Using talloc in Samba4

======================

.. contents::

Andrew Tridgell

August 2009

The most current version of this document is available at

   http://samba.org/ftp/unpacked/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 use the same context then they need to synchronize in

order to be safe. In particular:

- when using talloc_enable_leak_report(), giving directly NULL as a  

parent context implicitly refers to a hidden "null context" global  

variable, so this should not be used in a multi-threaded environment  

without proper synchronization. In threaded code turn off null tracking using

talloc_disable_null_tracking(). ;

- the context returned by talloc_autofree_context() is also global so  

shouldn't be used by several threads simultaneously without  

synchronization.

talloc and shared objects

-------------------------

talloc can be used in shared objects. Special care needs to be taken

to never use talloc_autofree_context() in code that might be loaded

with dlopen() and unloaded with dlclose(), as talloc_autofree_context()

internally uses atexit(3). Some platforms like modern Linux handles

this fine, but for example FreeBSD does not deal well with dlopen()

and atexit() used simultaneously: dlclose() does not clean up the list

of atexit-handlers, so when the program exits the code that was

registered from within talloc_autofree_context() is gone, the program

crashes at exit.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

(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. A 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. Likewise, if "ptr" is NULL, then the function will make

no modifications and returns -1.

From version 2.0 and onwards, as a special case, talloc_free() is

refused on pointers that have more than one parent associated, as talloc

would have no way of knowing which parent should be removed. This is

different from older versions in the sense that always the reference to

the most recently established parent has been destroyed. Hence to free a

pointer that has more than one parent please use talloc_unlink().

To help you find problems in your code caused by this behaviour, if

you do try and free a pointer with more than one parent then the

talloc logging function will be called to give output like this:

  ERROR: talloc_free with references at some_dir/source/foo.c:123

  	reference at some_dir/source/other.c:325

  	reference at some_dir/source/third.c:121

Please see the documentation for talloc_set_log_fn() and

talloc_set_log_stderr() for more information on talloc logging

functions.

talloc_free() operates recursively on its children.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

void 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.

A NULL argument is handled as no-op.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

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 if it has at maximum one

    parent. This behaviour has been changed since the release of version

    2.0. Further information in the description of "talloc_free".

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

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

int talloc_unlink(const void *context, 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.

You can just use talloc_free() instead of talloc_unlink() if there

is at maximum one parent. This behaviour has been changed since the

release of version 2.0. Further information in the description of

"talloc_free".

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

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.

Note that if you try and call talloc_steal() on a pointer that has

more than one parent then the result is ambiguous. Talloc will choose

to remove the parent that is currently indicated by talloc_parent()

and replace it with the chosen parent. You will also get a message

like this via the talloc logging functions:

  WARNING: talloc_steal with references at some_dir/source/foo.c:123

  	reference at some_dir/source/other.c:325

  	reference at some_dir/source/third.c:121

To unambiguously change the parent of a pointer please see the

function talloc_reparent(). See the talloc_set_log_fn() documentation

for more information on talloc logging.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

void *talloc_reparent(const void *old_parent, const void *new_parent, const void *ptr);

The talloc_reparent() 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_reparent() function returns the pointer that you pass it. It

does not have any failure modes.

The difference between talloc_reparent() and talloc_steal() is that

talloc_reparent() can specify which parent you wish to change. This is

useful when a pointer has multiple parents via references.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

void *talloc_parent(const void *ptr);

The talloc_parent() function returns the current talloc parent. This

is usually the pointer under which this memory was originally created,

but it may have changed due to a talloc_steal() or talloc_reparent()

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

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 entire 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 variant 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 variant 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, unsigned int 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, unsigned int 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, unsigned int 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 of 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 allocated 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.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

void talloc_set_log_fn(void (*log_fn)(const char *message));

This function sets a logging function that talloc will use for

warnings and errors. By default talloc will not print any warnings or

errors.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

void talloc_set_log_stderr(void)

This sets the talloc log function to write log messages to stderr.