Apache Portable Runtime
 All Data Structures Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
apr_pools.h
Go to the documentation of this file.
1 /* Licensed to the Apache Software Foundation (ASF) under one or more
2  * contributor license agreements. See the NOTICE file distributed with
3  * this work for additional information regarding copyright ownership.
4  * The ASF licenses this file to You under the Apache License, Version 2.0
5  * (the "License"); you may not use this file except in compliance with
6  * the License. You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef APR_POOLS_H
18 #define APR_POOLS_H
19 
20 /**
21  * @file apr_pools.h
22  * @brief APR memory allocation
23  *
24  * Resource allocation routines...
25  *
26  * designed so that we don't have to keep track of EVERYTHING so that
27  * it can be explicitly freed later (a fundamentally unsound strategy ---
28  * particularly in the presence of die()).
29  *
30  * Instead, we maintain pools, and allocate items (both memory and I/O
31  * handlers) from the pools --- currently there are two, one for
32  * per-transaction info, and one for config info. When a transaction is
33  * over, we can delete everything in the per-transaction apr_pool_t without
34  * fear, and without thinking too hard about it either.
35  *
36  * Note that most operations on pools are not thread-safe: a single pool
37  * should only be accessed by a single thread at any given time. The one
38  * exception to this rule is creating a subpool of a given pool: one or more
39  * threads can safely create subpools at the same time that another thread
40  * accesses the parent pool.
41  */
42 
43 #include "apr.h"
44 #include "apr_errno.h"
45 #include "apr_general.h" /* for APR_STRINGIFY */
46 #define APR_WANT_MEMFUNC /**< for no good reason? */
47 #include "apr_want.h"
48 
49 #ifdef __cplusplus
50 extern "C" {
51 #endif
52 
53 /**
54  * @defgroup apr_pools Memory Pool Functions
55  * @ingroup APR
56  * @{
57  */
58 
59 /** The fundamental pool type */
60 typedef struct apr_pool_t apr_pool_t;
61 
62 
63 /**
64  * Declaration helper macro to construct apr_foo_pool_get()s.
65  *
66  * This standardized macro is used by opaque (APR) data types to return
67  * the apr_pool_t that is associated with the data type.
68  *
69  * APR_POOL_DECLARE_ACCESSOR() is used in a header file to declare the
70  * accessor function. A typical usage and result would be:
71  * <pre>
72  * APR_POOL_DECLARE_ACCESSOR(file);
73  * becomes:
74  * APR_DECLARE(apr_pool_t *) apr_file_pool_get(apr_file_t *ob);
75  * </pre>
76  * @remark Doxygen unwraps this macro (via doxygen.conf) to provide
77  * actual help for each specific occurance of apr_foo_pool_get.
78  * @remark the linkage is specified for APR. It would be possible to expand
79  * the macros to support other linkages.
80  */
81 #define APR_POOL_DECLARE_ACCESSOR(type) \
82  APR_DECLARE(apr_pool_t *) apr_##type##_pool_get \
83  (const apr_##type##_t *the##type)
84 
85 /**
86  * Implementation helper macro to provide apr_foo_pool_get()s.
87  *
88  * In the implementation, the APR_POOL_IMPLEMENT_ACCESSOR() is used to
89  * actually define the function. It assumes the field is named "pool".
90  */
91 #define APR_POOL_IMPLEMENT_ACCESSOR(type) \
92  APR_DECLARE(apr_pool_t *) apr_##type##_pool_get \
93  (const apr_##type##_t *the##type) \
94  { return the##type->pool; }
95 
96 
97 /**
98  * Pool debug levels
99  *
100  * <pre>
101  * | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
102  * ---------------------------------
103  * | | | | | | | | x | General debug code enabled (useful in
104  * combination with --with-efence).
105  *
106  * | | | | | | | x | | Verbose output on stderr (report
107  * CREATE, CLEAR, DESTROY).
108  *
109  * | | | | x | | | | | Verbose output on stderr (report
110  * PALLOC, PCALLOC).
111  *
112  * | | | | | | x | | | Lifetime checking. On each use of a
113  * pool, check its lifetime. If the pool
114  * is out of scope, abort().
