Adding upstream version 2.4.2.upstream/2.4.2upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

13 files changed, 1204 insertions, 0 deletions

diff --git a/doc/context.png b/doc/context.png
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index 0000000..48a6ca0
--- /dev/null
+++ b/doc/context.png
diff --git a/doc/context_tree.png b/doc/context_tree.png
new file mode 100644
index 0000000..9723459
--- /dev/null
+++ b/doc/context_tree.png
diff --git a/doc/mainpage.dox b/doc/mainpage.dox
new file mode 100644
index 0000000..ece6ccb
--- /dev/null
+++ b/doc/mainpage.dox
@@ -0,0 +1,111 @@
+/**
+ * @mainpage
+ *
+ * talloc is a hierarchical, reference counted memory pool system with
+ * destructors. It is the core memory allocator used in Samba.
+ *
+ * @section talloc_download Download
+ *
+ * You can download the latest releases of talloc from the
+ * <a href="http://samba.org/ftp/talloc" target="_blank">talloc directory</a>
+ * on the samba public source archive.
+ *
+ * @section main-tutorial Tutorial
+ *
+ * You should start by reading @subpage libtalloc_tutorial, then reading the documentation of
+ * the interesting functions as you go.
+
+ * @section talloc_bugs Discussion and bug reports
+ *
+ * talloc does not currently have its own mailing list or bug tracking system.
+ * For now, please use the
+ * <a href="https://lists.samba.org/mailman/listinfo/samba-technical" target="_blank">samba-technical</a>
+ * mailing list, and the
+ * <a href="http://bugzilla.samba.org/" target="_blank">Samba bugzilla</a>
+ * bug tracking system.
+ *
+ * @section talloc_devel Development
+ * You can download the latest code either via git or rsync.
+ *
+ * To fetch via git see the following guide:
+ *
+ * <a href="http://wiki.samba.org/index.php/Using_Git_for_Samba_Development" target="_blank">Using Git for Samba Development</a>
+ *
+ * Once you have cloned the tree switch to the master branch and cd into the
+ * lib/tevent directory.
+ *
+ * To fetch via rsync use this command:
+ *
+ * rsync -Pavz samba.org::ftp/unpacked/standalone_projects/lib/talloc .
+ *
+ * @section talloc_preample Preamble
+ *
+ * talloc is a hierarchical, reference counted memory pool system with
+ * destructors.
+ *
+ * Perhaps the biggest difference from other memory pool systems 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:
+ *
+ * @code
+ *      struct foo *X = talloc(mem_ctx, struct foo);
+ *      X->name = talloc_strdup(X, "foo");
+ * @endcode
+ *
+ * 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 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.
+ *
+ * @section talloc_performance 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.
+ *
+ * @section talloc_named Named blocks
+ *
+ * Every talloc chunk has a name that can be used as a dynamic type-checking
+ * system. If for some reason like a callback function you had to cast a
+ * "struct foo *" to a "void *" variable, later you can safely reassign the
+ * "void *" pointer to a "struct foo *" by using the talloc_get_type() or
+ * talloc_get_type_abort() macros.
+ *
+ * @code
+ *      struct foo *X = talloc_get_type_abort(ptr, struct foo);
+ * @endcode
+ *
+ * This will abort if "ptr" does not contain a pointer that has been created
+ * with talloc(mem_ctx, struct foo).
+ *
+ * @section talloc_threading 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 uses 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.
+ *
+ */
diff --git a/doc/stealing.png b/doc/stealing.png
new file mode 100644
index 0000000..8833e06
--- /dev/null
+++ b/doc/stealing.png
diff --git a/doc/tutorial_bestpractices.dox b/doc/tutorial_bestpractices.dox
new file mode 100644
index 0000000..3634446
--- /dev/null
+++ b/doc/tutorial_bestpractices.dox
@@ -0,0 +1,192 @@
+/**
+@page libtalloc_bestpractices Chapter 7: Best practises
+
+The following sections contain several best practices and good manners that were
+found by the <a href="http://www.samba.org">Samba</a> and
+<a href="https://fedorahosted.org/sssd">SSSD</a> developers over the years.
+These will help you to write code which is better, easier to debug and with as
+few (hopefully none) memory leaks as possible.
+
+@section bp-hierarchy Keep the context hierarchy steady
+
+The talloc is a hierarchy memory allocator. The hierarchy nature is what makes
+the programming more error proof. It makes the memory easier to manage and to
+free.  Therefore, the first thing we should have on our mind is: always project
+your data structures into the talloc context hierarchy.
+
+That means if we have a structure, we should always use it as a parent context
+for its elements. This way we will not encounter any troubles when freeing the
+structure or when changing its parent. The same rule applies for arrays.
+
+For example, the structure <code>user</code> from section @ref context-hierarchy
+should be created with the context hierarchy illustrated on the next image.
+
+@image html context_tree.png
+
+@section bp-tmpctx Every function should use its own context
+
+It is a good practice to create a temporary talloc context at the function
+beginning and free the context just before the return statement. All the data
+must be allocated on this context or on its children. This ensures that no
+memory leaks are created as long as we do not forget to free the temporary
+context.
+
+This pattern applies to both situations - when a function does not return any
+dynamically allocated value and when it does. However, it needs a little
+extension for the latter case.
