 That will reduce the number of parents of this pointer by 1, | |
| 190 and will cause this pointer to be freed if it runs out of | |
| 191 parents. | |
| 192 </para> | |
| 193 </listitem> | |
| 194 <listitem> | |
| 195 <para> | |
| 196 you can talloc_free() the pointer itself. That will destroy | |
| 197 the most recently established parent to the pointer and leave | |
| 198 the pointer as a child of its current parent. | |
| 199 </para> | |
| 200 </listitem> | |
| 201 </itemizedlist> | |
| 202 </para> | |
| 203 <para> | |
| 204 For more control on which parent to remove, see <link | |
| 205 linkend="talloc_unlink"><quote>talloc_unlink()</quote></link>. | |
| 206 </para> | |
| 207 </refsect2> | |
| 208 <refsect2 id="talloc_unlink"><title>int talloc_unlink(const void *ctx, const
void *ptr);</title> | |
| 209 <para> | |
| 210 The talloc_unlink() function removes a specific parent from | |
| 211 <emphasis role="italic">ptr</emphasis>. The <emphasis | |
| 212 role="italic">ctx</emphasis> passed must either be a context used | |
| 213 in talloc_reference() with this pointer, or must be a direct | |
| 214 parent of ptr. | |
| 215 </para> | |
| 216 <para> | |
| 217 Note that if the parent has already been removed using | |
| 218 talloc_free() then this function will fail and will return -1. | |
| 219 Likewise, if <emphasis role="italic">ptr</emphasis> is NULL, then | |
| 220 the function will make no modifications and return -1. | |
| 221 </para> | |
| 222 <para> | |
| 223 Usually you can just use talloc_free() instead of | |
| 224 talloc_unlink(), but sometimes it is useful to have the | |
| 225 additional control on which parent is removed. | |
| 226 </para> | |
| 227 </refsect2> | |
| 228 <refsect2 id="talloc_set_destructor"><title>void talloc_set_destructor(const
void *ptr, int (*destructor)(void *));</title> | |
| 229 <para> | |
| 230 The function talloc_set_destructor() sets the <emphasis | |
| 231 role="italic">destructor</emphasis> for the pointer <emphasis | |
| 232 role="italic">ptr</emphasis>. A <emphasis | |
| 233 role="italic">destructor</emphasis> is a function that is called | |
| 234 when the memory used by a pointer is about to be released. The | |
| 235 destructor receives <emphasis role="italic">ptr</emphasis> as an | |
| 236 argument, and should return 0 for success and -1 for failure. | |
| 237 </para> | |
| 238 <para> | |
| 239 The <emphasis role="italic">destructor</emphasis> can do anything | |
| 240 it wants to, including freeing other pieces of memory. A common | |
| 241 use for destructors is to clean up operating system resources | |
| 242 (such as open file descriptors) contained in the structure the | |
| 243 destructor is placed on. | |
| 244 </para> | |
| 245 <para> | |
| 246 You can only place one destructor on a pointer. If you need more | |
| 247 than one destructor then you can create a zero-length child of | |
| 248 the pointer and place an additional destructor on that. | |
| 249 </para> | |
| 250 <para> | |
| 251 To remove a destructor call talloc_set_destructor() with NULL for | |
| 252 the destructor. | |
| 253 </para> | |
| 254 <para> | |
| 255 If your destructor attempts to talloc_free() the pointer that it | |
| 256 is the destructor for then talloc_free() will return -1 and the | |
| 257 free will be ignored. This would be a pointless operation | |
| 258 anyway, as the destructor is only called when the memory is just | |
| 259 about to go away. | |
| 260 </para> | |
| 261 </refsect2> | |
| 262 <refsect2><title>int talloc_increase_ref_count(const void *<emphasis role="i
talic">ptr</emphasis>);</title> | |
| 263 <para> | |
| 264 The talloc_increase_ref_count(<emphasis | |
| 265 role="italic">ptr</emphasis>) function is exactly equivalent to: | |
| 266 </para> | |
| 267 <programlisting>talloc_reference(NULL, ptr);</programlisting> | |
| 268 <para> | |