115  * In combination with the verbose flag
116  * above, it will output LIFE in such an
117  * event prior to aborting.
118  *
119  * | | | | | x | | | | Pool owner checking. On each use of a
120  * pool, check if the current thread is the
121  * pools owner. If not, abort(). In
122  * combination with the verbose flag above,
123  * it will output OWNER in such an event
124  * prior to aborting. Use the debug
125  * function apr_pool_owner_set() to switch
126  * a pools ownership.
127  *
128  * When no debug level was specified, assume general debug mode.
129  * If level 0 was specified, debugging is switched off
130  * </pre>
131  */
132 #if defined(APR_POOL_DEBUG)
133 /* If APR_POOL_DEBUG is blank, we get 1; if it is a number, we get -1. */
134 #if (APR_POOL_DEBUG - APR_POOL_DEBUG -1 == 1)
135 #undef APR_POOL_DEBUG
136 #define APR_POOL_DEBUG 1
137 #endif
138 #else
139 #define APR_POOL_DEBUG 0
140 #endif
141 
142 /** the place in the code where the particular function was called */
143 #define APR_POOL__FILE_LINE__ __FILE__ ":" APR_STRINGIFY(__LINE__)
144 
145 
146 
147 /** A function that is called when allocation fails. */
148 typedef int (*apr_abortfunc_t)(int retcode);
149 
150 /*
151  * APR memory structure manipulators (pools, tables, and arrays).
152  */
153 
154 /*
155  * Initialization
156  */
157 
158 /**
159  * Setup all of the internal structures required to use pools
160  * @remark Programs do NOT need to call this directly. APR will call this
161  * automatically from apr_initialize.
162  * @internal
163  */
165 
166 /**
167  * Tear down all of the internal structures required to use pools
168  * @remark Programs do NOT need to call this directly. APR will call this
169  * automatically from apr_terminate.
170  * @internal
171  */
172 APR_DECLARE(void) apr_pool_terminate(void);
173 
174 
175 /*
176  * Pool creation/destruction
177  */
178 
179 #include "apr_allocator.h"
180 
181 /**
182  * Create a new pool.
183  * @param newpool The pool we have just created.
184  * @param parent The parent pool. If this is NULL, the new pool is a root
185  * pool. If it is non-NULL, the new pool will inherit all
186  * of its parent pool's attributes, except the apr_pool_t will
187  * be a sub-pool.
188  * @param abort_fn A function to use if the pool cannot allocate more memory.
189  * @param allocator The allocator to use with the new pool. If NULL the
190  * allocator of the parent pool will be used.
191  * @remark This function is thread-safe, in the sense that multiple threads
192  * can safely create subpools of the same parent pool concurrently.
193  * Similarly, a subpool can be created by one thread at the same
194  * time that another thread accesses the parent pool.
195  */
197  apr_pool_t *parent,
198  apr_abortfunc_t abort_fn,
199  apr_allocator_t *allocator);
200 
201 /**
202  * Create a new pool.
203  * @deprecated @see apr_pool_create_unmanaged_ex.
204  */
206  apr_abortfunc_t abort_fn,
207  apr_allocator_t *allocator);
208 
209 /**
210  * Create a new unmanaged pool.
211  * @param newpool The pool we have just created.
212  * @param abort_fn A function to use if the pool cannot allocate more memory.
213  * @param allocator The allocator to use with the new pool. If NULL a
214  * new allocator will be crated with newpool as owner.
215  * @remark An unmanaged pool is a special pool without a parent; it will
216  * NOT be destroyed upon apr_terminate. It must be explicitly
217  * destroyed by calling apr_pool_destroy, to prevent memory leaks.
218  * Use of this function is discouraged, think twice about whether
219  * you really really need it.
220  */
222  apr_abortfunc_t abort_fn,
223  apr_allocator_t *allocator);
224 
225 /**
226  * Debug version of apr_pool_create_ex.
227  * @param newpool @see apr_pool_create.
228  * @param parent @see apr_pool_create.
229  * @param abort_fn @see apr_pool_create.
230  * @param allocator @see apr_pool_create.