+
+@subsection bp-tmpctx-1 Functions that do not return any dynamically allocated
+value
+
+If the function does not return any value created on the heap, we will just obey
+the aforementioned pattern.
+
+@code
+int bar()
+{
+  int ret;
+  TALLOC_CTX *tmp_ctx = talloc_new(NULL);
+  if (tmp_ctx == NULL) {
+    ret = ENOMEM;
+    goto done;
+  }
+  /* allocate data on tmp_ctx or on its descendants */
+  ret = EOK;
+done:
+  talloc_free(tmp_ctx);
+  return ret;
+}
+@endcode
+
+@subsection bp-tmpctx-2 Functions returning dynamically allocated values
+
+If our function returns any dynamically allocated data, its first parameter
+should always be the destination talloc context. This context serves as a parent
+for the output values. But again, we will create the output values as the
+descendants of the temporary context. If everything goes well, we will change
+the parent of the output values from the temporary to the destination talloc
+context.
+
+This pattern ensures that if an error occurs (e.g. I/O error or insufficient
+amount of the memory), all allocated data is freed and no garbage appears on
+the destination context.
+
+@code
+int struct_foo_init(TALLOC_CTX *mem_ctx, struct foo **_foo)
+{
+  int ret;
+  struct foo *foo = NULL;
+  TALLOC_CTX *tmp_ctx = talloc_new(NULL);
+  if (tmp_ctx == NULL) {
+    ret = ENOMEM;
+    goto done;
+  }
+  foo = talloc_zero(tmp_ctx, struct foo);
+  /* ... */
+  *_foo = talloc_steal(mem_ctx, foo);
+  ret = EOK;
+done:
+  talloc_free(tmp_ctx);
+  return ret;
+}
+@endcode
+
+@section bp-null Allocate temporary contexts on NULL
+
+As it can be seen on the previous listing, instead of allocating the temporary
+context directly on <code>mem_ctx</code>, we created a new top level context
+using <code>NULL</code> as the parameter for <code>talloc_new()</code> function.
+Take a look at the following example:
+
+@code
+char *create_user_filter(TALLOC_CTX *mem_ctx,
+                         uid_t uid, const char *username)
+{
+  char *filter = NULL;
+  char *sanitized_username = NULL;
+  /* tmp_ctx is a child of mem_ctx */
+  TALLOC_CTX *tmp_ctx = talloc_new(mem_ctx);
+  if (tmp_ctx == NULL) {
+    return NULL;
+  }
+
+  sanitized_username = sanitize_string(tmp_ctx, username);
+  if (sanitized_username == NULL) {
+    talloc_free(tmp_ctx);
+    return NULL;
+  }
+
+  filter = talloc_aprintf(tmp_ctx,"(|(uid=%llu)(uname=%s))",
+                          uid, sanitized_username);
+  if (filter == NULL) {
+    return NULL; /* tmp_ctx is not freed */ (*@\label{lst:tmp-ctx-3:leak}@*)
+  }
+
+  /* filter becomes a child of mem_ctx */
+  filter = talloc_steal(mem_ctx, filter);
+  talloc_free(tmp_ctx);
+  return filter;
+}
+@endcode
+
+We forgot to free <code>tmp_ctx</code> before the <code>return</code> statement
+in the <code>filter == NULL</code> condition. However, it is created as a child
+of <code>mem_ctx</code> context and as such it will be freed as soon as the
+<code>mem_ctx</code> is freed. Therefore, no detectable memory leak is created.
+
+On the other hand, we do not have any way to access the allocated data
+and for all we know <code>mem_ctx</code> may exist for the lifetime of our
+application. For these reasons this should be considered as a memory leak. How
+can we detect if it is unreferenced but still attached to its parent context?
+The only way is to notice the mistake in the source code.
+
+But if we create the temporary context as a top level context, it will not be
+freed and memory diagnostic tools
+(e.g. <a href="http://valgrind.org">valgrind</a>) are able to do their job.
+
+@section bp-pool Temporary contexts and the talloc pool
+
+If we want to take the advantage of the talloc pool but also keep to the
+pattern introduced in the previous section, we are unable to do it directly. The
+best thing to do is to create a conditional build where we can decide how do we
+want to create the temporary context. For example, we can create the following
+macros:
+
+@code
+#ifdef USE_POOL_CONTEXT
+  #define CREATE_POOL_CTX(ctx, size) talloc_pool(ctx, size)
+  #define CREATE_TMP_CTX(ctx)        talloc_new(ctx)
+#else
+  #define CREATE_POOL_CTX(ctx, size) talloc_new(ctx)
+  #define CREATE_TMP_CTX(ctx)        talloc_new(NULL)
+#endif
+@endcode
+
+Now if our application is under development, we will build it with macro
+<code>USE_POOL_CONTEXT</code> undefined. This way, we  can use memory diagnostic
+utilities to detect memory leaks.
+
+The release version will be compiled with the macro defined. This will  enable
+pool contexts and therefore reduce the <code>malloc()</code> calls, which will
+end up in a little bit faster processing.
