Index: doc/tex/asterisk.tex
===================================================================
--- doc/tex/asterisk.tex	(revision 137185)
+++ doc/tex/asterisk.tex	(working copy)
@@ -136,6 +136,8 @@
   \input{phoneprov.tex}
 
 \chapter{Development}
+  \section{Coding guidelines}
+  \input{coding-guidelines.tex}
   \section{Backtrace}
   \input{backtrace.tex}
 
@@ -153,7 +155,6 @@
 %See http://www.asterisk.org/developers for more information
 %
 %callfiles.txt      Asterisk callfiles using instruction
-%CODING-GUIDELINES  Guidelines for developers
 %externalivr.txt    Documentation of the protocol used in externalivr()
 %modules.txt        How Asterisk modules work
 %datastores.txt     About channel data stores
Index: doc/tex/coding-guidelines.tex
===================================================================
--- doc/tex/coding-guidelines.tex	(revision 0)
+++ doc/tex/coding-guidelines.tex	(revision 0)
@@ -0,0 +1,1117 @@
+\subsection{Introduction}
+
+This section gives some basic indication on how the asterisk code
+is structured. The first part covers the structure and style of
+individual files. The second part (TO BE COMPLETED) covers the
+overall code structure and the build architecture.
+
+Please read it to the end to understand in detail how the asterisk
+code is organized, and to know how to extend asterisk or contribute
+new code.
+
+We are looking forward to your contributions to Asterisk - the 
+Open Source PBX! As Asterisk is a large and in some parts very
+time-sensitive application, the code base needs to conform to
+a common set of coding rules so that many developers can enhance
+and maintain the code. Code also needs to be reviewed and tested
+so that it works and follows the general architecture and guide-
+lines, and is well documented.
+
+Asterisk is published under a dual-licensing scheme by Digium.
+To be accepted into the codebase, all non-trivial changes must be
+licensed to Digium. For more information, see the electronic license
+agreement on \url{http://bugs.digium.com/}.
+
+\subsection{Contributing patches}
+
+Patches should be in the form of a unified (-u) diff, made from a checkout
+from subversion.
+
+\begin{astlisting}
+\begin{verbatim}
+	/usr/src/asterisk$ svn diff > mypatch
+\end{verbatim}
+\end{astlisting}
+
+If you would like to only include changes to certain files in the patch, you
+can list them in the "svn diff" command:
+
+\begin{astlisting}
+\begin{verbatim}
+/usr/src/asterisk$ svn diff somefile.c someotherfile.c > mypatch
+\end{verbatim}
+\end{astlisting}
+
+\subsection{Coding rules}
+
+\subsubsection{General rules}
+
+\begin{itemize}
+\item All code, filenames, function names and comments must be in ENGLISH.
+
+\item Don't annotate your changes with comments like \verb|/* JMG 4/20/04 */|;
+  Comments should explain what the code does, not when something was changed
+  or who changed it. If you have done a larger contribution, make sure
+  that you are added to the \textbf{CREDITS} file.
+
+\item Don't make unnecessary whitespace changes throughout the code.
+  If you make changes, submit them to the tracker as separate patches
+  that only include whitespace and formatting changes.
+
+\item Don't use C++ type (//) comments.
+
+\item Try to match the existing formatting of the file you are working on.
+
+\item Use spaces instead of tabs when aligning in-line comments or \verb|#defines| (this makes 
+  your comments aligned even if the code is viewed with another tabsize)
+\end{itemize}
+
+\subsubsection{File structure and header inclusion}
+
+Every C source file should start with a proper copyright
+and a brief description of the content of the file.
+Following that, you should immediately put the following lines:
+
+\begin{astlisting}
+\begin{verbatim}
+#include "asterisk.h"
+ASTERISK_FILE_VERSION(__FILE__, "$Revision: 127363 $")
+\end{verbatim}
+\end{astlisting}
+
+\begin{description}
+\item[asterisk.h] resolves OS and compiler dependencies for the basic 
+set of unix functions (data types, system calls, basic I/O libraries) and the basic Asterisk APIs.
+
+\item[ASTERISK\_FILE\_VERSION()] stores in the executable information about the file.   
+\end{description}
+
+Next, you should \verb|#include| extra headers according to the functionality
+that your file uses or implements. For each group of functions that
+you use there is a common header, which covers OS header dependencies
+and defines the 'external' API of those functions (the equivalent
+of 'public' members of a class).  As an example:
+
+\begin{itemize}
+
+\item    \textbf{asterisk/module.h}
+        if you are implementing a module, this should be included in one
+        of the files that are linked with the module.
+
+\item    \textbf{asterisk/io.h}
+        access to extra file I/O functions (stat, fstat, playing with
+        directories etc)
+
+\item    \textbf{asterisk/network.h}
+        basic network I/O - all of the socket library, select/poll,
+        and asterisk-specific (usually either thread-safe or reentrant
+        or both) functions to play with socket addresses.
