Memory Pool Functions

Modules
	Pool Cleanup Functions
	Pool Debugging functions.

Macros
#define	APR_POOL_DECLARE_ACCESSOR(type)
#define	APR_POOL_IMPLEMENT_ACCESSOR(type)
#define	APR_POOL__FILE_LINE__   __FILE__ ":" APR_STRINGIFY(__LINE__)

Typedefs
typedef struct apr_pool_t	apr_pool_t
typedef int(*	apr_abortfunc_t) (int retcode)

Functions
apr_status_t	apr_pool_initialize (void)
void	apr_pool_terminate (void)
apr_status_t	apr_pool_create_ex (apr_pool_t **newpool, apr_pool_t *parent, apr_abortfunc_t abort_fn, apr_allocator_t *allocator)
apr_status_t	apr_pool_create_unmanaged_ex (apr_pool_t **newpool, apr_abortfunc_t abort_fn, apr_allocator_t *allocator)
apr_status_t	apr_pool_create_ex_debug (apr_pool_t **newpool, apr_pool_t *parent, apr_abortfunc_t abort_fn, apr_allocator_t *allocator, const char *file_line)
apr_status_t	apr_pool_create_unmanaged_ex_debug (apr_pool_t **newpool, apr_abortfunc_t abort_fn, apr_allocator_t *allocator, const char *file_line)
apr_status_t	apr_pool_create (apr_pool_t **newpool, apr_pool_t *parent)
apr_status_t	apr_pool_create_unmanaged (apr_pool_t **newpool)
apr_allocator_t *	apr_pool_allocator_get (apr_pool_t *pool)
void	apr_pool_clear (apr_pool_t *p)
void	apr_pool_clear_debug (apr_pool_t *p, const char *file_line)
void	apr_pool_destroy (apr_pool_t *p)
void	apr_pool_destroy_debug (apr_pool_t *p, const char *file_line)
void *	apr_palloc (apr_pool_t *p, apr_size_t size)
void *	apr_palloc_debug (apr_pool_t *p, apr_size_t size, const char *file_line)
void *	apr_pcalloc (apr_pool_t *p, apr_size_t size)
void *	apr_pcalloc_debug (apr_pool_t *p, apr_size_t size, const char *file_line)
void	apr_pool_abort_set (apr_abortfunc_t abortfunc, apr_pool_t *pool)
apr_abortfunc_t	apr_pool_abort_get (apr_pool_t *pool)
apr_pool_t *	apr_pool_parent_get (apr_pool_t *pool)
int	apr_pool_is_ancestor (apr_pool_t *a, apr_pool_t *b)
void	apr_pool_tag (apr_pool_t *pool, const char *tag)
apr_status_t	apr_pool_userdata_set (const void *data, const char *key, apr_status_t(*cleanup)(void *), apr_pool_t *pool)
apr_status_t	apr_pool_userdata_setn (const void *data, const char *key, apr_status_t(*cleanup)(void *), apr_pool_t *pool)
apr_status_t	apr_pool_userdata_get (void **data, const char *key, apr_pool_t *pool)

Detailed Description

Macro Definition Documentation

#define APR_POOL__FILE_LINE__   __FILE__ ":" APR_STRINGIFY(__LINE__)

Pool debug levels

| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |

|   |   |   |   |   |   |   | x |  General debug code enabled (useful in
                                   combination with –with-efence).

|   |   |   |   |   |   | x |   |  Verbose output on stderr (report
                                   CREATE, CLEAR, DESTROY).

|   |   |   | x |   |   |   |   |  Verbose output on stderr (report
                                   PALLOC, PCALLOC).

|   |   |   |   |   | x |   |   |  Lifetime checking. On each use of a
                                   pool, check its lifetime.  If the pool
                                   is out of scope, abort().
                                   In combination with the verbose flag
                                   above, it will output LIFE in such an
                                   event prior to aborting.

|   |   |   |   | x |   |   |   |  Pool owner checking.  On each use of a
                                   pool, check if the current thread is the
                                   pool's owner.  If not, abort().  In
                                   combination with the verbose flag above,
                                   it will output OWNER in such an event
                                   prior to aborting.  Use the debug
                                   function apr_pool_owner_set() to switch
                                   a pool's ownership.