+
+@code
+int struct_foo_init(TALLOC_CTX *mem_ctx, struct foo **_foo)
+{
+  int ret;
+  struct foo *foo = NULL;
+  TALLOC_CTX *tmp_ctx = CREATE_TMP_CTX(mem_ctx);
+  /* ... */
+}
+
+errno_t handle_request(TALLOC_CTX mem_ctx)
+{
+  int ret;
+  struct foo *foo = NULL;
+  TALLOC_CTX *pool_ctx = CREATE_POOL_CTX(NULL, 1024);
+  ret = struct_foo_init(mem_ctx, &foo);
+  /* ... */
+}
+@endcode
+
+*/
diff --git a/doc/tutorial_context.dox b/doc/tutorial_context.dox
new file mode 100644
index 0000000..b8bfe26
--- /dev/null
+++ b/doc/tutorial_context.dox
@@ -0,0 +1,198 @@
+/**
+@page libtalloc_context Chapter 1: Talloc context
+@section context Talloc context
+
+The talloc context is the most important part of this library and is
+responsible for every single feature of this memory allocator. It is a logical
+unit which represents a memory space managed by talloc.
+
+From the programmer's point of view, the talloc context is completely
+equivalent to a pointer that would be returned by the memory routines from the
+C standard library. This means that every context that is returned from the
+talloc library can be used directly in functions that do not use talloc
+internally. For example we can do the following:
+
+@code
+char *str1 = strdup("I am NOT a talloc context");
+char *str2 = talloc_strdup(NULL, "I AM a talloc context");
+
+printf("%d\n", strcmp(str1, str2) == 0);
+
+free(str1);
+talloc_free(str2); /* we can not use free() on str2 */
+@endcode
+
+This is possible because the context is internally handled as a special
+fixed-length structure called talloc chunk. Each chunk stores context metadata
+followed by the memory space requested by the programmer. When a talloc
+function returns a context (pointer), it will in fact return a pointer to the user
+space portion of the talloc chunk. If we to manipulate this context using
+talloc functions, the talloc library transforms the user-space pointer back to
+the starting address of the chunk. This is also the reason why we were unable
+to use <code>free(str2)</code> in the previous example - because
+<code>str2</code> does not point at the beginning of the allocated block of
+memory. This is illustrated on the next image:
+
+@image html context.png
+
+The type TALLOC_CTX is defined in talloc.h to identify a talloc context in
+function parameters. However, this type is just an alias for <code>void</code>
+and exists only for semantical reasons - thus we can differentiate between
+<code>void *</code> (arbitrary data) and <code>TALLOC_CTX *</code> (talloc
+context).
+
+@subsection metadata Context meta data
+
+Every talloc context carries several pieces of internal information along with
+the allocated memory:
+
+  - name - which is used in reports of context hierarchy and to simulate
+    a dynamic type system,
+  - size of the requested memory in bytes - this can be used to determine
+    the number of elements in arrays,
+  - attached destructor - which is executed just before the memory block is
+    about to be freed,
+  - references to the context
+  - children and parent contexts - create the hierarchical view on the
+    memory.
+
+@section context-hierarchy Hierarchy of talloc context
+
+Every talloc context contains information about its parent and children. Talloc
+uses this information to create a hierarchical model of memory or to be more
+precise, it creates an n-ary tree where each node represents a single talloc
+context. The root node of the tree is referred to as a top level context - a
+context without any parent.
+
+This approach has several advantages:
+
+  - as a consequence of freeing a talloc context, all of its children
+    will be properly deallocated as well,
+  - the parent of a context can be changed at any time, which
+    results in moving the whole subtree under another node,
+  - it creates a more natural way of managing data structures.
+
+@subsection Example
+
+We have a structure that stores basic information about a user - his/her name,
+identification number and groups he/she is a member of:
+
+@code
+struct user {
+  uid_t uid;
+  char *username;
+  size_t num_groups;
+  char **groups;
+};
+@endcode
+
+We will allocate this structure using talloc. The result will be the following
+context tree:
+
+@image html context_tree.png
+
+@code
+/* create new top level context */
+struct user *user = talloc(NULL, struct user);
+
+user->uid = 1000;
+user->num_groups = N;
+
+/* make user the parent of following contexts */
+user->username = talloc_strdup(user, "Test user");
+user->groups = talloc_array(user, char*, user->num_groups);
+
+for (i = 0; i < user->num_groups; i++) {
+  /* make user->groups the parent of following context */
+  user->groups[i] = talloc_asprintf(user->groups,
+                                    "Test group %d", i);
+}
+@endcode
+
+This way, we have gained a lot of additional capabilities, one of which is
+very simple deallocation of the structure and all of its elements.
+
+With the C standard library we need first to iterate over the array of groups
+and free every element separately. Then we must deallocate the array that stores
+them. Next we deallocate the username and as the last step free the structure
+itself. But with talloc, the only operation we need to execute is freeing the
+structure context. Its descendants will be freed automatically.
+
+@code
+talloc_free(user);
+@endcode
+
+@section keep-hierarchy Always keep the hieararchy steady!
+
+The talloc is a hierarchy memory allocator. The hierarchy nature is what makes
+the programming more error proof. It makes the memory easier to manage and to
+free.  Therefore, the first thing we should have on our mind is: <strong>always
+project our data structures into the talloc context hierarchy</strong>.
+
+That means if we have a structure, we should always use it as a parent context
+for its elements. This way we will not encounter any troubles when freeing this
+structure or when changing its parent. The same rule applies for arrays.