+
+\item    \textbf{asterisk/app.h}
+        parsing of application arguments
+
+\item    \textbf{asterisk/channel.h}
+        \verb|struct ast_channel| and functions to manipulate it
+\end{itemize}
+
+For more information look at the headers in include/asterisk/ .
+These files are usually self-sufficient, i.e. they recursively \verb|#include|
+all the extra headers they need.
+
+The equivalent of 'private' members of a class are either directly in
+the C source file, or in files named \verb|asterisk/mod_*.h| to make it clear
+that they are not for inclusion by generic code.
+
+Keep the number of header files small by not including them unnecessarily.
+Don't cut\&paste list of header files from other sources, but only include
+those you really need. Apart from obvious cases (e.g. module.h which
+is almost always necessary) write a short comment next to each \verb|#include| to
+explain why you need it.
+
+\subsubsection{Declaration of functions and variables}
+
+\begin{itemize}
+\item Do not declare variables mid-block (e.g. like recent GNU compilers support)
+  since it is harder to read and not portable to GCC 2.95 and others.
+
+\item Functions and variables that are not intended to be used outside the module
+  must be declared static.
+
+\item When reading integer numeric input with \verb|scanf()| (or variants), do \textbf{NOT} use '%i'
+  unless you specifically want to allow non-base-10 input; '%d' is always a better
+  choice, since it will not silently turn numbers with leading zeros into base-8.
+
+\item Strings that are coming from input should not be used as a first argument to
+  a formatted *\verb|printf| function.
+\end{itemize}
+
+\subsubsection{Use the internal API}
+
+\begin{itemize}
+\item Make sure you are aware of the string and data handling functions that exist
+  within Asterisk to enhance portability and in some cases to produce more
+  secure and thread-safe code. Check utils.c/utils.h for these.
+
+\item If you need to create a detached thread, use the \verb|ast_pthread_create_detached()|
+  normally or \verb|ast_pthread_create_detached_background()| for a thread with a smaller
+  stack size.  This reduces the replication of the code to handle the \verb|pthread_attr_t|
+  structure.
+\end{itemize}
+
+\subsubsection{Code formatting}
+
+Roughly, Asterisk code formatting guidelines are generally equivalent to the 
+following:
+
+\begin{astlisting}
+\begin{verbatim}
+# indent -i4 -ts4 -br -brs -cdw -lp -ce -nbfda -npcs -nprs -npsl -nbbo -saf -sai -saw -cs -l90 foo.c
+
+this means in verbose:
+ -i4:    indent level 4
+ -ts4:   tab size 4
+ -br:    braces on if line
+ -brs:   braces on struct decl line
+ -cdw:   cuddle do while
+ -lp:    line up continuation below parenthesis
+ -ce:    cuddle else
+ -nbfda: dont break function decl args
+ -npcs:  no space after function call names
+ -nprs:  no space after parentheses
+ -npsl:  dont break procedure type
+ -saf:   space after for
+ -sai:   space after if
+ -saw:   space after while
+ -cs:    space after cast
+ -ln90:  line length 90 columns
+\end{verbatim}
+\end{astlisting}
+
+Function calls and arguments should be spaced in a consistent way across
+the codebase.
+
+\begin{astlisting}
+\begin{description}
+	\item[GOOD:] foo(arg1, arg2);
+	\item[BAD:]  foo(arg1,arg2);
+	\item[BAD:]  foo (arg1, arg2);
+	\item[BAD:]  foo( arg1, arg2 );
+	\item[BAD:]  foo(arg1, arg2,arg3);
+\end{description}
+\end{astlisting}
+
+Don't treat keywords (\verb|if|, \verb|while|, \verb|do|, \verb|return|) as if they were functions;
+leave space between the keyword and the expression used (if any). For \verb|return|,
+don't even put parentheses around the expression, since they are not
+required.
+
+There is no shortage of whitespace characters :-) Use them when they make
+the code easier to read. For example:
+
+\begin{astlisting}
+\begin{verbatim}
+	for (str=foo;str;str=str->next)
+\end{verbatim}
+\end{astlisting}
+
+
+is harder to read than
+
+\begin{astlisting}
+\begin{verbatim}
+	for (str = foo; str; str = str->next)
+\end{verbatim}
+\end{astlisting}
+
+Following are examples of how code should be formatted.