| 269 You can use either syntax, depending on which you think is | |
| 270 clearer in your code. | |
| 271 </para> | |
| 272 <para> | |
| 273 It returns 0 on success and -1 on failure. | |
| 274 </para> | |
| 275 </refsect2> | |
| 276 <refsect2><title>size_t talloc_reference_count(const void *<emphasis role="i
talic">ptr</emphasis>);</title> | |
| 277 <para> | |
| 278 Return the number of references to the pointer. | |
| 279 </para> | |
| 280 </refsect2> | |
| 281 <refsect2 id="talloc_set_name"><title>void talloc_set_name(const void *ptr,
const char *fmt, ...);</title> | |
| 282 <para> | |
| 283 Each talloc pointer has a "name". The name is used principally | |
| 284 for debugging purposes, although it is also possible to set and | |
| 285 get the name on a pointer in as a way of "marking" pointers in | |
| 286 your code. | |
| 287 </para> | |
| 288 <para> | |
| 289 The main use for names on pointer is for "talloc reports". See | |
| 290 <link | |
| 291 linkend="talloc_report"><quote>talloc_report_depth_cb()</quote></link>
, | |
| 292 <link | |
| 293 linkend="talloc_report"><quote>talloc_report_depth_file()</quote></lin
k>, | |
| 294 <link | |
| 295 linkend="talloc_report"><quote>talloc_report()</quote></link> | |
| 296 <link | |
| 297 linkend="talloc_report"><quote>talloc_report()</quote></link> | |
| 298 and <link | |
| 299 linkend="talloc_report_full"><quote>talloc_report_full()</quote></link
> | |
| 300 for details. Also see <link | |
| 301 linkend="talloc_enable_leak_report"><quote>talloc_enable_leak_report()
</quote></link> | |
| 302 and <link | |
| 303 linkend="talloc_enable_leak_report_full"><quote>talloc_enable_leak_rep
ort_full()</quote></link>. | |
| 304 </para> | |
| 305 <para> | |
| 306 The talloc_set_name() function allocates memory as a child of the | |
| 307 pointer. It is logically equivalent to: | |
| 308 </para> | |
| 309 <programlisting>talloc_set_name_const(ptr, talloc_asprintf(ptr, fmt, ...
));</programlisting> | |
| 310 <para> | |
| 311 Note that multiple calls to talloc_set_name() will allocate more | |
| 312 memory without releasing the name. All of the memory is released | |
| 313 when the ptr is freed using talloc_free(). | |
| 314 </para> | |
| 315 </refsect2> | |
| 316 <refsect2><title>void talloc_set_name_const(const void *<emphasis role="ital
ic">ptr</emphasis>, const char *<emphasis role="italic">name</emphasis>);</title
> | |
| 317 <para> | |
| 318 The function talloc_set_name_const() is just like | |
| 319 talloc_set_name(), but it takes a string constant, and is much | |
| 320 faster. It is extensively used by the "auto naming" macros, such | |
| 321 as talloc_p(). | |
| 322 </para> | |
| 323 <para> | |
| 324 This function does not allocate any memory. It just copies the | |
| 325 supplied pointer into the internal representation of the talloc | |
| 326 ptr. This means you must not pass a <emphasis | |
| 327 role="italic">name</emphasis> pointer to memory that will | |
| 328 disappear before <emphasis role="italic">ptr</emphasis> is freed | |
| 329 with talloc_free(). | |
| 330 </para> | |
| 331 </refsect2> | |
| 332 <refsect2><title>void *talloc_named(const void *<emphasis role="italic">ctx<
/emphasis>, size_t <emphasis role="italic">size</emphasis>, const char *<emphasi
s role="italic">fmt</emphasis>, ...);</title> | |
| 333 <para> | |
| 334 The talloc_named() function creates a named talloc pointer. It | |
| 335 is equivalent to: | |
| 336 </para> | |
| 337 <programlisting>ptr = talloc_size(ctx, size); | |
| 338 talloc_set_name(ptr, fmt, ....);</programlisting> | |
| 339 </refsect2> | |
| 340 <refsect2><title>void *talloc_named_const(const void *<emphasis role="italic
">ctx</emphasis>, size_t <emphasis role="italic">size</emphasis>, const char *<e
mphasis role="italic">name</emphasis>);</title> | |
| 341 <para> | |
| 342 This is equivalent to: | |