+
+@section creating-context Creating a talloc context
+
+Here are the most important functions that create a new talloc context.
+
+@subsection type-safe Type-safe functions
+
+It allocates the size that is necessary for the given type and returns a new,
+properly-casted pointer. This is the preferred way to create a new context as
+we can rely on the compiler to detect type mismatches.
+
+The name of the context is automatically set to the name of the data type which
+is used to simulate a dynamic type system.
+
+@code
+struct user *user = talloc(ctx, struct user);
+
+/* initialize to default values */
+user->uid = 0;
+user->name = NULL;
+user->num_groups = 0;
+user->groups = NULL;
+
+/* or we can achieve the same result with */
+struct user *user_zero = talloc_zero(ctx, struct user);
+@endcode
+
+@subsection zero-length Zero-length contexts
+
+The zero-length context is basically a context without any special semantical
+meaning. We can use it the same way as any other context. The only difference
+is that it consists only of the meta data about the context. Therefore, it is
+strictly of type <code>TALLOC_CTX*</code>. It is often used in cases where we
+want to aggregate several data structures under one parent (zero-length)
+context, such as a temporary context to contain memory needed within a single
+function that is not interesting to the caller. Allocating on a zero-length
+temporary context will make clean-up of the function simpler.
+
+@code
+TALLOC_CTX *tmp_ctx = NULL;
+struct foo *foo = NULL;
+struct bar *bar = NULL;
+
+/* new zero-length top level context */
+tmp_ctx = talloc_new(NULL);
+if (tmp_ctx == NULL) {
+  return ENOMEM;
+}
+
+foo = talloc(tmp_ctx, struct foo);
+bar = talloc(tmp_ctx, struct bar);
+
+/* free everything at once */
+talloc_free(tmp_ctx);
+@endcode
+
+@subsection context-see-also See also
+
+- talloc_size()
+- talloc_named()
+- @ref talloc_array
+- @ref talloc_string
+
+*/
diff --git a/doc/tutorial_debugging.dox b/doc/tutorial_debugging.dox
new file mode 100644
index 0000000..aadbb0d
--- /dev/null
+++ b/doc/tutorial_debugging.dox
@@ -0,0 +1,116 @@
+/**
+@page libtalloc_debugging Chapter 6: Debugging
+
+Although talloc makes memory management significantly easier than the C standard
+library, developers are still only humans and can make mistakes. Therefore, it
+can be handy to know some tools for the inspection of talloc memory usage.
+
+@section log-abort Talloc log and abort
+
+We have already encountered the abort function in section @ref dts.
+In that case it was used when a type mismatch was detected. However, talloc
+calls this abort function in several more situations:
+
+- when the provided pointer is not a valid talloc context,
+- when the meta data is invalid - probably due to memory corruption,
+- and when an access after free is detected.
+
+The third one is probably the most interesting. It can help us with detecting
+an attempt to double-free a context or any other manipulation with it via
+talloc functions (using it as a parent, stealing it, etc.).
+
+Before the context is freed talloc sets a flag in the meta data. This is then
+used to detect the access after free. It basically works on the assumption that
+the memory stays unchanged (at least for a while) even when it is properly
+deallocated. This will work even if the memory is filled with the value
+specified in <code>TALLOC_FREE_FILL</code> environment variable, because it
+fills only the data part and leaves the meta data intact.
+
+Apart from the abort function, talloc uses a log function to provide additional
+information to the aforementioned violations. To enable logging we shall set the
+log function with one of:
+
+- talloc_set_log_fn()
+- talloc_set_log_stderr()
+
+The following code is a sample output of accessing a context after it has been
+freed:
+
+@code
+talloc_set_log_stderr();
+TALLOC_CTX *ctx = talloc_new(NULL);
+
+talloc_free(ctx);
+talloc_free(ctx);
+
+results in:
+talloc: access after free error - first free may be at ../src/main.c:55
+Bad talloc magic value - access after free
+@endcode
+
+Another example is an invalid context:
+
+@code
+talloc_set_log_stderr();
+TALLOC_CTX *ctx = talloc_new(NULL);
+char *str = strdup("not a talloc context");
+talloc_steal(ctx, str);
+
+results in:
+Bad talloc magic value - unknown value
+@endcode
+
+@section reports Memory usage reports
+
+Talloc can print reports of memory usage of a specified talloc context to a
+file (to <code>stdout</code> or <code>stderr</code>). The report can be
+simple or full. The simple report provides information only about the context
+itself and its direct descendants. The full report goes recursively through the
+entire context tree. See:
+
+- talloc_report()
+- talloc_report_full()
+
+We will use the following code to retrieve the sample report:
+
+@code
+struct foo {
+  char *str;
+};
+
+TALLOC_CTX *ctx = talloc_new(NULL);
+char *str =  talloc_strdup(ctx, "my string");
+struct foo *foo = talloc_zero(ctx, struct foo);
+foo->str = talloc_strdup(foo, "I am Foo");
+char *str2 = talloc_strdup(foo, "Foo is my parent");
+
+/* print full report */
+talloc_report_full(ctx, stdout);
+@endcode
+
+It will print a full report of <code>ctx</code> to the standard output.
