talloc_guide.txt

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


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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.

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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.


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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.

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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.


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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.


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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.


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

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

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


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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


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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)


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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();

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void talloc_disable_null_tracking(void);

This disables tracking of the NULL memory context.

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(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));


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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


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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);


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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)

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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)


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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()


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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 passed
string. This is equivalent to:
   talloc_set_name_const(ptr, ptr)


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

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


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

The talloc_array() macro is equivalent to:

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

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


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

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

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

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

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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.


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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.


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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.


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(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)


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talloc_set_type(const void *ptr, type);

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

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

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talloc_get_size(const void *ctx);

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

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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.

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(type *)talloc_find_parent_bytype(ctx, type);

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