+
+\begin{itemize}
+
+\item Functions
+
+\begin{astlisting}
+\begin{verbatim}
+	int foo(int a, char *s)
+	{
+	        return 0;
+	}
+\end{verbatim}
+\end{astlisting}
+
+\item If statements
+
+\begin{astlisting}
+\begin{verbatim}
+if (foo) {
+        bar();
+} else {
+        blah();
+}
+\end{verbatim}
+\end{astlisting}
+
+\item Case statements
+
+\begin{astlisting}
+\begin{verbatim}
+switch (foo) {
+case BAR:
+        blah();
+        break;
+case OTHER:
+        other();
+        break;
+}
+\end{verbatim}
+\end{astlisting}
+
+\item \textbf{No} nested statements without braces
+
+	\begin{astlisting}
+	\begin{verbatim}
+	for (x = 0; x < 5; x++)
+	        if (foo) 
+	               if (bar)
+	                       baz();
+
+	\end{verbatim}
+	\end{astlisting}
+instead do:
+	\begin{astlisting}
+	\begin{verbatim}
+	for (x = 0; x < 5; x++) {
+	        if (foo) {
+	                if (bar) {
+	                         baz();
+	                }
+	        }
+	}
+	\end{verbatim}
+	\end{astlisting}
+
+\item Always use braces around the statements following an \verb|if|/\verb|for|/\verb|while| construct,
+even if not strictly necessary, as it reduces future possible problems.
+Don't build code like this:
+
+	\begin{astlisting}
+	\begin{verbatim}
+	if (foo) {
+	        /* .... 50 lines of code ... */
+	} else {
+	        result = 0;
+	        return;
+	}
+	\end{verbatim}
+	\end{astlisting}
+
+Instead, try to minimize the number of lines of code that need to be
+indented, by only indenting the shortest case of the \verb|if|
+statement, like so:
+
+	\begin{astlisting}
+	\begin{verbatim}
+	if (!foo) {
+	        result = 0;
+	        return;
+	}
+
+	.... 50 lines of code ....
+	\end{verbatim}
+	\end{astlisting}
+
+When this technique is used properly, it makes functions much easier to read
+and follow, especially those with more than one or two 'setup' operations
+that must succeed for the rest of the function to be able to execute.
+
+\item Labels/goto are acceptable
+
+Proper use of this technique may occasionally result in the need for a
+label/goto combination so that error/failure conditions can exit the
+function while still performing proper cleanup. This is not a bad thing!
+Use of goto in this situation is encouraged, since it removes the need
+for excess code indenting without requiring duplication of cleanup code.
+       
+\item Never use an uninitialized variable
+
+Make sure you never use an uninitialized variable.  The compiler will 
+usually warn you if you do so. However, do not go too far the other way,
+and needlessly initialize variables that do not require it. If the first
+time you use a variable in a function is to store a value there, then
+initializing it at declaration is pointless, and will generate extra
+object code and data in the resulting binary with no purpose. When in doubt,
+trust the compiler to tell you when you need to initialize a variable;
+if it does not warn you, initialization is not needed.
+
+\item Do not cast \verb|void *|
+
+Do not explicitly cast \verb|void *| into any other type, nor should you cast any
+other type into \verb|void *|. Implicit casts to/from \verb|void *| are explicitly
+allowed by the C specification. This means the results of \verb|malloc()|, \verb|calloc()|,
+\verb|alloca()|, and similar functions do not \textbf{ever} need to be cast to a specific
+type, and when you are passing a pointer to (for example) a callback function
+that accepts a \verb|void *| you do not need to cast into that type.
+
+\end{itemize}
+
+\subsubsection{Function naming}
+
+All public functions (those not marked \verb|static|), must be named \verb|ast_<something>()|
+and have a descriptive name.
+
+As an example, suppose you wanted to take a local function \verb|find_feature|, defined
+as static in a file, and used only in that file, and make it public, and use it
+in other files. You will have to remove the "static" declaration and define a 
+prototype in an appropriate header file (usually in include/asterisk). A more
+specific name should be given, such as \verb|ast_find_call_feature()|.
+
+\subsubsection{Variable function argument parsing}
+
+Functions with a variable amount of arguments need a 'sentinel' when called.
+Newer GNU C compilers are fine if you use NULL for this. Older versions (pre 4)
+don't like this.
+You should use the constant SENTINEL.
+This one is defined in \verb|include/asterisk/compiler.h|
+
+\subsubsection{Variable naming}
+
+\begin{description}
+\item[Global variables]
+
+Name global variables (or local variables when you have a lot of them or
+are in a long function) something that will make sense to aliens who
+find your code in 100 years.  All variable names should be in lower 
+case, except when following external APIs or specifications that normally
+use upper- or mixed-case variable names; in that situation, it is
+preferable to follow the external API/specification for ease of
+understanding.
+
+Make some indication in the name of global variables which represent
+options that they are in fact intended to be global.
+ e.g.: \linebreak
+\verb|static char global_something[80]|
+
+\item[Don't use un-necessary typedef's]
+
+Don't use \verb|typedef| just to shorten the amount of typing; there is no substantial
+benefit in this:
+
+\begin{astlisting}
+\begin{verbatim}
+struct foo { int bar; }; typedef struct foo foo_t;
+\end{verbatim}
+\end{astlisting}
+
+In fact, don't use 'variable type' suffixes at all; it's much preferable to
+just type \verb|struct foo| rather than \verb|foo_s|.