+The message should be similar to:
+
+@code
+full talloc report on 'talloc_new: ../src/main.c:82' (total 46 bytes in 5 blocks)
+  struct foo contains 34 bytes in 3 blocks (ref 0) 0x1495130
+    Foo is my parent contains 17 bytes in 1 blocks (ref 0) 0x1495200
+    I am Foo contains 9 bytes in 1 blocks (ref 0) 0x1495190
+  my string contains 10 bytes in 1 blocks (ref 0) 0x14950c0
+@endcode
+
+We can notice in this report that something is wrong with the context containing
+<code>struct foo</code>. We know that the structure has only one string element.
+However, we can see in the report that it has two children. This indicates that
+we have either violated the memory hierarchy or forgotten to free it as
+temporary data. Looking into the code, we can see that <code>"Foo is my parent"
+</code> should be attached to <code>ctx</code>.
+
+See also:
+
+- talloc_enable_null_tracking()
+- talloc_disable_null_tracking()
+- talloc_enable_leak_report()
+- talloc_enable_leak_report_full()
+
+*/
diff --git a/doc/tutorial_destructors.dox b/doc/tutorial_destructors.dox
new file mode 100644
index 0000000..ed06387
--- /dev/null
+++ b/doc/tutorial_destructors.dox
@@ -0,0 +1,82 @@
+/**
+@page libtalloc_destructors Chapter 4: Using destructors
+
+@section destructors Using destructors
+
+Destructors are well known methods in the world of object oriented programming.
+A destructor is a method of an object that is automatically run when the object
+is destroyed. It is usually used to return resources taken by the object back to
+the system (e.g. closing file descriptors, terminating connection to a database,
+deallocating memory).
+
+With talloc we can take the advantage of destructors even in C. We can easily
+attach our own destructor to a talloc context. When the context is freed, the
+destructor will run automatically.
+
+To attach/detach a destructor to a talloc context use: talloc_set_destructor().
+
+@section destructors-example Example
+
+Imagine that we have a dynamically created linked list. Before we deallocate an
+element of the list, we need to make sure that we have successfully removed it
+from the list. Normally, this would be done by two commands in the exact order:
+remove it from the list and then free the element. With talloc, we can do this
+at once by setting a destructor on the element which will remove it from the
+list and talloc_free() will do the rest.
+
+The destructor would be:
+
+@code
+int list_remove(void *ctx)
+{
+    struct list_el *el = NULL;
+    el = talloc_get_type_abort(ctx, struct list_el);
+    /* remove element from the list */
+}
+@endcode
+
+GCC version 3 and newer can check for the types during the compilation. So if
+it is our major compiler, we can use a more advanced destructor:
+
+@code
+int list_remove(struct list_el *el)
+{
+    /* remove element from the list */
+}
+@endcode
+
+Now we will assign the destructor to the list element. We can do this directly
+in the function that inserts it.
+
+@code
+struct list_el* list_insert(TALLOC_CTX *mem_ctx,
+                            struct list_el *where,
+                            void *ptr)
+{
+  struct list_el *el = talloc(mem_ctx, struct list_el);
+  el->data = ptr;
+  /* insert into list */
+
+  talloc_set_destructor(el, list_remove);
+  return el;
+}
+@endcode
+
+Because talloc is a hierarchical memory allocator, we can go a step further and
+free the data with the element as well:
+
+@code
+struct list_el* list_insert_free(TALLOC_CTX *mem_ctx,
+                                 struct list_el *where,
+                                 void *ptr)
+{
+  struct list_el *el = NULL;
+  el = list_insert(mem_ctx, where, ptr);
+
+  talloc_steal(el, ptr);
+
+  return el;
+}
+@endcode
+
+*/
diff --git a/doc/tutorial_dts.dox b/doc/tutorial_dts.dox
new file mode 100644
index 0000000..75b5172
--- /dev/null
+++ b/doc/tutorial_dts.dox
@@ -0,0 +1,109 @@
+/**
+@page libtalloc_dts Chapter 3: Dynamic type system
+
+@section dts Dynamic type system
+
+Generic programming in the C language is very difficult. There is no inheritance
+nor templates known from object oriented languages. There is no dynamic type
+system. Therefore, generic programming in this language is usually done by
+type-casting a variable to <code>void*</code> and transferring it through
+a generic function to a specialized callback as illustrated on the next listing.
+
+@code
+void generic_function(callback_fn cb, void *pvt)
+{
+  /* do some stuff and call the callback */
+  cb(pvt);
+}
+
+void specific_callback(void *pvt)
+{
+  struct specific_struct *data;
+  data = (struct specific_struct*)pvt;
+  /* ... */
+}
+
+void specific_function()
+{
+  struct specific_struct data;
+  generic_function(callback, &data);
+}
+@endcode
+
+Unfortunately, the type information is lost as a result of this type cast. The
+compiler cannot check the type during the compilation nor are we able to do it
+at runtime. Providing an invalid data type to the callback will result in
+unexpected behaviour (not necessarily a crash) of the application. This mistake
+is usually hard to detect because it is not the first thing which comes the
+mind.
+
+As we already know, every talloc context contains a name. This name is available
+at any time and it can be used to determine the type of a context even if we
+lose the type of a variable.
