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* Annotate: (annotate).                 The obsolete annotation interface.

END-INFO-DIR-ENTRY

   Copyright (C) 1994, 1995, 2000, 2001, 2003, 2004, 2005, 2007, 2008,

2009, 2010 Free Software Foundation, Inc.

   Permission is granted to copy, distribute and/or modify this document

under the terms of the GNU Free Documentation License, Version 1.1 or

any later version published by the Free Software Foundation; with no

Invariant Sections, with no Front-Cover Texts, and with no Back-Cover

Texts.  A copy of the license is included in the section entitled "GNU

Free Documentation License".

   This file documents GDB's obsolete annotations.

   Copyright (C) 1994, 1995, 2000, 2001, 2003, 2004, 2005, 2007, 2008,

2009, 2010 Free Software Foundation, Inc.

   Permission is granted to copy, distribute and/or modify this document

under the terms of the GNU Free Documentation License, Version 1.1 or

any later version published by the Free Software Foundation; with no

Invariant Sections, with no Front-Cover Texts, and with no Back-Cover

Texts.  A copy of the license is included in the section entitled "GNU

Free Documentation License".

File: annotate.info,  Node: Top,  Next: Annotations Overview,  Up: (dir)

GDB Annotations

***************

This document describes the obsolete level two annotation interface

implemented in older GDB versions.

* Menu:

* Annotations Overview::  What annotations are; the general syntax.

* Limitations::           Limitations of the annotation interface.

* Migrating to GDB/MI::   Migrating to GDB/MI

* Server Prefix::       Issuing a command without affecting user state.

* Value Annotations::   Values are marked as such.

* Frame Annotations::   Stack frames are annotated.

* Displays::            GDB can be told to display something periodically.

* Prompting::           Annotations marking GDB's need for input.

* Errors::              Annotations for error messages.

* Breakpoint Info::     Information on breakpoints.

* Invalidation::        Some annotations describe things now invalid.

* Annotations for Running::

                        Whether the program is running, how it stopped, etc.

* Source Annotations::  Annotations describing source code.

* Multi-threaded Apps:: An annotation that reports multi-threadedness.

* GNU Free Documentation License::

File: annotate.info,  Node: Annotations Overview,  Next: Limitations,  Prev: Top,  Up: Top

1 What is an Annotation?

************************

To produce obsolete level two annotations, start GDB with the

`--annotate=2' option.

   Annotations start with a newline character, two `control-z'

characters, and the name of the annotation.  If there is no additional

information associated with this annotation, the name of the annotation

is followed immediately by a newline.  If there is additional

information, the name of the annotation is followed by a space, the

additional information, and a newline.  The additional information

cannot contain newline characters.

   Any output not beginning with a newline and two `control-z'

characters denotes literal output from GDB.  Currently there is no need

for GDB to output a newline followed by two `control-z' characters, but

if there was such a need, the annotations could be extended with an

`escape' annotation which means those three characters as output.

   A simple example of starting up GDB with annotations is:

     $ gdb --annotate=2

     GNU GDB 5.0

     Copyright 2000 Free Software Foundation, Inc.

     GDB is free software, covered by the GNU General Public License,

     and you are welcome to change it and/or distribute copies of it

     under certain conditions.

     Type "show copying" to see the conditions.

     There is absolutely no warranty for GDB.  Type "show warranty"

     for details.

     This GDB was configured as "sparc-sun-sunos4.1.3"

     ^Z^Zpre-prompt

     (gdb)

     ^Z^Zprompt

     quit

     ^Z^Zpost-prompt

     $

   Here `quit' is input to GDB; the rest is output from GDB.  The three

lines beginning `^Z^Z' (where `^Z' denotes a `control-z' character) are

annotations; the rest is output from GDB.

File: annotate.info,  Node: Limitations,  Next: Migrating to GDB/MI,  Prev: Annotations Overview,  Up: Top

2 Limitations of the Annotation Interface

*****************************************

The level two annotations mechanism is known to have a number of

technical and architectural limitations.  As a consequence, in 2001,

with the release of GDB 5.1 and the addition of GDB/MI, the annotation

interface was marked as deprecated.