+
+\item [Use enums instead of \#define where possible]
+
+Use enums rather than long lists of \verb|#define|-d numeric constants when possible;
+this allows structure members, local variables and function arguments to
+be declared as using the enum's type. For example:
+
+\begin{astlisting}
+\begin{verbatim}
+enum option {
+  OPT_FOO = 1,
+  OPT_BAR = 2,
+  OPT_BAZ = 4,
+};
+
+static enum option global_option;
+
+static handle_option(const enum option opt)
+{
+  ...
+}
+\end{verbatim}
+\end{astlisting}
+
+Note: The compiler will \textbf{not} force you to pass an entry from the enum
+as an argument to this function; this recommendation serves only to make
+the code clearer and somewhat self-documenting. In addition, when using
+switch/case blocks that switch on enum values, the compiler will warn
+you if you forget to handle one or more of the enum values, which can be
+handy.
+\end{description}
+
+\subsubsection{String handling}
+
+Don't use strncpy for copying whole strings; it does not guarantee that the
+output buffer will be null-terminated. Use \verb|ast_copy_string()| instead, which
+is also slightly more efficient (and allows passing the actual buffer
+size, which makes the code clearer).
+
+Don't use \verb|ast_copy_string()| (or any length-limited copy function) for copying
+fixed (known at compile time) strings into buffers, if the buffer is something
+that has been allocated in the function doing the copying. In that case, you
+know at the time you are writing the code whether the buffer is large enough
+for the fixed string or not, and if it's not, your code won't work anyway!
+Use \verb|strcpy()| for this operation, or directly set the first two characters
+of the buffer if you are just trying to store a one-character string in the
+buffer. If you are trying to 'empty' the buffer, just store a single
+\verb|NULL| character (\verb|\0|) in the first byte of the buffer; nothing else is
+needed, and any other method is wasteful.
+
+In addition, if the previous operations in the function have already
+determined that the buffer in use is adequately sized to hold the string
+you wish to put into it (even if you did not allocate the buffer yourself),
+use a direct \verb|strcpy()|, as it can be inlined and optimized to simple
+processor operations, unlike \verb|ast_copy_string()|.
+
+\subsubsection{Use of functions}
+
+\begin{itemize}
+
+\item When making applications, always \verb|ast_strdupa(data)| to a local pointer if
+you intend to parse the incoming data string.
+
+\begin{verbatim}
+	if (data)
+	        mydata = ast_strdupa(data);
+\end{verbatim}
+
+\item Use the argument parsing macros to declare arguments and parse them.
+
+\begin{astlisting}
+\begin{verbatim}
+        AST_DECLARE_APP_ARGS(args,
+                AST_APP_ARG(arg1);
+                AST_APP_ARG(arg2);
+                AST_APP_ARG(arg3);
+        );
+        parse = ast_strdupa(data);
+        AST_STANDARD_APP_ARGS(args, parse);
+\end{verbatim}
+\end{astlisting}
+
+\item Create generic code!
+
+If you do the same or a similar operation more than one time, make it a
+function or macro.
+
+Make sure you are not duplicating any functionality already found in an
+API call somewhere.  If you are duplicating functionality found in 
+another static function, consider the value of creating a new API call 
+which can be shared.
+
+\end{itemize}
+
+\subsubsection{Handling of pointers and allocations}
+
+\begin{itemize}
+
+\item Dereference or localize pointers
+Always dereference or localize pointers to things that are not yours like
+channel members in a channel that is not associated with the current 
+thread and for which you do not have a lock.
+
+\begin{astlisting}
+\begin{verbatim}
+          channame = ast_strdupa(otherchan->name);
+\end{verbatim}
+\end{astlisting}
+
+\item Use const on pointer arguments if possible
+
+Use const on pointer arguments which your function will not be modifying, as this 
+allows the compiler to make certain optimizations. In general, use \verb|const|
+on any argument that you have no direct intention of modifying, as it can
+catch logic/typing errors in your code when you use the argument variable
+in a way that you did not intend.
+
+\item Do not create your own linked list code - reuse!
+
+As a common example of this point, make an effort to use the lockable
+linked-list macros found in \verb|include/asterisk/linkedlists.h|. They are
+efficient, easy to use and provide every operation that should be
+necessary for managing a singly-linked list (if something is missing,
+let us know!). Just because you see other open-coded list implementations
+in the source tree is no reason to continue making new copies of
+that code... There are also a number of common string manipulation
+and timeval manipulation functions in \verb|asterisk/strings.h| and 
+\textbf{asterisk/time.h}; use them when possible.
+
+\item Avoid needless allocations
+
+Avoid needless \verb|malloc()|, \verb|strdup()| calls. If you only need the value in
+the scope of your function try \verb|ast_strdupa()| or declare structs on the
+stack and pass a pointer to them. However, be careful to \textbf{never} call
+\verb|alloca()|, \verb|ast_strdupa()| or similar functions in the argument list
+of a function you are calling; this can cause very strange stack
+arrangements and produce unexpected behavior.