When no debug level was specified, assume general debug mode.
If level 0 was specified, debugging is switched off.

the place in the code where the particular function was called

#define APR_POOL_DECLARE_ACCESSOR

(

type

)

Value:

APR_DECLARE(apr_pool_t *) apr_##type##_pool_get \
        (const apr_##type##_t *the##type)

Declaration helper macro to construct apr_foo_pool_get()s.

This standardized macro is used by opaque (APR) data types to return the apr_pool_t that is associated with the data type.

APR_POOL_DECLARE_ACCESSOR() is used in a header file to declare the accessor function. A typical usage and result would be:

   APR_POOL_DECLARE_ACCESSOR(file);
becomes:
   APR_DECLARE(apr_pool_t *) apr_file_pool_get(const apr_file_t *thefile);

Remarks

Doxygen unwraps this macro (via doxygen.conf) to provide actual help for each specific occurrence of apr_foo_pool_get.

the linkage is specified for APR. It would be possible to expand the macros to support other linkages.

#define APR_POOL_IMPLEMENT_ACCESSOR

(

type

)

Value:

APR_DECLARE(apr_pool_t *) apr_##type##_pool_get \
            (const apr_##type##_t *the##type) \
        { return the##type->pool; }

Implementation helper macro to provide apr_foo_pool_get()s.

In the implementation, the APR_POOL_IMPLEMENT_ACCESSOR() is used to actually define the function. It assumes the field is named "pool".

Typedef Documentation

typedef int(* apr_abortfunc_t) (int retcode)

A function that is called when allocation fails.

typedef struct apr_pool_t apr_pool_t

The fundamental pool type

Function Documentation

void* apr_palloc	(	apr_pool_t *	p,
		apr_size_t	size
	)

Allocate a block of memory from a pool

Parameters

p	The pool to allocate from
size	The amount of memory to allocate

Returns

The allocated memory

void* apr_palloc_debug	(	apr_pool_t *	p,
		apr_size_t	size,
		const char *	file_line
	)

Debug version of apr_palloc

Parameters

p	See: apr_palloc
size	See: apr_palloc
file_line	Where the function is called from. This is usually APR_POOL__FILE_LINE__.

Returns

See: apr_palloc

void* apr_pcalloc	(	apr_pool_t *	p,
		apr_size_t	size
	)

Allocate a block of memory from a pool and set all of the memory to 0

Parameters

p	The pool to allocate from
size	The amount of memory to allocate

Returns

The allocated memory

void* apr_pcalloc_debug	(	apr_pool_t *	p,
		apr_size_t	size,
		const char *	file_line
	)

Debug version of apr_pcalloc

Parameters

p	See: apr_pcalloc
size	See: apr_pcalloc
file_line	Where the function is called from. This is usually APR_POOL__FILE_LINE__.

Returns

See: apr_pcalloc

apr_abortfunc_t apr_pool_abort_get

(

apr_pool_t *

pool

)

Get the abort function associated with the specified pool.

Parameters

pool	The pool for retrieving the abort function.

Returns

The abort function for the given pool.

void apr_pool_abort_set	(	apr_abortfunc_t	abortfunc,
		apr_pool_t *	pool
	)

Set the function to be called when an allocation failure occurs.

Remarks

If the program wants APR to exit on a memory allocation error, then this function can be called to set the callback to use (for performing cleanup and then exiting). If this function is not called, then APR will return an error and expect the calling program to deal with the error accordingly.

apr_allocator_t* apr_pool_allocator_get

(

apr_pool_t *

pool

)

Find the pool's allocator

Parameters

pool	The pool to get the allocator from.

void apr_pool_clear

(

apr_pool_t *

p

)

Clear all memory in the pool and run all the cleanups. This also destroys all subpools.

Parameters

p	The pool to clear

Remarks

This does not actually free the memory, it just allows the pool to re-use this memory for the next allocation.

See also

apr_pool_destroy()

void apr_pool_clear_debug	(	apr_pool_t *	p,
		const char *	file_line
	)

Debug version of apr_pool_clear.

Parameters

p	See: apr_pool_clear.
file_line	Where the function is called from. This is usually APR_POOL__FILE_LINE__.