+
+Although the name of the context can be set to any arbitrary string, the best
+way of using it to simulate the dynamic type system is to set it directly to the
+type of the variable.
+
+It is recommended to use one of talloc() and talloc_array() (or its
+variants) to create the context as they set its name to the name of the
+given type automatically.
+
+If we have a context with such as a name, we can use two similar functions that
+do both the type check and the type cast for us:
+
+- talloc_get_type()
+- talloc_get_type_abort()
+
+@section dts-examples Examples
+
+The following example will show how generic programming with talloc is handled -
+if we provide invalid data to the callback, the program will be aborted. This
+is a sufficient reaction for such an error in most applications.
+
+@code
+void foo_callback(void *pvt)
+{
+  struct foo *data = talloc_get_type_abort(pvt, struct foo);
+  /* ... */
+}
+
+int do_foo()
+{
+  struct foo *data = talloc_zero(NULL, struct foo);
+  /* ... */
+  return generic_function(foo_callback, data);
+}
+@endcode
+
+But what if we are creating a service application that should be running for the
+uptime of a server, we may want to abort the application during the development
+process (to make sure the error is not overlooked) and try to recover from the
+error in the customer release. This can be achieved by creating a custom abort
+function with a conditional build.
+
+@code
+void my_abort(const char *reason)
+{
+  fprintf(stderr, "talloc abort: %s\n", reason);
+#ifdef ABORT_ON_TYPE_MISMATCH
+  abort();
+#endif
+}
+@endcode
+
+The usage of talloc_get_type_abort() would be then:
+
+@code
+talloc_set_abort_fn(my_abort);
+
+TALLOC_CTX *ctx = talloc_new(NULL);
+char *str = talloc_get_type_abort(ctx, char);
+if (str == NULL) {
+  /* recovery code */
+}
+/* talloc abort: ../src/main.c:25: Type mismatch:
+   name[talloc_new: ../src/main.c:24] expected[char] */
+@endcode
+
+*/
diff --git a/doc/tutorial_introduction.dox b/doc/tutorial_introduction.dox
new file mode 100644
index 0000000..418c38b
--- /dev/null
+++ b/doc/tutorial_introduction.dox
@@ -0,0 +1,45 @@
+/**
+@page libtalloc_tutorial The Tutorial
+@section introduction Introduction
+
+Talloc is a hierarchical, reference counted memory pool system with destructors.
+It is built atop the C standard library and it defines a set of utility
+functions that altogether simplifies allocation and deallocation of data,
+especially for complex structures that contain many dynamically allocated
+elements such as strings and arrays.
+
+The main goals of this library are: removing the needs for creating a cleanup
+function for every complex structure, providing a logical organization of
+allocated memory blocks and reducing the likelihood of creating memory leaks in
+long-running applications. All of this is achieved by allocating memory in a
+hierarchical structure of talloc contexts such that deallocating one context
+recursively frees all of its descendants as well.
+
+@section main-features Main features
+- An open source project
+- A hierarchical memory model
+- Natural projection of data structures into the memory space
+- Simplifies memory management of large data structures
+- Automatic execution of a destructor before the memory is freed
+- Simulates a dynamic type system
+- Implements a transparent memory pool
+
+@section toc Table of contents:
+
+@subpage libtalloc_context
+
+@subpage libtalloc_stealing
+
+@subpage libtalloc_dts
+
+@subpage libtalloc_destructors
+
+@subpage libtalloc_pools
+
+@subpage libtalloc_debugging
+
+@subpage libtalloc_bestpractices
+
+@subpage libtalloc_threads
+
+*/
diff --git a/doc/tutorial_pools.dox b/doc/tutorial_pools.dox
new file mode 100644
index 0000000..a0d1e1a
--- /dev/null
+++ b/doc/tutorial_pools.dox
@@ -0,0 +1,93 @@
+/**
+@page libtalloc_pools Chapter 5: Memory pools
+
+@section pools Memory pools
+
+Allocation of a new memory is an expensive operation and large programs can
+contain thousands of calls of malloc() for a single computation, where every
+call allocates only a very small amount of the memory. This can result in an
+undesirable slowdown of the application. We can avoid this slowdown by
+decreasing the number of malloc() calls by using a memory pool.
+
+A memory pool is a preallocated memory space with a fixed size. If we need to
+allocate new data we will take the desired amount of the memory from the pool
+instead of requesting a new memory from the system. This is done by creating a
+pointer that points inside the preallocated memory. Such a pool must not be
+reallocated as it would change its location - pointers that were pointing
+inside the pool would become invalid. Therefore, a memory pool requires a very
+good estimate of the required memory space.
+
+The talloc library contains its own implementation of a memory pool. It is
+highly transparent for the programmer. The only thing that needs to be done is
+an initialization of a new pool context using talloc_pool() -
+which can be used in the same way as any other context.