+
+\item Allocations for structures
+
+When allocating/zeroing memory for a structure, use code like this:
+
+\begin{astlisting}
+\begin{verbatim}
+struct foo *tmp;
+
+...
+
+tmp = ast_calloc(1, sizeof(*tmp));
+\end{verbatim}
+\end{astlisting}
+
+Avoid the combination of \verb|ast_malloc()| and \verb|memset()|.  Instead, always use
+\verb|ast_calloc()|. This will allocate and zero the memory in a single operation. 
+In the case that uninitialized memory is acceptable, there should be a comment
+in the code that states why this is the case.
+
+Using \verb|sizeof(*tmp)| instead of \verb|sizeof(struct foo)| eliminates duplication of the 
+'struct foo' identifier, which makes the code easier to read and also ensures 
+that if it is copy-and-pasted it won't require as much editing.
+
+The \verb|ast_*| family of functions for memory allocation are functionally the same.
+They just add an Asterisk log error message in the case that the allocation
+fails for some reason. This eliminates the need to generate custom messages
+throughout the code to log that this has occurred.
+
+\item String Duplications
+
+The functions strdup and strndup can \textbf{not} accept a NULL argument. This results
+in having code like this:
+
+\begin{astlisting}
+\begin{verbatim}
+        if (str)
+                newstr = strdup(str);
+        else
+                newstr = NULL;
+\end{verbatim}
+\end{astlisting}
+
+However, the \verb|ast_strdup()| and \verb|ast_strdupa()| functions will happily accept a NULL
+argument without generating an error.  The same code can be written as:
+
+\begin{astlisting}
+\begin{verbatim}
+         newstr = ast_strdup(str);
+\end{verbatim}
+\end{astlisting}
+
+Furthermore, it is unnecessary to have code that \verb|malloc()|/\verb|calloc()|'s for the length
+of a string (+1 for the terminating \verb|\0|) and then using strncpy to copy the
+copy the string into the resulting buffer.  This is the exact same thing as
+using \verb|ast_strdup()|.
+
+\end{itemize}
+
+\subsubsection{CLI Commands}
+
+New CLI commands should be named using the module's name, followed by a verb
+and then any parameters that the command needs. For example:
+
+\begin{astlisting}
+\begin{verbatim}
+*CLI> iax2 show peer <peername>
+\end{verbatim}
+\end{astlisting}
+\textbf{not}
+\begin{astlisting}
+\begin{verbatim}
+*CLI> show iax2 peer <peername>
+\end{verbatim}
+\end{astlisting}
+
+\subsubsection{New dialplan applications/functions}
+
+There are two methods of adding functionality to the Asterisk
+dialplan: applications and functions. Applications (found generally in
+the apps/ directory) should be collections of code that interact with
+a channel and/or user in some significant way. Functions (which can be
+provided by any type of module) are used when the provided
+functionality is simple... getting/retrieving a value, for
+example. Functions should also be used when the operation is in no way
+related to a channel (a computation or string operation, for example).
+
+Applications are registered and invoked using the
+\verb|ast_register_application()| function}; see the \textbf{apps/app\_skel.c} file for an
+example.
+
+Functions are registered using \verb|struct ast_custom_function|
+structures and the \verb|ast_custom_function_register()| function.
+
+
+\subsubsection{Doxygen API Documentation Guidelines}
+
+When writing Asterisk API documentation the following format should be
+followed. Do not use the javadoc style.
+
+\begin{astlisting}
+\begin{verbatim}
+/*!
+ * \brief Do interesting stuff.
+ *
+ * \param thing1 interesting parameter 1.
+ * \param thing2 interesting parameter 2.
+ *
+ * This function does some interesting stuff.
+ *
+ * \retval zero on success
+ * \retval -1 on error.
+ */
+int ast_interesting_stuff(int thing1, int thing2)
+{
+        return 0;
+}
+\end{verbatim}
+\end{astlisting}
+
+Notice the use of the \verb|\param|, \verb|\brief|, and \verb|\return| constructs.  These should be
+used to describe the corresponding pieces of the function being documented.
+Also notice the blank line after the last \verb|\param| directive.  All doxygen
+comments must be in one \verb|/*! */| block.  If the function or struct does not need
+an extended description it can be left out.
+
+Please make sure to review the doxygen manual and make liberal use of the \verb|\a|,
+\verb|\code|, \verb|c|, \verb|\b|, \verb|\note|, \verb|\li| and \verb|\e| 
+modifiers as appropriate.
+
+When documenting a \verb|static| function or an internal structure in a module,
+use the \verb|\internal| modifier to ensure that the resulting documentation
+explicitly says 'for internal use only'.
+
+Structures should be documented as follows.
+
+\begin{astlisting}
+\begin{verbatim}
+/*!
+ * \brief A very interesting structure.