231  * @param file_line Where the function is called from.
232  * This is usually APR_POOL__FILE_LINE__.
233  * @remark Only available when APR_POOL_DEBUG is defined.
234  * Call this directly if you have you apr_pool_create_ex
235  * calls in a wrapper function and wish to override
236  * the file_line argument to reflect the caller of
237  * your wrapper function. If you do not have
238  * apr_pool_create_ex in a wrapper, trust the macro
239  * and don't call apr_pool_create_ex_debug directly.
240  */
242  apr_pool_t *parent,
243  apr_abortfunc_t abort_fn,
244  apr_allocator_t *allocator,
245  const char *file_line);
246 
247 #if APR_POOL_DEBUG
248 #define apr_pool_create_ex(newpool, parent, abort_fn, allocator) \
249  apr_pool_create_ex_debug(newpool, parent, abort_fn, allocator, \
250  APR_POOL__FILE_LINE__)
251 #endif
252 
253 /**
254  * Debug version of apr_pool_create_core_ex.
255  * @deprecated @see apr_pool_create_unmanaged_ex_debug.
256  */
258  apr_abortfunc_t abort_fn,
259  apr_allocator_t *allocator,
260  const char *file_line);
261 
262 /**
263  * Debug version of apr_pool_create_unmanaged_ex.
264  * @param newpool @see apr_pool_create_unmanaged.
265  * @param abort_fn @see apr_pool_create_unmanaged.
266  * @param allocator @see apr_pool_create_unmanaged.
267  * @param file_line Where the function is called from.
268  * This is usually APR_POOL__FILE_LINE__.
269  * @remark Only available when APR_POOL_DEBUG is defined.
270  * Call this directly if you have you apr_pool_create_unmanaged_ex
271  * calls in a wrapper function and wish to override
272  * the file_line argument to reflect the caller of
273  * your wrapper function. If you do not have
274  * apr_pool_create_core_ex in a wrapper, trust the macro
275  * and don't call apr_pool_create_core_ex_debug directly.
276  */
278  apr_abortfunc_t abort_fn,
279  apr_allocator_t *allocator,
280  const char *file_line);
281 
282 #if APR_POOL_DEBUG
283 #define apr_pool_create_core_ex(newpool, abort_fn, allocator) \
284  apr_pool_create_unmanaged_ex_debug(newpool, abort_fn, allocator, \
285  APR_POOL__FILE_LINE__)
286 
287 #define apr_pool_create_unmanaged_ex(newpool, abort_fn, allocator) \
288  apr_pool_create_unmanaged_ex_debug(newpool, abort_fn, allocator, \
289  APR_POOL__FILE_LINE__)
290 
291 #endif
292 
293 /**
294  * Create a new pool.
295  * @param newpool The pool we have just created.
296  * @param parent The parent pool. If this is NULL, the new pool is a root
297  * pool. If it is non-NULL, the new pool will inherit all
298  * of its parent pool's attributes, except the apr_pool_t will
299  * be a sub-pool.
300  * @remark This function is thread-safe, in the sense that multiple threads
301  * can safely create subpools of the same parent pool concurrently.
302  * Similarly, a subpool can be created by one thread at the same
303  * time that another thread accesses the parent pool.
304  */
305 #if defined(DOXYGEN)
307  apr_pool_t *parent);
308 #else
309 #if APR_POOL_DEBUG
310 #define apr_pool_create(newpool, parent) \
311  apr_pool_create_ex_debug(newpool, parent, NULL, NULL, \
312  APR_POOL__FILE_LINE__)
313 #else
314 #define apr_pool_create(newpool, parent) \
315  apr_pool_create_ex(newpool, parent, NULL, NULL)
316 #endif
317 #endif
318 
319 /**
320  * Create a new pool.
321  * @param newpool The pool we have just created.
