+talloc \- hierarchical reference counted memory pool system with destructors
+.SH "SYNOPSIS"
+.sp
+.nf
+#include <talloc\&.h>
+.fi
+.SH "DESCRIPTION"
+.PP
+If you are used to talloc from Samba3 then please read this carefully, as talloc has changed a lot\&.
+.PP
+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\&.
+.PP
+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:
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
+ struct foo *X = talloc(mem_ctx, struct foo);
+ X\->name = talloc_strdup(X, "foo");
+
+.fi
+.if n \{\
+.RE
+.\}
+.PP
+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\&.
+.PP
+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()\&.
+.PP
+If you find this confusing, then I suggest you run the
+testsuite
+program 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\&.
+.SH "TALLOC API"
+.PP
+The following is a complete guide to the talloc API\&. Read it all at least twice\&.
+.SS "(type *)talloc(const void *ctx, type);"
+.PP
+The talloc() macro is the core of the talloc library\&. It takes a memory
+\fIctx\fR
+and a
+\fItype\fR, and returns a pointer to a new area of memory of the given
+\fItype\fR\&.
+.PP
+The returned pointer is itself a talloc context, so you can use it as the
+\fIctx\fR
+argument to more calls to talloc() if you wish\&.
+.PP
+The returned pointer is a "child" of the supplied context\&. This means that if you talloc_free() the
+\fIctx\fR
+then the new child disappears as well\&. Alternatively you can free just the child\&.
+.PP
+The
+\fIctx\fR
+argument to talloc() can be NULL, in which case a new top level context is created\&.
+The function talloc_size() should be used when you don\*(Aqt 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\&.
+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\&.
+.SS "int talloc_free(void *ptr);"
+.PP
+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()\&.
+.PP
+The return value of talloc_free() indicates success or failure, with 0 returned for success and \-1 for failure\&. The only possible failure condition is if
+\fIptr\fR
+had a destructor attached to it and the destructor returned \-1\&. See
+\(lqtalloc_set_destructor()\(rq
+for details on destructors\&.
+.PP
+If this pointer has an additional parent when talloc_free() is called then the memory is not actually released, but instead the most recently established parent is destroyed\&. See
+\(lqtalloc_reference()\(rq
+for details on establishing additional parents\&.
+.PP
+For more control on which parent is removed, see
+\(lqtalloc_unlink()\(rq\&.
+.PP
+talloc_free() operates recursively on its children\&.
+.PP
+From the 2\&.0 version of talloc, as a special case, talloc_free() is refused on pointers that have more than one parent, as talloc would have no way of knowing which parent should be removed\&. To free a pointer that has more than one parent please use talloc_unlink()\&.
+.PP
+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:
+.PP
+.if n \{\
+.RS 4
+.\}
+.nf
+ 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
+
+.fi
+.if n \{\
+.RE
+.\}
+.PP
+Please see the documentation for talloc_set_log_fn() and talloc_set_log_stderr() for more information on talloc logging functions\&.
+The return value of talloc_reference() is always the original pointer
+\fIptr\fR, 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)\&.
+.PP
+If
+\fIptr\fR
+is NULL, then the function is a no\-op, and simply returns NULL\&.
+.PP
+After creating a reference you can free it in one of the following ways:
+.PP
+.RS 4
+.ie n \{\
+\h'-04'\(bu\h'+03'\c
+.\}
+.el \{\
+.sp -1
+.IP \(bu 2.3
+.\}
+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\&.
+.RE
+.sp
+.RS 4
+.ie n \{\
+\h'-04'\(bu\h'+03'\c
+.\}
+.el \{\
+.sp -1
+.IP \(bu 2.3
+.\}
+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 informations in the description of "talloc_free"\&.
+The talloc_unlink() function removes a specific parent from
+\fIptr\fR\&. The
+\fIctx\fR
+passed must either be a context used in talloc_reference() with this pointer, or must be a direct parent of ptr\&.
+.PP
+Note that if the parent has already been removed using talloc_free() then this function will fail and will return \-1\&. Likewise, if
+\fIptr\fR
+is NULL, then the function will make no modifications and return \-1\&.
+.PP
+Usually you can just use talloc_free() instead of talloc_unlink(), but sometimes it is useful to have the additional control on which parent is removed\&.
+.SS "void talloc_set_destructor(const void *ptr, int (*destructor)(void *));"
+.PP
+The function talloc_set_destructor() sets the
+\fIdestructor\fR
+for the pointer
+\fIptr\fR\&. A
+\fIdestructor\fR
+is a function that is called when the memory used by a pointer is about to be released\&. The destructor receives
+\fIptr\fR
+as an argument, and should return 0 for success and \-1 for failure\&.
+.PP
+The
+\fIdestructor\fR
+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\&.
+.PP
+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\&.
+.PP
+To remove a destructor call talloc_set_destructor() with NULL for the destructor\&.
+.PP
+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\&.
+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\&.
+.PP
+The main use for names on pointer is for "talloc reports"\&. See
+\(lqtalloc_report_depth_cb()\(rq,
+\(lqtalloc_report_depth_file()\(rq,
+\(lqtalloc_report()\(rq
+\(lqtalloc_report()\(rq
+and
+\(lqtalloc_report_full()\(rq
+for details\&. Also see
+\(lqtalloc_enable_leak_report()\(rq
+and
+\(lqtalloc_enable_leak_report_full()\(rq\&.
+.PP
+The talloc_set_name() function allocates memory as a child of the pointer\&. It is logically equivalent to:
+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()\&.