+ */
+struct interesting_struct
+{
+        /*! \brief A data member. */
+        int member1;
+
+        int member2; /*!< \brief Another data member. */
+}
+\end{verbatim}
+\end{astlisting}
+
+Note that \verb|/*! */| blocks document the construct immediately following them
+unless they are written, \verb|/*!< */|, in which case they document the construct
+preceding them.
+
+It is very much preferred that documentation is not done inline, as done in
+the previous example for member2.  The first reason for this is that it tends
+to encourage extremely brief, and often pointless, documentation since people
+try to keep the comment from making the line extremely long.  However, if you
+insist on using inline comments, please indent the documentation with spaces!
+That way, all of the comments are properly aligned, regardless of what tab
+size is being used for viewing the code.
+
+\subsubsection{Finishing up before you submit your code}
+
+\begin{enumerate}
+
+\item Look at the code once more
+
+When you achieve your desired functionality, make another few refactor
+passes over the code to optimize it.
+
+\item Read the patch
+
+Before submitting a patch, \textbf{read} the actual patch file to be sure that 
+all the changes you expect to be there are, and that there are no 
+surprising changes you did not expect. During your development, that
+part of Asterisk may have changed, so make sure you compare with the
+latest CVS.
+
+\item Listen to advice
+
+If you are asked to make changes to your patch, there is a good chance
+the changes will introduce bugs, check it even more at this stage.
+Also remember that the bug marshal or co-developer that adds comments 
+is only human, they may be in error :-)
+
+\item Optimize, optimize, optimize
+
+If you are going to reuse a computed value, save it in a variable
+instead of recomputing it over and over.  This can prevent you from 
+making a mistake in subsequent computations, making it easier to correct
+if the formula has an error and may or may not help optimization but 
+will at least help readability.
+
+Just an example (so don't over analyze it, that'd be a shame):
+
+\begin{astlisting}
+\begin{verbatim}
+const char *prefix = "pre";	
+const char *postfix = "post";
+char *newname;
+char *name = "data";
+
+if (name && (newname = alloca(strlen(name) + strlen(prefix) + strlen(postfix) + 3)))
+       snprintf(newname, strlen(name) + strlen(prefix) + strlen(postfix) + 3, "%s/%s/%s", 
+		prefix, name, postfix);
+\end{verbatim}
+\end{astlisting}
+
+...vs this alternative:
+
+\begin{astlisting}
+\begin{verbatim}
+const char *prefix = "pre";
+const char *postfix = "post";
+char *newname;
+char *name = "data";
+int len = 0;
+
+if (name && (len = strlen(name) + strlen(prefix) + strlen(postfix) + 3) && 
+	(newname = alloca(len)))
+        snprintf(newname, len, "%s/%s/%s", prefix, name, postfix);
+\end{verbatim}
+\end{astlisting}
+
+\end{enumerate}
+
+\subsubsection{Creating new manager events?}
+
+If you create new AMI events, please read manager.txt. Do not re-use
+existing headers for new purposes, but please re-use existing headers
+for the same type of data.
+
+Manager events that signal a status are required to have one
+event name, with a status header that shows the status.
+The old style, with one event named "ThisEventOn" and another named
+"ThisEventOff", is no longer approved.
+
+Check manager.txt for more information on manager and existing
+headers. Please update this file if you add new headers.
+
+\subsubsection{Locking in Asterisk}
+
+\begin{enumerate}
+\item[A.] Locking Fundamentals
+
+Asterisk is a heavily multithreaded application.  It makes extensive
+use of locking to ensure safe access to shared resources between
+different threads.
+
+When more that one lock is involved in a given code path, there is the
+potential for deadlocks.  A deadlock occurs when a thread is stuck
+waiting for a resource that it will never acquire.  Here is a classic
+example of a deadlock:
+
+\begin{center}
+\begin{tabular}{ c | c }
+Thread 1 & Thread 2 \\
+\hline
+Holds Lock A & Holds Lock B \\
+Waiting for Lock B & Waiting for Lock A \\
+\end{tabular}
+\end{center}
+
+In this case, there is a deadlock between threads 1 and 2.
+This deadlock would have been avoided if both threads had
+agreed that one must acquire Lock A before Lock B.
+
+In general, the fundamental rule for dealing with multiple locks is
+
+\begin{quote}
+    an order \textbf{must} be established to acquire locks, and then all threads
+    must respect that order when acquiring locks.
+\end{quote}
+
+\item[A.1.] Establishing a locking order
+
+Because any ordering for acquiring locks is ok, one could establish
+the rule arbitrarily, e.g. ordering by address, or by some other criterion.
+The main issue, though, is defining an order that
+\begin{itemize}
+  \item is easy to check at runtime;
+  \item reflects the order in which the code executes.
+\end{itemize}
+As an example, if a data structure B is only accessible through a
+data structure A, and both require locking, then the natural order
+is locking first A and then B.
+As another example, if we have some unrelated data structures to
+be locked in pairs, then a possible order can be based on the address
+of the data structures themselves.