322  */
323 #if defined(DOXYGEN)
325 APR_DECLARE(apr_status_t) apr_pool_create_unmanaged(apr_pool_t **newpool);
326 #else
327 #if APR_POOL_DEBUG
328 #define apr_pool_create_core(newpool) \
329  apr_pool_create_unmanaged_ex_debug(newpool, NULL, NULL, \
330  APR_POOL__FILE_LINE__)
331 #define apr_pool_create_unmanaged(newpool) \
332  apr_pool_create_unmanaged_ex_debug(newpool, NULL, NULL, \
333  APR_POOL__FILE_LINE__)
334 #else
335 #define apr_pool_create_core(newpool) \
336  apr_pool_create_unmanaged_ex(newpool, NULL, NULL)
337 #define apr_pool_create_unmanaged(newpool) \
338  apr_pool_create_unmanaged_ex(newpool, NULL, NULL)
339 #endif
340 #endif
341 
342 /**
343  * Find the pool's allocator
344  * @param pool The pool to get the allocator from.
345  */
347 
348 /**
349  * Clear all memory in the pool and run all the cleanups. This also destroys all
350  * subpools.
351  * @param p The pool to clear
352  * @remark This does not actually free the memory, it just allows the pool
353  * to re-use this memory for the next allocation.
354  * @see apr_pool_destroy()
355  */
357 
358 /**
359  * Debug version of apr_pool_clear.
360  * @param p See: apr_pool_clear.
361  * @param file_line Where the function is called from.
362  * This is usually APR_POOL__FILE_LINE__.
363  * @remark Only available when APR_POOL_DEBUG is defined.
364  * Call this directly if you have you apr_pool_clear
365  * calls in a wrapper function and wish to override
366  * the file_line argument to reflect the caller of
367  * your wrapper function. If you do not have
368  * apr_pool_clear in a wrapper, trust the macro
369  * and don't call apr_pool_destroy_clear directly.
370  */
372  const char *file_line);
373 
374 #if APR_POOL_DEBUG
375 #define apr_pool_clear(p) \
376  apr_pool_clear_debug(p, APR_POOL__FILE_LINE__)
377 #endif
378 
379 /**
380  * Destroy the pool. This takes similar action as apr_pool_clear() and then
381  * frees all the memory.
382  * @param p The pool to destroy
383  * @remark This will actually free the memory
384  */
386 
387 /**
388  * Debug version of apr_pool_destroy.
389  * @param p See: apr_pool_destroy.
390  * @param file_line Where the function is called from.
391  * This is usually APR_POOL__FILE_LINE__.
392  * @remark Only available when APR_POOL_DEBUG is defined.
393  * Call this directly if you have you apr_pool_destroy
394  * calls in a wrapper function and wish to override
395  * the file_line argument to reflect the caller of
396  * your wrapper function. If you do not have
397  * apr_pool_destroy in a wrapper, trust the macro
398  * and don't call apr_pool_destroy_debug directly.
399  */
401  const char *file_line);
402 
403 #if APR_POOL_DEBUG
404 #define apr_pool_destroy(p) \
405  apr_pool_destroy_debug(p, APR_POOL__FILE_LINE__)
406 #endif
407 
408 
409 /*
410  * Memory allocation
411  */
412 
413 /**
414  * Allocate a block of memory from a pool
415  * @param p The pool to allocate from
416  * @param size The amount of memory to allocate
417  * @return The allocated memory
418  */
419 APR_DECLARE(void *) apr_palloc(apr_pool_t *p, apr_size_t size);
420 
421 /**
422  * Debug version of apr_palloc
423  * @param p See: apr_palloc
424  * @param size See: apr_palloc
425  * @param file_line Where the function is called from.
426  * This is usually APR_POOL__FILE_LINE__.
427  * @return See: apr_palloc
428  */
429 APR_DECLARE(void *) apr_palloc_debug(apr_pool_t *p, apr_size_t size,
430  const char *file_line);
431 
432 #if APR_POOL_DEBUG
433 #define apr_palloc(p, size) \
434  apr_palloc_debug(p, size, APR_POOL__FILE_LINE__)
435 #endif
436 
437 /**
438  * Allocate a block of memory from a pool and set all of the memory to 0
439  * @param p The pool to allocate from
440  * @param size The amount of memory to allocate
441  * @return The allocated memory
442  */
443 #if defined(DOXYGEN)
444 APR_DECLARE(void *) apr_pcalloc(apr_pool_t *p, apr_size_t size);
445 #elif !APR_POOL_DEBUG
446 #define apr_pcalloc(p, size) memset(apr_palloc(p, size), 0, size)
447 #endif
448 
449 /**
450  * Debug version of apr_pcalloc
451  * @param p See: apr_pcalloc
452  * @param size See: apr_pcalloc
453  * @param file_line Where the function is called from.