| 343 </para> | |
| 344 <programlisting>ptr = talloc_size(ctx, size); | |
| 345 talloc_set_name_const(ptr, name);</programlisting> | |
| 346 </refsect2> | |
| 347 <refsect2><title>const char *talloc_get_name(const void *<emphasis role="ita
lic">ptr</emphasis>);</title> | |
| 348 <para> | |
| 349 This returns the current name for the given talloc pointer, | |
| 350 <emphasis role="italic">ptr</emphasis>. See <link | |
| 351 linkend="talloc_set_name"><quote>talloc_set_name()</quote></link> | |
| 352 for details. | |
| 353 </para> | |
| 354 </refsect2> | |
| 355 <refsect2><title>void *talloc_init(const char *<emphasis role="italic">fmt</
emphasis>, ...);</title> | |
| 356 <para> | |
| 357 This function creates a zero length named talloc context as a top | |
| 358 level context. It is equivalent to: | |
| 359 </para> | |
| 360 <programlisting>talloc_named(NULL, 0, fmt, ...);</programlisting> | |
| 361 </refsect2> | |
| 362 <refsect2><title>void *talloc_new(void *<emphasis role="italic">ctx</emphasi
s>);</title> | |
| 363 <para> | |
| 364 This is a utility macro that creates a new memory context hanging | |
| 365 off an exiting context, automatically naming it "talloc_new: | |
| 366 __location__" where __location__ is the source line it is called | |
| 367 from. It is particularly useful for creating a new temporary | |
| 368 working context. | |
| 369 </para> | |
| 370 </refsect2> | |
| 371 <refsect2><title>(<emphasis role="italic">type</emphasis> *)talloc_realloc(c
onst void *<emphasis role="italic">ctx</emphasis>, void *<emphasis role="italic"
>ptr</emphasis>, <emphasis role="italic">type</emphasis>, <emphasis role="italic
">count</emphasis>);</title> | |
| 372 <para> | |
| 373 The talloc_realloc() macro changes the size of a talloc pointer. | |
| 374 It has the following equivalences: | |
| 375 </para> | |
| 376 <programlisting>talloc_realloc(ctx, NULL, type, 1) ==> talloc(ctx, type)
; | |
| 377 talloc_realloc(ctx, ptr, type, 0) ==> talloc_free(ptr);</programlisting> | |
| 378 <para> | |
| 379 The <emphasis role="italic">ctx</emphasis> argument is only used | |
| 380 if <emphasis role="italic">ptr</emphasis> is not NULL, otherwise | |
| 381 it is ignored. | |
| 382 </para> | |
| 383 <para> | |
| 384 talloc_realloc() returns the new pointer, or NULL on failure. | |
| 385 The call will fail either due to a lack of memory, or because the | |
| 386 pointer has more than one parent (see <link | |
| 387 linkend="talloc_reference"><quote>talloc_reference()</quote></link>). | |
| 388 </para> | |
| 389 </refsect2> | |
| 390 <refsect2><title>void *talloc_realloc_size(const void *ctx, void *ptr, size_
t size);</title> | |
| 391 <para> | |
| 392 the talloc_realloc_size() function is useful when the type is not | |
| 393 known so the type-safe talloc_realloc() cannot be used. | |
| 394 </para> | |
| 395 </refsect2> | |
| 396 <refsect2><title>TYPE *talloc_steal(const void *<emphasis role="italic">new_
ctx</emphasis>, const TYPE *<emphasis role="italic">ptr</emphasis>);</title> | |
| 397 <para> | |
| 398 The talloc_steal() function changes the parent context of a | |
| 399 talloc pointer. It is typically used when the context that the | |
| 400 pointer is currently a child of is going to be freed and you wish | |
| 401 to keep the memory for a longer time. | |
| 402 </para> | |
| 403 <para> | |
| 404 The talloc_steal() function returns the pointer that you pass it. | |
| 405 It does not have any failure modes. | |
| 406 </para> | |
| 407 <para> | |
| 408 It is possible to produce loops in the parent/child | |
| 409 relationship if you are not careful with talloc_steal(). No | |
| 410 guarantees are provided as to your sanity or the safety of your | |
| 411 data if you do this. | |
| 412 </para> | |
| 413 <para> | |
| 414 Note that if you try and call talloc_steal() on a pointer that has | |