+
+\item[B.] Minding the boundary between channel drivers and the Asterisk core
+
+The \#1 cause of deadlocks in Asterisk is by not properly following the
+locking rules that exist at the boundary between Channel Drivers and
+the Asterisk core.  The Asterisk core allocates an \verb|ast_channel|, and
+Channel Drivers allocate "technology specific private data" (PVT) that is
+associated with an \verb|ast_channel|.  Typically, both the \verb|ast_channel| and
+PVT have their own lock.  There are \textbf{many}
+code paths that require both objects to be locked.
+
+The locking order in this situation is the following:
+\begin{enumerate}
+    \item ast\_channel
+    \item PVT
+\end{enumerate}
+
+Channel Drivers implement the \verb|ast_channel_tech interface| to provide a
+channel implementation for Asterisk.  Most of the \verb|channel_tech|
+interface callbacks are called with the associated \verb|ast_channel|
+locked.  When accessing technology specific data, the PVT can be locked
+directly because the locking order is respected.
+
+\item[C.] Preventing lock ordering reversals.
+
+There are some code paths which make it extremely difficult to
+respect the locking order.
+Consider for example the following situation:
+
+\begin{enumerate}
+    \item A message comes in over the "network"
+    \item The Channel Driver (CD) monitor thread receives the message
+    \item The CD associates the message with a PVT and locks the PVT
+    \item While processing the message, the CD must do something that requires
+       locking the ast\_channel associated to the PVT
+\end{enumerate}
+
+This is the point that must be handled carefully.
+The following psuedo-code
+
+\begin{astlisting}
+\begin{verbatim}
+      unlock(pvt);
+      lock(ast_channel);
+      lock(pvt);
+\end{verbatim}
+\end{astlisting}
+
+is \textbf{not} correct for two reasons:
+
+\begin{enumerate}
+
+\item first and foremost, unlocking the PVT means that other threads
+   can acquire the lock and believe it is safe to modify the
+   associated data. When reacquiring the lock, the original thread
+   might find unexpected changes in the protected data structures.
+   This essentially means that the original thread must behave as if
+   the lock on the pvt was not held, in which case it could have
+   released it itself altogether;
+
+\item Asterisk uses the so called "recursive" locks, which allow a thread
+   to issue a \verb|lock()| call multiple times on the same lock. Recursive
+   locks count the number of calls, and they require an equivalent
+   number of \verb|unlock()| to be actually released.
+
+   For this reason, just calling \verb|unlock()| once does not guarantee that the
+   lock is actually released -- it all depends on how many times \verb|lock()|
+   was called before.
+\end{enumerate}
+
+An alternative, but still incorrect, construct is widely used in
+the asterisk code to try and improve the situation:
+
+\begin{astlisting}
+\begin{verbatim}
+     while (trylock(ast_channel) == FAILURE) {
+          unlock(pvt);
+          usleep(1); /* yield to other threads */
+          lock(pvt);
+      }
+\end{verbatim}
+\end{astlisting}
+
+Here the \verb|trylock()| is non blocking, so we do not deadlock if the \verb|ast_channel|
+is already locked by someone else: in this case, we try to unlock the PVT
+(which happens only if the PVT lock counter is 1), yield the CPU to
+give other threads a chance to run, and then acquire the lock again.
+
+This code is not correct for two reasons:
+\begin{enumerate}
+
+  \item Same as in the previous example, it releases the lock when the thread
+     probably did not expect it;
+  \item If the PVT lock counter is greater than 1 we will not
+     really release the lock on the PVT. We might be lucky and have the
+     other contender actually release the lock itself, and so we will "win"
+     the race, but if both contenders have their lock counts > 1 then
+     they will loop forever (basically replacing deadlock with livelock).
+\end{enumerate}
+
+Another variant of this code is the following:
+
+\begin{astlisting}
+\begin{verbatim}
+    if (trylock(ast_channel) == FAILURE) {
+        unlock(pvt);
+        lock(ast_channel);
+        lock(pvt);
+    }
+\end{verbatim}
+\end{astlisting}
+
+which has the same issues as the \verb|while(trylock...)| code, but just
+deadlocks instead of looping forever in case of lock \verb|counts > 1|.
+
+The deadlock/livelock could be in principle spared if one had an
+\verb|unlock_all()| function that calls unlock as many times as needed to
+actually release the lock, and reports the count. Then we could do:
+
+\begin{astlisting}
+\begin{verbatim}
+    if (trylock(ast_channel) == FAILURE) {
+        n = unlock_all(pvt);
+        lock(ast_channel)
+        while (n-- > 0) lock(pvt);
+    }
+\end{verbatim}
+\end{astlisting}
+
+The issue with unexpected unlocks remains, though.
+
+\item[D.] Locking multiple channels.
+
+The next situation to consider is what to do when you need a lock on
+multiple ast\_channels (or multiple unrelated data structures).