454  * This is usually APR_POOL__FILE_LINE__.
455  * @return See: apr_pcalloc
456  */
457 APR_DECLARE(void *) apr_pcalloc_debug(apr_pool_t *p, apr_size_t size,
458  const char *file_line);
459 
460 #if APR_POOL_DEBUG
461 #define apr_pcalloc(p, size) \
462  apr_pcalloc_debug(p, size, APR_POOL__FILE_LINE__)
463 #endif
464 
465 
466 /*
467  * Pool Properties
468  */
469 
470 /**
471  * Set the function to be called when an allocation failure occurs.
472  * @remark If the program wants APR to exit on a memory allocation error,
473  * then this function can be called to set the callback to use (for
474  * performing cleanup and then exiting). If this function is not called,
475  * then APR will return an error and expect the calling program to
476  * deal with the error accordingly.
477  */
479  apr_pool_t *pool);
480 
481 /**
482  * Get the abort function associated with the specified pool.
483  * @param pool The pool for retrieving the abort function.
484  * @return The abort function for the given pool.
485  */
487 
488 /**
489  * Get the parent pool of the specified pool.
490  * @param pool The pool for retrieving the parent pool.
491  * @return The parent of the given pool.
492  */
494 
495 /**
496  * Determine if pool a is an ancestor of pool b.
497  * @param a The pool to search
498  * @param b The pool to search for
499  * @return True if a is an ancestor of b, NULL is considered an ancestor
500  * of all pools.
501  * @remark if compiled with APR_POOL_DEBUG, this function will also
502  * return true if A is a pool which has been guaranteed by the caller
503  * (using apr_pool_join) to have a lifetime at least as long as some
504  * ancestor of pool B.
505  */
507 
508 /**
509  * Tag a pool (give it a name)
510  * @param pool The pool to tag
511  * @param tag The tag
512  */
513 APR_DECLARE(void) apr_pool_tag(apr_pool_t *pool, const char *tag);
514 
515 
516 /*
517  * User data management
518  */
519 
520 /**
521  * Set the data associated with the current pool
522  * @param data The user data associated with the pool.
523  * @param key The key to use for association
524  * @param cleanup The cleanup program to use to cleanup the data (NULL if none)
525  * @param pool The current pool
526  * @warning The data to be attached to the pool should have a life span
527  * at least as long as the pool it is being attached to.
528  *
529  * Users of APR must take EXTREME care when choosing a key to
530  * use for their data. It is possible to accidentally overwrite
531  * data by choosing a key that another part of the program is using.
532  * Therefore it is advised that steps are taken to ensure that unique
533  * keys are used for all of the userdata objects in a particular pool
534  * (the same key in two different pools or a pool and one of its
535  * subpools is okay) at all times. Careful namespace prefixing of
536  * key names is a typical way to help ensure this uniqueness.
537  *
538  */
540  const void *data,
541  const char *key,
542  apr_status_t (*cleanup)(void *),
543  apr_pool_t *pool);
544 
545 /**
546  * Set the data associated with the current pool
547  * @param data The user data associated with the pool.
548  * @param key The key to use for association
549  * @param cleanup The cleanup program to use to cleanup the data (NULL if none)
550  * @param pool The current pool
551  * @note same as apr_pool_userdata_set(), except that this version doesn't
552  * make a copy of the key (this function is useful, for example, when
553  * the key is a string literal)
554  * @warning This should NOT be used if the key could change addresses by
555  * any means between the apr_pool_userdata_setn() call and a
556  * subsequent apr_pool_userdata_get() on that key, such as if a
557  * static string is used as a userdata key in a DSO and the DSO could
558  * be unloaded and reloaded between the _setn() and the _get(). You
559  * MUST use apr_pool_userdata_set() in such cases.