| 415 more than one parent then the result is ambiguous. Talloc will choose | |
| 416 to remove the parent that is currently indicated by talloc_parent() | |
| 417 and replace it with the chosen parent. You will also get a message | |
| 418 like this via the talloc logging functions: | |
| 419 </para> | |
| 420 <para> | |
| 421 <screen format="linespecific"> | |
| 422 WARNING: talloc_steal with references at some_dir/source/foo.c:123 | |
| 423 reference at some_dir/source/other.c:325 | |
| 424 reference at some_dir/source/third.c:121 | |
| 425 </screen> | |
| 426 </para> | |
| 427 <para> | |
| 428 To unambiguously change the parent of a pointer please see | |
| 429 the | |
| 430 function <link linkend="talloc_reference"><quote>talloc_reparent()</qu
ote></link>. See | |
| 431 the talloc_set_log_fn() documentation for more information | |
| 432 on talloc logging. | |
| 433 </para> | |
| 434 </refsect2> | |
| 435 <refsect2><title>TYPE *talloc_reparent(const void *<emphasis role="italic">o
ld_parent</emphasis>, const void *<emphasis role="italic">new_parent</emphasis>,
const TYPE *<emphasis role="italic">ptr</emphasis>);</title> | |
| 436 <para> | |
| 437 The talloc_reparent() function changes the parent context of a talloc | |
| 438 pointer. It is typically used when the context that the pointer is | |
| 439 currently a child of is going to be freed and you wish to keep the | |
| 440 memory for a longer time. | |
| 441 </para> | |
| 442 <para> | |
| 443 The talloc_reparent() function returns the pointer that you pass it. I
t | |
| 444 does not have any failure modes. | |
| 445 </para> | |
| 446 <para> | |
| 447 The difference between talloc_reparent() and talloc_steal() is that | |
| 448 talloc_reparent() can specify which parent you wish to change. This is | |
| 449 useful when a pointer has multiple parents via references. | |
| 450 </para> | |
| 451 </refsect2> | |
| 452 <refsect2><title>TYPE *talloc_move(const void *<emphasis role="italic">new_c
tx</emphasis>, TYPE **<emphasis role="italic">ptr</emphasis>);</title> | |
| 453 <para> | |
| 454 The talloc_move() function is a wrapper around | |
| 455 talloc_steal() which zeros the source pointer after the | |
| 456 move. This avoids a potential source of bugs where a | |
| 457 programmer leaves a pointer in two structures, and uses the | |
| 458 pointer from the old structure after it has been moved to a | |
| 459 new one. | |
| 460 </para> | |
| 461 </refsect2> | |
| 462 <refsect2><title>size_t talloc_total_size(const void *<emphasis role="italic
">ptr</emphasis>);</title> | |
| 463 <para> | |
| 464 The talloc_total_size() function returns the total size in bytes | |
| 465 used by this pointer and all child pointers. Mostly useful for | |
| 466 debugging. | |
| 467 </para> | |
| 468 <para> | |
| 469 Passing NULL is allowed, but it will only give a meaningful | |
| 470 result if talloc_enable_leak_report() or | |
| 471 talloc_enable_leak_report_full() has been called. | |
| 472 </para> | |
| 473 </refsect2> | |
| 474 <refsect2><title>size_t talloc_total_blocks(const void *<emphasis role="ital
ic">ptr</emphasis>);</title> | |
| 475 <para> | |
| 476 The talloc_total_blocks() function returns the total memory block | |
| 477 count used by this pointer and all child pointers. Mostly useful | |
| 478 for debugging. | |
| 479 </para> | |
| 480 <para> | |
| 481 Passing NULL is allowed, but it will only give a meaningful | |
| 482 result if talloc_enable_leak_report() or | |
| 483 talloc_enable_leak_report_full() has been called. | |
| 484 </para> | |
| 485 </refsect2> | |
| 486 <refsect2 id="talloc_report"><title>void talloc_report(const void *ptr, FILE
*f);</title> | |
| 487 <para> | |
| 488 The talloc_report() function prints a summary report of all | |
| 489 memory used by <emphasis role="italic">ptr</emphasis>. One line | |
| 490 of report is printed for each immediate child of ptr, showing the | |