+
+If we are sure that we do not hold any of these locks, then the
+following construct is sufficient:
+
+\begin{astlisting}
+\begin{verbatim}
+         lock(MIN(chan1, chan2));
+         lock(MAX(chan1, chan2));
+\end{verbatim}
+\end{astlisting}
+
+That type of code would follow an established locking order of always
+locking the channel that has a lower address first.  Also keep in mind
+that to use this construct for channel locking, one would have to go
+through the entire codebase to ensure that when two channels are locked,
+this locking order is used.
+
+   However, if we enter the above section of code with some lock held
+(which would be incorrect using non-recursive locks, but is completely
+legal using recursive mutexes) then the locking order is not guaranteed
+anymore because it depends on which locks we already hold. So we have
+to go through the same tricks used for the channel+PVT case.
+
+\item[E.] Recommendations
+
+As you can see from the above discussion, getting locking right is all
+but easy. So please follow these recommendations when using locks:
+
+\begin{itemize}
+
+\item Use locks only when really necessary
+
+    Please try to use locks only when strictly necessary, and only for
+    the minimum amount of time required to run critical sections of code.
+    A common use of locks in the current code is to protect a data structure
+    from being released while you use it.
+    With the use of reference-counted objects (astobj2) this should not be
+    necessary anymore.
+
+\item Do not sleep while holding a lock
+
+    If possible, do not run any blocking code while holding a lock,
+    because you will also block other threads trying to access the same
+    lock. In many cases, you can hold a reference to the object to avoid
+    that it is deleted while you sleep, perhaps set a flag in the object
+    itself to report other threads that you have some pending work to
+    complete, then release and acquire the lock around the blocking path,
+    checking the status of the object after you acquire the lock to make
+    sure that you can still perform the operation you wanted to.
+
+\item Try not to exploit the 'recursive' feature of locks.
+
+    Recursive locks are very convenient when coding, as you don't have to
+    worry, when entering a section of code, whether or not you already
+    hold the lock -- you can just protect the section with a lock/unlock
+    pair and let the lock counter track things for you.
+
+       But as you have seen, exploiting the features of recursive locks
+    make it a lot harder to implement proper deadlock avoidance strategies.
+    So please try to analyse your code and determine statically whether you
+    already hold a lock when entering a section of code.
+
+       If you need to call some function \verb|foo()| with and without a lock held,
+    you could define two function as below:
+
+	\begin{astlisting}
+	\begin{verbatim}
+        foo_locked(...) {
+            ... do something, assume lock held
+        }
+
+        foo(...) {
+            lock(xyz)
+            ret = foo_locked(...)
+            unlock(xyz)
+            return ret;
+        }
+	\end{verbatim}
+	\end{astlisting}
+
+    and call them according to the needs.
+
+\item Document locking rules.
+
+    Please document the locking order rules are documented for every
+    lock introduced into Asterisk.  This is done almost nowhere in the
+    existing code.  However, it will be expected to be there for newly
+    introduced code.  Over time, this information should be added for
+    all of the existing lock usage.
+\end{itemize}
+
+\end{enumerate}
+
+
+\subsection{Build Architecture}
+
+The asterisk build architecture relies on autoconf to detect the
+system configuration, and on a locally developed tool (menuselect) to
+select build options and modules list, and on gmake to do the build.
+
+The first step, usually to be done soon after a checkout, is running
+"./configure", which will store its findings in two files:
+
+\begin{description}
+    \item[include/asterisk/autoconfig.h]
+
+	contains C macros, normally \verb|#define HAVE_FOO| or \verb|HAVE_FOO_H| ,
+	for all functions and headers that have been detected at build time.
+	These are meant to be used by C or C++ source files.
+
+    \item[makeopts]
+
+	contains variables that can be used by Makefiles.
+	In addition to the usual CC, LD, ... variables pointing to
+	the various build tools, and prefix, includedir ... which are
+	useful for generic compiler flags, there are variables
+	for each package detected.
+	These are normally of the form \verb|FOO_INCLUDE=... FOO_LIB=...|
+	\verb|FOO_DIR=...| indicating, for each package, the useful libraries
+	and header files. 
+\end{description}
+
+The next step is to run "make menuselect", to extract the dependencies existing
+between files and modules, and to store build options.
+menuselect produces two files, both to be read by the Makefile:
+
+\begin{description}
+    \item[menuselect.makeopts]
+
+	Contains for each subdirectory a list of modules that must be
+	excluded from the build, plus some additional informatiom.
+
+    \item[menuselect.makedeps]
+
+	Contains, for each module, a list of packages it depends on.
+	For each of these packages, we can collect the relevant INCLUDE
+	and LIB files from makeopts. This file is based on information
+	in the .c source code files for each module.
+\end{description}
+
+The top level Makefile is in charge of setting up the build environment,
+creating header files with build options, and recursively invoking the
+subdir Makefiles to produce modules and the main executable.
+
+The sources are split in multiple directories, more or less divided by
+module type (apps/ channels/ funcs/ res/ ...) or by function, for the main
+binary (main/ pbx/).
+
+