560  * @warning More generally, the key and the data to be attached to the
561  * pool should have a life span at least as long as the pool itself.
562  *
563  */
565  const void *data,
566  const char *key,
567  apr_status_t (*cleanup)(void *),
568  apr_pool_t *pool);
569 
570 /**
571  * Return the data associated with the current pool.
572  * @param data The user data associated with the pool.
573  * @param key The key for the data to retrieve
574  * @param pool The current pool.
575  */
576 APR_DECLARE(apr_status_t) apr_pool_userdata_get(void **data, const char *key,
577  apr_pool_t *pool);
578 
579 
580 /**
581  * @defgroup PoolCleanup Pool Cleanup Functions
582  *
583  * Cleanups are performed in the reverse order they were registered. That is:
584  * Last In, First Out. A cleanup function can safely allocate memory from
585  * the pool that is being cleaned up. It can also safely register additional
586  * cleanups which will be run LIFO, directly after the current cleanup
587  * terminates. Cleanups have to take caution in calling functions that
588  * create subpools. Subpools, created during cleanup will NOT automatically
589  * be cleaned up. In other words, cleanups are to clean up after themselves.
590  *
591  * @{
592  */
593 
594 /**
595  * Register a function to be called when a pool is cleared or destroyed
596  * @param p The pool register the cleanup with
597  * @param data The data to pass to the cleanup function.
598  * @param plain_cleanup The function to call when the pool is cleared
599  * or destroyed
600  * @param child_cleanup The function to call when a child process is about
601  * to exec - this function is called in the child, obviously!
602  */
604  apr_pool_t *p,
605  const void *data,
606  apr_status_t (*plain_cleanup)(void *),
607  apr_status_t (*child_cleanup)(void *));
608 
609 /**
610  * Register a function to be called when a pool is cleared or destroyed.
611  *
612  * Unlike apr_pool_cleanup_register which register a cleanup
613  * that is called AFTER all subpools are destroyed this function register
614  * a function that will be called before any of the subpool is destoryed.
615  *
616  * @param p The pool register the cleanup with
617  * @param data The data to pass to the cleanup function.
618  * @param plain_cleanup The function to call when the pool is cleared
619  * or destroyed
620  */
622  apr_pool_t *p,
623  const void *data,
624  apr_status_t (*plain_cleanup)(void *));
625 
626 /**
627  * Remove a previously registered cleanup function.
628  *
629  * The cleanup most recently registered with @a p having the same values of
630  * @a data and @a cleanup will be removed.
631  *
632  * @param p The pool to remove the cleanup from
633  * @param data The data of the registered cleanup
634  * @param cleanup The function to remove from cleanup
635  * @remarks For some strange reason only the plain_cleanup is handled by this
636  * function
637  */
638 APR_DECLARE(void) apr_pool_cleanup_kill(apr_pool_t *p, const void *data,
639  apr_status_t (*cleanup)(void *));
640 
641 /**
642  * Replace the child cleanup function of a previously registered cleanup.
643  *
644  * The cleanup most recently registered with @a p having the same values of
645  * @a data and @a plain_cleanup will have the registered child cleanup
646  * function replaced with @a child_cleanup.
647  *
648  * @param p The pool of the registered cleanup
649  * @param data The data of the registered cleanup
650  * @param plain_cleanup The plain cleanup function of the registered cleanup
651  * @param child_cleanup The function to register as the child cleanup
652  */
654  apr_pool_t *p,
655  const void *data,
656  apr_status_t (*plain_cleanup)(void *),
657  apr_status_t (*child_cleanup)(void *));
658 
659 /**
660  * Run the specified cleanup function immediately and unregister it.
661  *
662  * The cleanup most recently registered with @a p having the same values of
663  * @a data and @a cleanup will be removed and @a cleanup will be called
664  * with @a data as the argument.
665  *
666  * @param p The pool to remove the cleanup from
667  * @param data The data to remove from cleanup
668  * @param cleanup The function to remove from cleanup
669  */
671  apr_pool_t *p,
672  void *data,
673  apr_status_t (*cleanup)(void *));
674 
675 /**
676  * An empty cleanup function.