+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()\&.
+.PP
+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
+This function creates a zero length named talloc context as a top level context\&. It is equivalent to:
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
+talloc_named(NULL, 0, fmt, \&.\&.\&.);
+.fi
+.if n \{\
+.RE
+.\}
+.SS "void *talloc_new(void *\fIctx\fR);"
+.PP
+This is a utility macro that creates a new memory context hanging off an existing 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\&.
+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
+the talloc_realloc_size() function is useful when the type is not known so the type\-safe talloc_realloc() cannot be used\&.
+.SS "TYPE *talloc_steal(const void *\fInew_ctx\fR, const TYPE *\fIptr\fR);"
+.PP
+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\&.
+.PP
+The talloc_steal() function returns the pointer that you pass it\&. It does not have any failure modes\&.
+.PP
+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\&.
+.PP
+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:
+.PP
+.if n \{\
+.RS 4
+.\}
+.nf
+ 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
+
+.fi
+.if n \{\
+.RE
+.\}
+.PP
+To unambiguously change the parent of a pointer please see the function
+\(lqtalloc_reparent()\(rq\&. See the talloc_set_log_fn() documentation for more information on talloc logging\&.
+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\&.
+.PP
+The talloc_reparent() function returns the pointer that you pass it\&. It does not have any failure modes\&.
+.PP
+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\&.
+.SS "TYPE *talloc_move(const void *\fInew_ctx\fR, TYPE **\fIptr\fR);"
+.PP
+The talloc_move() function is a wrapper around talloc_steal() which zeros the source pointer after the move\&. This avoids a potential source of bugs where a programmer leaves a pointer in two structures, and uses the pointer from the old structure after it has been moved to a new one\&.
+The talloc_total_size() function returns the total size in bytes used by this pointer and all child pointers\&. Mostly useful for debugging\&.
+.PP
+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\&.
+The talloc_total_blocks() function returns the total memory block count used by this pointer and all child pointers\&. Mostly useful for debugging\&.
+.PP
+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\&.
+The talloc_report() function prints a summary report of all memory used by
+\fIptr\fR\&. One line of report is printed for each immediate child of ptr, showing the total memory and number of blocks used by that child\&.
+.PP
+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\&.
+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\&.
+.PP
+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\&.
+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
+\fIis_ref = 1\fR
+and the pointer that is referenced\&.
+.PP
+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\&.
+.PP
+The recursion is stopped when depth >= max_depth\&. max_depth = \-1 means only stop at leaf nodes\&.
+This provides a more flexible reports than talloc_report()\&. It will let you specify the depth and max_depth\&.
+.SS "void talloc_enable_leak_report(void);"
+.PP
+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\&.
+.PP
+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\*(Aqt call this function first then passing NULL to talloc_report() or talloc_report_full() won\*(Aqt give you the full tree printout\&.
+.PP
+Here is a typical talloc report:
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
+talloc report on \*(Aqnull_context\*(Aq (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
+
+.fi
+.if n \{\
+.RE
+.\}
+.SS "void talloc_enable_leak_report_full(void);"
+.PP
+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\&.
+.PP
+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\*(Aqt call this function first then passing NULL to talloc_report() or talloc_report_full() won\*(Aqt give you the full tree printout\&.
+.PP
+Here is a typical full report:
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
+full talloc report on \*(Aqroot\*(Aq (total 18 bytes in 8 blocks)
+The talloc_asprintf_append() function appends the given formatted string to the given string\&.
+.PP
+This function sets the name of the new pointer to the new string\&. This is equivalent to:
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
+talloc_set_name_const(ptr, ptr)
+.fi
+.if n \{\
+.RE
+.\}
+.SS "(type *)talloc_array(const void *ctx, type, unsigned int count);"
+.PP
+The talloc_array() macro is equivalent to:
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
+(type *)talloc_size(ctx, sizeof(type) * count);
+.fi
+.if n \{\
+.RE
+.\}
+.PP
+except that it provides integer overflow protection for the multiply, returning NULL if the multiply overflows\&.
+.SS "void *talloc_array_size(const void *ctx, size_t size, unsigned int count);"
+.PP
+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\&.
+.SS "(typeof(ptr)) talloc_array_ptrtype(const void *ctx, ptr, unsigned int count);"
+.PP
+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\&.
+This is a non\-macro version of talloc_realloc(), which is useful as libraries sometimes want a realloc function pointer\&. A realloc(3) implementation encapsulates the functionality of malloc(3), free(3) and realloc(3) in one call, which is why it is useful to be able to pass around a single function pointer\&.
+.SS "void *talloc_autofree_context(void);"
+.PP
+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\&.
+This function sets a logging function that talloc will use for warnings and errors\&. By default talloc will not print any warnings or errors\&.
+.SS "talloc_set_log_stderr(void);"
+.PP
+This sets the talloc log function to write log messages to stderr
+.SH "PERFORMANCE"
+.PP
+All the additional features of talloc(3) over malloc(3) 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 10% 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\&.
+The original Samba software and related utilities were created by Andrew Tridgell\&. Samba is now developed by the Samba Team as an Open Source project similar to the way the Linux kernel is developed\&.
+.SH "COPYRIGHT/LICENSE"
+.PP
+Copyright (C) Andrew Tridgell 2004
+.PP
+This program is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version\&.
+.PP
+This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE\&. See the GNU General Public License for more details\&.
+.PP
+You should have received a copy of the GNU General Public License along with this program; if not, see http://www\&.gnu\&.org/licenses/\&.