| 491 total memory and number of blocks used by that child. | |
| 492 </para> | |
| 493 <para> | |
| 494 You can pass NULL for the pointer, in which case a report is | |
| 495 printed for the top level memory context, but only if | |
| 496 talloc_enable_leak_report() or talloc_enable_leak_report_full() | |
| 497 has been called. | |
| 498 </para> | |
| 499 </refsect2> | |
| 500 <refsect2 id="talloc_report_full"><title>void talloc_report_full(const void
*<emphasis role="italic">ptr</emphasis>, FILE *<emphasis role="italic">f</emphas
is>);</title> | |
| 501 <para> | |
| 502 This provides a more detailed report than talloc_report(). It | |
| 503 will recursively print the entire tree of memory referenced by | |
| 504 the pointer. References in the tree are shown by giving the name | |
| 505 of the pointer that is referenced. | |
| 506 </para> | |
| 507 <para> | |
| 508 You can pass NULL for the pointer, in which case a report is | |
| 509 printed for the top level memory context, but only if | |
| 510 talloc_enable_leak_report() or talloc_enable_leak_report_full() | |
| 511 has been called. | |
| 512 </para> | |
| 513 </refsect2> | |
| 514 <refsect2 id="talloc_report_depth_cb"> | |
| 515 <funcsynopsis><funcprototype> | |
| 516 <funcdef>void <function>talloc_report_depth_cb</function></funcdef> | |
| 517 <paramdef><parameter>const void *ptr</parameter></paramdef> | |
| 518 <paramdef><parameter>int depth</parameter></paramdef> | |
| 519 <paramdef><parameter>int max_depth</parameter></paramdef> | |
| 520 <paramdef><parameter>void (*callback)(const void *ptr, int depth, int max_
depth, int is_ref, void *priv)</parameter></paramdef> | |
| 521 <paramdef><parameter>void *priv</parameter></paramdef> | |
| 522 </funcprototype></funcsynopsis> | |
| 523 <para> | |
| 524 This provides a more flexible reports than talloc_report(). It | |
| 525 will recursively call the callback for the entire tree of memory | |
| 526 referenced by the pointer. References in the tree are passed with | |
| 527 <emphasis role="italic">is_ref = 1</emphasis> and the pointer that is
referenced. | |
| 528 </para> | |
| 529 <para> | |
| 530 You can pass NULL for the pointer, in which case a report is | |
| 531 printed for the top level memory context, but only if | |
| 532 talloc_enable_leak_report() or talloc_enable_leak_report_full() | |
| 533 has been called. | |
| 534 </para> | |
| 535 <para> | |
| 536 The recursion is stopped when depth >= max_depth. | |
| 537 max_depth = -1 means only stop at leaf nodes. | |
| 538 </para> | |
| 539 </refsect2> | |
| 540 <refsect2 id="talloc_report_depth_file"> | |
| 541 <funcsynopsis><funcprototype> | |
| 542 <funcdef>void <function>talloc_report_depth_file</function></funcdef> | |
| 543 <paramdef><parameter>const void *ptr</parameter></paramdef> | |
| 544 <paramdef><parameter>int depth</parameter></paramdef> | |
| 545 <paramdef><parameter>int max_depth</parameter></paramdef> | |
| 546 <paramdef><parameter>FILE *f</parameter></paramdef> | |
| 547 </funcprototype></funcsynopsis> | |
| 548 <para> | |
| 549 This provides a more flexible reports than talloc_report(). It | |
| 550 will let you specify the depth and max_depth. | |
| 551 </para> | |
| 552 </refsect2> | |
| 553 <refsect2 id="talloc_enable_leak_report"><title>void talloc_enable_leak_repo
rt(void);</title> | |
| 554 <para> | |
| 555 This enables calling of talloc_report(NULL, stderr) when the | |
| 556 program exits. In Samba4 this is enabled by using the | |
| 557 --leak-report command line option. | |
| 558 </para> | |
| 559 <para> | |
| 560 For it to be useful, this function must be called before any | |
| 561 other talloc function as it establishes a "null context" that | |
| 562 acts as the top of the tree. If you don't call this function | |
| 563 first then passing NULL to talloc_report() or | |