Remarks

Only available when APR_POOL_DEBUG is defined. Call this directly if you have your apr_pool_clear calls in a wrapper function and wish to override the file_line argument to reflect the caller of your wrapper function. If you do not have apr_pool_clear in a wrapper, trust the macro and don't call apr_pool_destroy_clear directly.

apr_status_t apr_pool_create	(	apr_pool_t **	newpool,
		apr_pool_t *	parent
	)

Create a new pool.

Parameters

newpool	The pool we have just created.
parent	The parent pool. If this is NULL, the new pool is a root pool. If it is non-NULL, the new pool will inherit all of its parent pool's attributes, except the apr_pool_t will be a sub-pool.

Remarks

This function is thread-safe, in the sense that multiple threads can safely create subpools of the same parent pool concurrently. Similarly, a subpool can be created by one thread at the same time that another thread accesses the parent pool.

apr_status_t apr_pool_create_ex	(	apr_pool_t **	newpool,
		apr_pool_t *	parent,
		apr_abortfunc_t	abort_fn,
		apr_allocator_t *	allocator
	)

Create a new pool.

Parameters

newpool	The pool we have just created.
parent	The parent pool. If this is NULL, the new pool is a root pool. If it is non-NULL, the new pool will inherit all of its parent pool's attributes, except the apr_pool_t will be a sub-pool.
abort_fn	A function to use if the pool cannot allocate more memory.
allocator	The allocator to use with the new pool. If NULL the allocator of the parent pool will be used.

Remarks

This function is thread-safe, in the sense that multiple threads can safely create subpools of the same parent pool concurrently. Similarly, a subpool can be created by one thread at the same time that another thread accesses the parent pool.

apr_status_t apr_pool_create_ex_debug	(	apr_pool_t **	newpool,
		apr_pool_t *	parent,
		apr_abortfunc_t	abort_fn,
		apr_allocator_t *	allocator,
		const char *	file_line
	)

Debug version of apr_pool_create_ex.

Parameters

newpool

See also

apr_pool_create.

Parameters

parent

See also

apr_pool_create.

Parameters

abort_fn

See also

apr_pool_create.

Parameters

allocator

See also

apr_pool_create.

Parameters

file_line

Where the function is called from. This is usually APR_POOL__FILE_LINE__.

Remarks

Only available when APR_POOL_DEBUG is defined. Call this directly if you have your apr_pool_create_ex calls in a wrapper function and wish to override the file_line argument to reflect the caller of your wrapper function. If you do not have apr_pool_create_ex in a wrapper, trust the macro and don't call apr_pool_create_ex_debug directly.

apr_status_t apr_pool_create_unmanaged

(

apr_pool_t **

newpool

)

Create a new unmanaged pool.

Parameters

newpool

The pool we have just created.

apr_status_t apr_pool_create_unmanaged_ex	(	apr_pool_t **	newpool,
		apr_abortfunc_t	abort_fn,
		apr_allocator_t *	allocator
	)

Create a new unmanaged pool.

Parameters

newpool	The pool we have just created.
abort_fn	A function to use if the pool cannot allocate more memory.
allocator	The allocator to use with the new pool. If NULL a new allocator will be created with the new pool as owner.

Remarks

An unmanaged pool is a special pool without a parent; it will NOT be destroyed upon apr_terminate. It must be explicitly destroyed by calling apr_pool_destroy, to prevent memory leaks. Use of this function is discouraged, think twice about whether you really really need it.

Warning

Any child cleanups registered against the new pool, or against sub-pools thereof, will not be executed during an invocation of apr_proc_create(), so resources created in an "unmanaged" pool hierarchy will leak to child processes.

apr_status_t apr_pool_create_unmanaged_ex_debug	(	apr_pool_t **	newpool,
		apr_abortfunc_t	abort_fn,
		apr_allocator_t *	allocator,
		const char *	file_line
	)

Debug version of apr_pool_create_unmanaged_ex.

Parameters

newpool

See also

apr_pool_create_unmanaged.

Parameters

abort_fn

See also

apr_pool_create_unmanaged.

Parameters

allocator

See also

apr_pool_create_unmanaged.

Parameters

file_line

Where the function is called from. This is usually APR_POOL__FILE_LINE__.