677  *
678  * Passed to apr_pool_cleanup_register() when no cleanup is required.
679  *
680  * @param data The data to cleanup, will not be used by this function.
681  */
683 
684 /**
685  * Run all registered child cleanups, in preparation for an exec()
686  * call in a forked child -- close files, etc., but *don't* flush I/O
687  * buffers, *don't* wait for subprocesses, and *don't* free any
688  * memory.
689  */
691 
692 /** @} */
693 
694 /**
695  * @defgroup PoolDebug Pool Debugging functions.
696  *
697  * pools have nested lifetimes -- sub_pools are destroyed when the
698  * parent pool is cleared. We allow certain liberties with operations
699  * on things such as tables (and on other structures in a more general
700  * sense) where we allow the caller to insert values into a table which
701  * were not allocated from the table's pool. The table's data will
702  * remain valid as long as all the pools from which its values are
703  * allocated remain valid.
704  *
705  * For example, if B is a sub pool of A, and you build a table T in
706  * pool B, then it's safe to insert data allocated in A or B into T
707  * (because B lives at most as long as A does, and T is destroyed when
708  * B is cleared/destroyed). On the other hand, if S is a table in
709  * pool A, it is safe to insert data allocated in A into S, but it
710  * is *not safe* to insert data allocated from B into S... because
711  * B can be cleared/destroyed before A is (which would leave dangling
712  * pointers in T's data structures).
713  *
714  * In general we say that it is safe to insert data into a table T
715  * if the data is allocated in any ancestor of T's pool. This is the
716  * basis on which the APR_POOL_DEBUG code works -- it tests these ancestor
717  * relationships for all data inserted into tables. APR_POOL_DEBUG also
718  * provides tools (apr_pool_find, and apr_pool_is_ancestor) for other
719  * folks to implement similar restrictions for their own data
720  * structures.
721  *
722  * However, sometimes this ancestor requirement is inconvenient --
723  * sometimes it's necessary to create a sub pool where the sub pool is
724  * guaranteed to have the same lifetime as the parent pool. This is a
725  * guarantee implemented by the *caller*, not by the pool code. That
726  * is, the caller guarantees they won't destroy the sub pool
727  * individually prior to destroying the parent pool.
728  *
729  * In this case the caller must call apr_pool_join() to indicate this
730  * guarantee to the APR_POOL_DEBUG code.
731  *
732  * These functions are only implemented when #APR_POOL_DEBUG is set.
733  *
734  * @{
735  */
736 #if APR_POOL_DEBUG || defined(DOXYGEN)
737 /**
738  * Guarantee that a subpool has the same lifetime as the parent.
739  * @param p The parent pool
740  * @param sub The subpool
741  */
743 
744 /**
745  * Find a pool from something allocated in it.
746  * @param mem The thing allocated in the pool
747  * @return The pool it is allocated in
748  */
749 APR_DECLARE(apr_pool_t *) apr_pool_find(const void *mem);
750 
751 /**
752  * Report the number of bytes currently in the pool
753  * @param p The pool to inspect
754  * @param recurse Recurse/include the subpools' sizes
755  * @return The number of bytes
756  */
757 APR_DECLARE(apr_size_t) apr_pool_num_bytes(apr_pool_t *p, int recurse);
758 
759 /**
760  * Lock a pool
761  * @param pool The pool to lock
762  * @param flag The flag
763  */
764 APR_DECLARE(void) apr_pool_lock(apr_pool_t *pool, int flag);
765 
766 /* @} */
767 
768 #else /* APR_POOL_DEBUG or DOXYGEN */
769 
770 #ifdef apr_pool_join
771 #undef apr_pool_join
772 #endif
773 #define apr_pool_join(a,b)
774 
775 #ifdef apr_pool_lock
776 #undef apr_pool_lock
777 #endif
778 #define apr_pool_lock(pool, lock)
779 
780 #endif /* APR_POOL_DEBUG or DOXYGEN */
781 
782 /** @} */
783 
784 #ifdef __cplusplus
785 }
786 #endif
787 
788 #endif /* !APR_POOLS_H */