| 564 talloc_report_full() won't give you the full tree printout. | |
| 565 </para> | |
| 566 <para> | |
| 567 Here is a typical talloc report: | |
| 568 </para> | |
| 569 <screen format="linespecific">talloc report on 'null_context' (total 267
bytes in 15 blocks) | |
| 570 libcli/auth/spnego_parse.c:55 contains 31 bytes in 2 blocks | |
| 571 libcli/auth/spnego_parse.c:55 contains 31 bytes in 2 blocks | |
| 572 iconv(UTF8,CP850) contains 42 bytes in 2 blocks | |
| 573 libcli/auth/spnego_parse.c:55 contains 31 bytes in 2 blocks | |
| 574 iconv(CP850,UTF8) contains 42 bytes in 2 blocks | |
| 575 iconv(UTF8,UTF-16LE) contains 45 bytes in 2 blocks | |
| 576 iconv(UTF-16LE,UTF8) contains 45 bytes in 2 blocks | |
| 577 </screen> | |
| 578 </refsect2> | |
| 579 <refsect2 id="talloc_enable_leak_report_full"><title>void talloc_enable_leak
_report_full(void);</title> | |
| 580 <para> | |
| 581 This enables calling of talloc_report_full(NULL, stderr) when the | |
| 582 program exits. In Samba4 this is enabled by using the | |
| 583 --leak-report-full command line option. | |
| 584 </para> | |
| 585 <para> | |
| 586 For it to be useful, this function must be called before any | |
| 587 other talloc function as it establishes a "null context" that | |
| 588 acts as the top of the tree. If you don't call this function | |
| 589 first then passing NULL to talloc_report() or | |
| 590 talloc_report_full() won't give you the full tree printout. | |
| 591 </para> | |
| 592 <para> | |
| 593 Here is a typical full report: | |
| 594 </para> | |
| 595 <screen format="linespecific">full talloc report on 'root' (total 18 byt
es in 8 blocks) | |
| 596 p1 contains 18 bytes in 7 blocks (ref 0) | |
| 597 r1 contains 13 bytes in 2 blocks (ref 0) | |
| 598 reference to: p2 | |
| 599 p2 contains 1 bytes in 1 blocks (ref 1) | |
| 600 x3 contains 1 bytes in 1 blocks (ref 0) | |
| 601 x2 contains 1 bytes in 1 blocks (ref 0) | |
| 602 x1 contains 1 bytes in 1 blocks (ref 0) | |
| 603 </screen> | |
| 604 </refsect2> | |
| 605 <refsect2><title>(<emphasis role="italic">type</emphasis> *)talloc_zero(cons
t void *<emphasis role="italic">ctx</emphasis>, <emphasis role="italic">type</em
phasis>);</title> | |
| 606 <para> | |
| 607 The talloc_zero() macro is equivalent to: | |
| 608 </para> | |
| 609 <programlisting>ptr = talloc(ctx, type); | |
| 610 if (ptr) memset(ptr, 0, sizeof(type));</programlisting> | |
| 611 </refsect2> | |
| 612 <refsect2><title>void *talloc_zero_size(const void *<emphasis role="italic">
ctx</emphasis>, size_t <emphasis role="italic">size</emphasis>)</title> | |
| 613 <para> | |
| 614 The talloc_zero_size() function is useful when you don't have a | |
| 615 known type. | |
| 616 </para> | |
| 617 </refsect2> | |
| 618 <refsect2><title>void *talloc_memdup(const void *<emphasis role="italic">ctx
</emphasis>, const void *<emphasis role="italic">p</emphasis>, size_t size);</ti
tle> | |
| 619 <para> | |
| 620 The talloc_memdup() function is equivalent to: | |
| 621 </para> | |
| 622 <programlisting>ptr = talloc_size(ctx, size); | |
| 623 if (ptr) memcpy(ptr, p, size);</programlisting> | |
| 624 </refsect2> | |
| 625 <refsect2><title>char *talloc_strdup(const void *<emphasis role="italic">ctx
</emphasis>, const char *<emphasis role="italic">p</emphasis>);</title> | |
| 626 <para> | |
| 627 The talloc_strdup() function is equivalent to: | |
| 628 </para> | |
| 629 <programlisting>ptr = talloc_size(ctx, strlen(p)+1); | |
| 630 if (ptr) memcpy(ptr, p, strlen(p)+1);</programlisting> | |
| 631 <para> | |
| 632 This function sets the name of the new pointer to the passed | |
| 633 string. This is equivalent to: | |
| 634 </para> | |
| 635 <programlisting>talloc_set_name_const(ptr, ptr)</programlisting> | |
| 636 </refsect2> | |
| 637 <refsect2><title>char *talloc_strndup(const void *<emphasis role="italic">t<