+
+Refactoring of existing code (that uses talloc) to take the advantage of a
+memory pool is quite simple due to the following properties of the pool context:
+
+- if we are allocating data on a pool context, it takes the desired
+  amount of memory from the pool,
+- if the context is a descendant of the pool context, it takes the space
+  from the pool as well,
+- if the pool does not have sufficient portion of memory left, it will
+  create a new non-pool context, leaving the pool intact
+
+@code
+/* allocate 1KiB in a pool */
+TALLOC_CTX *pool_ctx = talloc_pool(NULL, 1024);
+
+/* Take 512B from the pool, 512B is left there */
+void *ptr = talloc_size(pool_ctx, 512);
+
+/* 1024B > 512B, this will create new talloc chunk outside
+   the pool */
+void *ptr2 = talloc_size(ptr, 1024);
+
+/* The pool still contains 512 free bytes
+ * this will take 200B from them. */
+void *ptr3 = talloc_size(ptr, 200);
+
+/* This will destroy context 'ptr3' but the memory
+ * is not freed, the available space in the pool
+ * will increase to 512B. */
+talloc_free(ptr3);
+
+/* This will free memory taken by 'pool_ctx'
+ * and 'ptr2' as well. */
+talloc_free(pool_ctx);
+@endcode
+
+The above given is very convenient, but there is one big issue to be kept in
+mind. If the parent of a talloc pool child is changed to a parent that is
+outside of this pool, the whole pool memory will not be freed until the child is
+freed. For this reason we must be very careful when stealing a descendant of a
+pool context.
+
+@code
+TALLOC_CTX *mem_ctx = talloc_new(NULL);
+TALLOC_CTX *pool_ctx = talloc_pool(NULL, 1024);
+struct foo *foo = talloc(pool_ctx, struct foo);
+
+/* mem_ctx is not in the pool */
+talloc_steal(mem_ctx, foo);
+
+/* pool_ctx is marked as freed but the memory is not
+   deallocated, accessing the pool_ctx again will cause
+   an error */
+talloc_free(pool_ctx);
+
+/* This deallocates the pool_ctx. */
+talloc_free(mem_ctx);
+@endcode
+
+It may often be better to copy the memory we want instead of stealing it to
+avoid this problem. If we do not need to retain the context name (to keep the
+type information), we can use talloc_memdup() to do this.
+
+Copying the memory out of the pool may, however, discard all the performance
+boost given by the pool, depending on the size of the copied memory. Therefore,
+the code should be well profiled before taking this path. In general, the
+golden rule is: if we need to steal from the pool context, we should not
+use a pool context.
+
+*/
diff --git a/doc/tutorial_stealing.dox b/doc/tutorial_stealing.dox
new file mode 100644
index 0000000..67eae1d
--- /dev/null
+++ b/doc/tutorial_stealing.dox
@@ -0,0 +1,55 @@
+/**
+@page libtalloc_stealing Chapter 2: Stealing a context
+
+@section stealing Stealing a context
+
+Talloc has the ability to change the parent of a talloc context to another
+one. This operation is commonly referred to as stealing and it is one of
+the most important actions performed with talloc contexts.
+
+Stealing a context is necessary if we want the pointer to outlive the context it
+is created on. This has many possible use cases, for instance stealing a result
+of a database search to an in-memory cache context, changing the parent of a
+field of a generic structure to a more specific one or vice-versa. The most
+common scenario, at least in Samba, is to steal output data from a function-specific
+context to the output context given as an argument of that function.
+
+@code
+struct foo {
+    char *a1;
+    char *a2;
+    char *a3;
+};
+
+struct bar {
+    char *wurst;
+    struct foo *foo;
+};
+
+struct foo *foo = talloc_zero(ctx, struct foo);
+foo->a1 = talloc_strdup(foo, "a1");
+foo->a2 = talloc_strdup(foo, "a2");
+foo->a3 = talloc_strdup(foo, "a3");
+
+struct bar *bar = talloc_zero(NULL, struct bar);
+/* change parent of foo from ctx to bar */
+bar->foo = talloc_steal(bar, foo);
+
+/* or do the same but assign foo = NULL */
+bar->foo = talloc_move(bar, &foo);
+@endcode
+
+The talloc_move() function is similar to the talloc_steal() function but
+additionally sets the source pointer to NULL.
+
+In general, the source pointer itself is not changed (it only replaces the
+parent in the meta data). But the common usage is that the result is
+assigned to another variable, thus further accessing the pointer from the
+original variable should be avoided unless it is necessary. In this case
+talloc_move() is the preferred way of stealing a context. Additionally sets the
+source pointer to NULL, thus.protects the pointer from being accidentally freed
+and accessed using the old variable after its parent has been changed.
+
+@image html stealing.png
+
+*/
diff --git a/doc/tutorial_threads.dox b/doc/tutorial_threads.dox
new file mode 100644
index 0000000..111bbf5
--- /dev/null
+++ b/doc/tutorial_threads.dox
@@ -0,0 +1,203 @@
+/**
+@page libtalloc_threads Chapter 8: Using threads with talloc
+
+@section Talloc and thread safety
+
+The talloc library is not internally thread-safe, in that accesses
+to variables on a talloc context are not controlled by mutexes or
+other thread-safe primitives.
+
+However, so long as talloc_disable_null_tracking() is called from
+the main thread to disable global variable access within talloc,
+then each thread can safely use its own top level talloc context
+allocated off the NULL context.
+
+For example:
+
+@code
+static void *thread_fn(void *arg)
+{
+	const char *ctx_name = (const char *)arg;
+        /*
+         * Create a new top level talloc hierarchy in
+         * this thread.