Remarks

Only available when APR_POOL_DEBUG is defined. Call this directly if you have your apr_pool_create_unmanaged_ex calls in a wrapper function and wish to override the file_line argument to reflect the caller of your wrapper function. If you do not have apr_pool_create_unmanaged_ex in a wrapper, trust the macro and don't call apr_pool_create_unmanaged_ex_debug directly.

void apr_pool_destroy

(

apr_pool_t *

p

)

Destroy the pool. This takes similar action as apr_pool_clear() and then frees all the memory.

Parameters

p	The pool to destroy

Remarks

This will actually free the memory

void apr_pool_destroy_debug	(	apr_pool_t *	p,
		const char *	file_line
	)

Debug version of apr_pool_destroy.

Parameters

p	See: apr_pool_destroy.
file_line	Where the function is called from. This is usually APR_POOL__FILE_LINE__.

Remarks

Only available when APR_POOL_DEBUG is defined. Call this directly if you have your apr_pool_destroy calls in a wrapper function and wish to override the file_line argument to reflect the caller of your wrapper function. If you do not have apr_pool_destroy in a wrapper, trust the macro and don't call apr_pool_destroy_debug directly.

apr_status_t apr_pool_initialize

(

void

)

Setup all of the internal structures required to use pools

Remarks

Programs do NOT need to call this directly. APR will call this automatically from apr_initialize.

int apr_pool_is_ancestor	(	apr_pool_t *	a,
		apr_pool_t *	b
	)

Determine if pool a is an ancestor of pool b.

Parameters

a	The pool to search
b	The pool to search for

Returns

True if a is an ancestor of b, NULL is considered an ancestor of all pools.

Remarks

if compiled with APR_POOL_DEBUG, this function will also return true if A is a pool which has been guaranteed by the caller (using apr_pool_join) to have a lifetime at least as long as some ancestor of pool B.

apr_pool_t* apr_pool_parent_get

(

apr_pool_t *

pool

)

Get the parent pool of the specified pool.

Parameters

pool	The pool for retrieving the parent pool.

Returns

The parent of the given pool.

void apr_pool_tag	(	apr_pool_t *	pool,
		const char *	tag
	)

Tag a pool (give it a name)

Parameters

pool	The pool to tag
tag	The tag

void apr_pool_terminate

(

void

)

Tear down all of the internal structures required to use pools

Remarks

Programs do NOT need to call this directly. APR will call this automatically from apr_terminate.

apr_status_t apr_pool_userdata_get	(	void **	data,
		const char *	key,
		apr_pool_t *	pool
	)

Return the data associated with the current pool.

Parameters

data	The user data associated with the pool.
key	The key for the data to retrieve
pool	The current pool.

apr_status_t apr_pool_userdata_set	(	const void *	data,
		const char *	key,
		apr_status_t(*)(void *)	cleanup,
		apr_pool_t *	pool
	)

Set the data associated with the current pool

Parameters

data	The user data associated with the pool.
key	The key to use for association
cleanup	The cleanup program to use to cleanup the data (NULL if none)
pool	The current pool

Warning

The data to be attached to the pool should have a life span at least as long as the pool it is being attached to.

Users of APR must take EXTREME care when choosing a key to use for their data. It is possible to accidentally overwrite data by choosing a key that another part of the program is using. Therefore it is advised that steps are taken to ensure that unique keys are used for all of the userdata objects in a particular pool (the same key in two different pools or a pool and one of its subpools is okay) at all times. Careful namespace prefixing of key names is a typical way to help ensure this uniqueness.

apr_status_t apr_pool_userdata_setn	(	const void *	data,
		const char *	key,
		apr_status_t(*)(void *)	cleanup,
		apr_pool_t *	pool
	)

Set the data associated with the current pool

Parameters

data	The user data associated with the pool.
key	The key to use for association
cleanup	The cleanup program to use to cleanup the data (NULL if none)
pool	The current pool

Note

same as apr_pool_userdata_set(), except that this version doesn't make a copy of the key (this function is useful, for example, when the key is a string literal)

Warning

This should NOT be used if the key could change addresses by any means between the apr_pool_userdata_setn() call and a subsequent apr_pool_userdata_get() on that key, such as if a static string is used as a userdata key in a DSO and the DSO could be unloaded and reloaded between the _setn() and the _get(). You MUST use apr_pool_userdata_set() in such cases.

More generally, the key and the data to be attached to the pool should have a life span at least as long as the pool itself.