/emphasis>, const char *<emphasis role="italic">p</emphasis>, size_t <emphasis r
ole="italic">n</emphasis>);</title> | |
| 638 <para> | |
| 639 The talloc_strndup() function is the talloc equivalent of the C | |
| 640 library function strndup(3). | |
| 641 </para> | |
| 642 <para> | |
| 643 This function sets the name of the new pointer to the passed | |
| 644 string. This is equivalent to: | |
| 645 </para> | |
| 646 <programlisting>talloc_set_name_const(ptr, ptr)</programlisting> | |
| 647 </refsect2> | |
| 648 <refsect2><title>char *talloc_append_string(const void *<emphasis role="ital
ic">t</emphasis>, char *<emphasis role="italic">orig</emphasis>, const char *<em
phasis role="italic">append</emphasis>);</title> | |
| 649 <para> | |
| 650 The talloc_append_string() function appends the given formatted | |
| 651 string to the given string. | |
| 652 </para> | |
| 653 <para> | |
| 654 This function sets the name of the new pointer to the new | |
| 655 string. This is equivalent to: | |
| 656 </para> | |
| 657 <programlisting>talloc_set_name_const(ptr, ptr)</programlisting> | |
| 658 </refsect2> | |
| 659 <refsect2><title>char *talloc_vasprintf(const void *<emphasis role="italic">
t</emphasis>, const char *<emphasis role="italic">fmt</emphasis>, va_list <empha
sis role="italic">ap</emphasis>);</title> | |
| 660 <para> | |
| 661 The talloc_vasprintf() function is the talloc equivalent of the C | |
| 662 library function vasprintf(3). | |
| 663 </para> | |
| 664 <para> | |
| 665 This function sets the name of the new pointer to the new | |
| 666 string. This is equivalent to: | |
| 667 </para> | |
| 668 <programlisting>talloc_set_name_const(ptr, ptr)</programlisting> | |
| 669 </refsect2> | |
| 670 <refsect2><title>char *talloc_asprintf(const void *<emphasis role="italic">t
</emphasis>, const char *<emphasis role="italic">fmt</emphasis>, ...);</title> | |
| 671 <para> | |
| 672 The talloc_asprintf() function is the talloc equivalent of the C | |
| 673 library function asprintf(3). | |
| 674 </para> | |
| 675 <para> | |
| 676 This function sets the name of the new pointer to the passed | |
| 677 string. This is equivalent to: | |
| 678 </para> | |
| 679 <programlisting>talloc_set_name_const(ptr, ptr)</programlisting> | |
| 680 </refsect2> | |
| 681 <refsect2><title>char *talloc_asprintf_append(char *s, const char *fmt, ...)
;</title> | |
| 682 <para> | |
| 683 The talloc_asprintf_append() function appends the given formatted | |
| 684 string to the given string. | |
| 685 </para> | |
| 686 <para> | |
| 687 This function sets the name of the new pointer to the new | |
| 688 string. This is equivalent to: | |
| 689 </para> | |
| 690 <programlisting>talloc_set_name_const(ptr, ptr)</programlisting> | |
| 691 </refsect2> | |
| 692 <refsect2><title>(type *)talloc_array(const void *ctx, type, uint_t count);<
/title> | |
| 693 <para> | |
| 694 The talloc_array() macro is equivalent to: | |
| 695 </para> | |
| 696 <programlisting>(type *)talloc_size(ctx, sizeof(type) * count);</program
listing> | |
| 697 <para> | |
| 698 except that it provides integer overflow protection for the | |
| 699 multiply, returning NULL if the multiply overflows. | |
| 700 </para> | |
| 701 </refsect2> | |
| 702 <refsect2><title>void *talloc_array_size(const void *ctx, size_t size, uint_
t count);</title> | |
| 703 <para> | |
| 704 The talloc_array_size() function is useful when the type is not | |
| 705 known. It operates in the same way as talloc_array(), but takes a | |
| 706 size instead of a type. | |
| 707 </para> | |
| 708 </refsect2> | |
| 709 <refsect2><title>(typeof(ptr)) talloc_array_ptrtype(const void *ctx, ptr, ui
nt_t count);</title> | |
| 710 <para> | |
| 711 The talloc_ptrtype() macro should be used when you have a pointer to a
n array | |
| 712 and want to allocate memory of an array to point at with this pointer.