+         */
+	void *top_ctx = talloc_named_const(NULL, 0, "top");
+	if (top_ctx == NULL) {
+		return NULL;
+	}
+	sub_ctx = talloc_named_const(top_ctx, 100, ctx_name);
+	if (sub_ctx == NULL) {
+		return NULL;
+	}
+
+	/*
+	 * Do more processing/talloc calls on top_ctx
+	 * and its children.
+	 */
+	......
+
+	talloc_free(top_ctx);
+	return value;
+}
+@endcode
+
+is a perfectly safe use of talloc within a thread.
+
+The problem comes when one thread wishes to move some
+memory allocated on its local top level talloc context
+to another thread. Care must be taken to add data access
+exclusion to prevent memory corruption. One method would
+be to lock a mutex before any talloc call on each thread,
+but this would push the burden of total talloc thread-safety
+on the poor user of the library.
+
+A much easier way to transfer talloced memory between
+threads is by the use of an intermediate, mutex locked,
+intermediate variable.
+
+An example of this is below - taken from test code inside
+the talloc testsuite.
+
+The main thread creates 1000 sub-threads, and then accepts
+the transfer of some thread-talloc'ed memory onto its top
+level context from each thread in turn.
+
+A pthread mutex and condition variable are used to
+synchronize the transfer via the intermediate_ptr
+variable.
+
+@code
+/* Required sync variables. */
+static pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
+static pthread_cond_t condvar = PTHREAD_COND_INITIALIZER;
+
+/* Intermediate talloc pointer for transfer. */
+static void *intermediate_ptr;
+
+/* Subthread. */
+static void *thread_fn(void *arg)
+{
+	int ret;
+	const char *ctx_name = (const char *)arg;
+	void *sub_ctx = NULL;
+	/*
+	 * Do stuff that creates a new talloc hierarchy in
+	 * this thread.
+	 */
+	void *top_ctx = talloc_named_const(NULL, 0, "top");
+	if (top_ctx == NULL) {
+		return NULL;
+	}
+	sub_ctx = talloc_named_const(top_ctx, 100, ctx_name);
+	if (sub_ctx == NULL) {
+		return NULL;
+	}
+
+	/*
+	 * Now transfer a pointer from our hierarchy
+	 * onto the intermediate ptr.
+	 */
+	ret = pthread_mutex_lock(&mtx);
+	if (ret != 0) {
+		talloc_free(top_ctx);
+		return NULL;
+	}
+
+	/* Wait for intermediate_ptr to be free. */
+	while (intermediate_ptr != NULL) {
+		ret = pthread_cond_wait(&condvar, &mtx);
+		if (ret != 0) {
+			talloc_free(top_ctx);
+			return NULL;
+		}
+	}
+
+	/* and move our memory onto it from our toplevel hierarchy. */
+	intermediate_ptr = talloc_move(NULL, &sub_ctx);
+
+	/* Tell the main thread it's ready for pickup. */
+	pthread_cond_broadcast(&condvar);
+	pthread_mutex_unlock(&mtx);
+
+	talloc_free(top_ctx);
+	return NULL;
+}
+
+/* Main thread. */
+
+#define NUM_THREADS 1000
+
+static bool test_pthread_talloc_passing(void)
+{
+	int i;
+	int ret;
+	char str_array[NUM_THREADS][20];
+	pthread_t thread_id;
+	void *mem_ctx;
+
+	/*
+	 * Important ! Null tracking breaks threaded talloc.
+	 * It *must* be turned off.
+	 */
+	talloc_disable_null_tracking();
+
+	/* Main thread toplevel context. */
+	mem_ctx = talloc_named_const(NULL, 0, "toplevel");
+	if (mem_ctx == NULL) {
+		return false;
+	}
+
+	/*
+	 * Spin off NUM_THREADS threads.
+	 * They will use their own toplevel contexts.
+	 */
+	for (i = 0; i < NUM_THREADS; i++) {
+		(void)snprintf(str_array[i],
+				20,
+				"thread:%d",
+				i);
+		if (str_array[i] == NULL) {
+			return false;
+		}
+		ret = pthread_create(&thread_id,
+				NULL,
+				thread_fn,
+				str_array[i]);
+		if (ret != 0) {
+			return false;
+		}
+	}
+
+	/* Now wait for NUM_THREADS transfers of the talloc'ed memory. */
+	for (i = 0; i < NUM_THREADS; i++) {
+		ret = pthread_mutex_lock(&mtx);
+		if (ret != 0) {
+			talloc_free(mem_ctx);
+			return false;
+		}
+
+		/* Wait for intermediate_ptr to have our data. */
+		while (intermediate_ptr == NULL) {
+			ret = pthread_cond_wait(&condvar, &mtx);
+			if (ret != 0) {
+				talloc_free(mem_ctx);
+				return false;
+			}
+		}
+
+		/* and move it onto our toplevel hierarchy. */
+		(void)talloc_move(mem_ctx, &intermediate_ptr);
+
+		/* Tell the sub-threads we're ready for another. */
+		pthread_cond_broadcast(&condvar);
+		pthread_mutex_unlock(&mtx);
+	}
+
+	/* Dump the hierarchy. */
+	talloc_report(mem_ctx, stdout);
+	talloc_free(mem_ctx);
+	return true;
+}
+@endcode
+*/