When compiling | |
| 713 with gcc >= 3 it is typesafe. Note this is a wrapper of talloc_array_s
ize() | |
| 714 and talloc_get_name() will return the current location in the source f
ile. | |
| 715 and not the type. | |
| 716 </para> | |
| 717 </refsect2> | |
| 718 <refsect2><title>void *talloc_realloc_fn(const void *ctx, void *ptr, size_t
size)</title> | |
| 719 <para> | |
| 720 This is a non-macro version of talloc_realloc(), which is useful | |
| 721 as libraries sometimes want a realloc function pointer. A | |
| 722 realloc(3) implementation encapsulates the functionality of | |
| 723 malloc(3), free(3) and realloc(3) in one call, which is why it is | |
| 724 useful to be able to pass around a single function pointer. | |
| 725 </para> | |
| 726 </refsect2> | |
| 727 <refsect2><title>void *talloc_autofree_context(void);</title> | |
| 728 <para> | |
| 729 This is a handy utility function that returns a talloc context | |
| 730 which will be automatically freed on program exit. This can be | |
| 731 used to reduce the noise in memory leak reports. | |
| 732 </para> | |
| 733 </refsect2> | |
| 734 <refsect2><title>void *talloc_check_name(const void *ptr, const char *name);
</title> | |
| 735 <para> | |
| 736 This function checks if a pointer has the specified <emphasis | |
| 737 role="italic">name</emphasis>. If it does then the pointer is | |
| 738 returned. It it doesn't then NULL is returned. | |
| 739 </para> | |
| 740 </refsect2> | |
| 741 <refsect2><title>(type *)talloc_get_type(const void *ptr, type);</title> | |
| 742 <para> | |
| 743 This macro allows you to do type checking on talloc pointers. It | |
| 744 is particularly useful for void* private pointers. It is | |
| 745 equivalent to this: | |
| 746 </para> | |
| 747 <programlisting>(type *)talloc_check_name(ptr, #type)</programlisting> | |
| 748 </refsect2> | |
| 749 <refsect2><title>talloc_set_type(const void *ptr, type);</title> | |
| 750 <para> | |
| 751 This macro allows you to force the name of a pointer to be a | |
| 752 particular <emphasis>type</emphasis>. This can be | |
| 753 used in conjunction with talloc_get_type() to do type checking on | |
| 754 void* pointers. | |
| 755 </para> | |
| 756 <para> | |
| 757 It is equivalent to this: | |
| 758 </para> | |
| 759 <programlisting>talloc_set_name_const(ptr, #type)</programlisting> | |
| 760 </refsect2> | |
| 761 <refsect2><title>talloc_set_log_fn(void (*log_fn)(const char *message));</ti
tle> | |
| 762 <para> | |
| 763 This function sets a logging function that talloc will use for | |
| 764 warnings and errors. By default talloc will not print any warnings or | |
| 765 errors. | |
| 766 </para> | |
| 767 </refsect2> | |
| 768 <refsect2><title>talloc_set_log_stderr(void);</title> | |
| 769 <para> | |
| 770 This sets the talloc log function to write log messages to stderr | |
| 771 </para> | |
| 772 </refsect2> | |
| 773 </refsect1> | |
| 774 <refsect1><title>PERFORMANCE</title> | |
| 775 <para> | |
| 776 All the additional features of talloc(3) over malloc(3) do come at a | |
| 777 price. We have a simple performance test in Samba4 that measures | |
| 778 talloc() versus malloc() performance, and it seems that talloc() is | |
| 779 about 10% slower than malloc() on my x86 Debian Linux box. For | |
| 780 Samba, the great reduction in code complexity that we get by using | |
| 781 talloc makes this worthwhile, especially as the total overhead of | |
| 782 talloc/malloc in Samba is already quite small. | |
| 783 </para> | |
| 784 </refsect1> | |
| 785 <refsect1><title>SEE ALSO</title> | |
| 786 <para> | |
| 787 malloc(3), strndup(3), vasprintf(3), asprintf(3), | |
| 788 <ulink url="http://talloc.samba.org/"/> | |
| 789 </para> | |
| 790 </refsect1> | |
| 791 <refsect1><title>COPYRIGHT/LICENSE</title> | |
| 792 <para> | |
| 793 Copyright (C) Andrew Tridgell 2004 | |
| 794 </para> | |
| 795 <para> | |
| 796 This program is free software; you can redistribute it and/or modify | |
| 797 it under the terms of the GNU General Public License as published by | |
| 798 the Free Software Foundation; either version 3 of the License, or (at | |
| 799 your option) any later version. | |
| 800 </para> | |
| 801 <para> | |
| 802 This program is distributed in the hope that it will be useful, but | |
| 803 WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 804 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 805 General Public License for more details. | |
| 806 </para> | |
| 807 <para> | |
| 808 You should have received a copy of the GNU General Public License | |
| 809 along with this program; if not, see http://www.gnu.org/licenses/. | |
| 810 </para> | |
| 811 </refsect1> | |
| 812 </refentry> | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 2282793002:
Remove unused third_party/talloc (Closed)