   This chapter discusses the known problems.

2.1 Dependant on CLI output

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

The annotation interface works by interspersing markups with GDB normal

command-line interpreter output.  Unfortunately, this makes the

annotation client dependant on not just the annotations, but also the

CLI output.  This is because the client is forced to assume that

specific GDB commands provide specific information.  Any change to

GDB's CLI output modifies or removes that information and,

consequently, likely breaks the client.

   Since the GDB/MI output is independent of the CLI, it does not have

this problem.

2.2 Scalability

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

The annotation interface relies on value annotations (*note Value

Annotations::) and the display mechanism as a way of obtaining

up-to-date value information.  These mechanisms are not scalable.

   In a graphical environment, where many values can be displayed

simultaneously, a serious performance problem occurs when the client

tries to first extract from GDB, and then re-display, all those values.

The client should instead only request and update the values that

changed.

   The GDB/MI Variable Objects provide just that mechanism.

2.3 Correctness

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

The annotation interface assumes that a variable's value can only be

changed when the target is running.  This assumption is not correct.  A

single assignment to a single variable can result in the entire target,

and all displayed values, needing an update.

   The GDB/MI Variable Objects include a mechanism for efficiently

reporting such changes.

2.4 Reliability

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

The GDB/MI interface includes a dedicated test directory

(`gdb/gdb.mi'), and any addition or fix to GDB/MI must include

testsuite changes.

2.5 Maintainability

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

The annotation mechanism was implemented by interspersing CLI print

statements with various annotations.  As a consequence, any CLI output

change can alter the annotation output.

   Since the GDB/MI output is independent of the CLI, and the GDB/MI is

increasingly implemented independent of the CLI code, its long term

maintenance is much easier.

File: annotate.info,  Node: Migrating to GDB/MI,  Next: Server Prefix,  Prev: Limitations,  Up: Top

3 Migrating to GDB/MI

*********************

By using the `interp mi' command, it is possible for annotation clients

to invoke GDB/MI commands, and hence access the GDB/MI.  By doing this,

existing annotation clients have a migration path from this obsolete

interface to GDB/MI.

File: annotate.info,  Node: Server Prefix,  Next: Value Annotations,  Prev: Migrating to GDB/MI,  Up: Top

4 The Server Prefix

*******************

To issue a command to GDB without affecting certain aspects of the

state which is seen by users, prefix it with `server '.  This means

that this command will not affect the command history, nor will it

affect GDB's notion of which command to repeat if  is pressed on a

line by itself.

   The server prefix does not affect the recording of values into the

value history; to print a value without recording it into the value

history, use the `output' command instead of the `print' command.

File: annotate.info,  Node: Value Annotations,  Next: Frame Annotations,  Prev: Server Prefix,  Up: Top

5 Values

********

_Value Annotations have been removed.  GDB/MI instead provides Variable

Objects._

   When a value is printed in various contexts, GDB uses annotations to

delimit the value from the surrounding text.

   If a value is printed using `print' and added to the value history,

the annotation looks like

     ^Z^Zvalue-history-begin HISTORY-NUMBER VALUE-FLAGS

     HISTORY-STRING

     ^Z^Zvalue-history-value

     THE-VALUE

     ^Z^Zvalue-history-end

where HISTORY-NUMBER is the number it is getting in the value history,

HISTORY-STRING is a string, such as `$5 = ', which introduces the value

to the user, THE-VALUE is the output corresponding to the value itself,

and VALUE-FLAGS is `*' for a value which can be dereferenced and `-'

for a value which cannot.

   If the value is not added to the value history (it is an invalid

float or it is printed with the `output' command), the annotation is

similar:

     ^Z^Zvalue-begin VALUE-FLAGS

     THE-VALUE

     ^Z^Zvalue-end

   When GDB prints an argument to a function (for example, in the output

from the `backtrace' command), it annotates it as follows:

     ^Z^Zarg-begin

     ARGUMENT-NAME

     ^Z^Zarg-name-end

     SEPARATOR-STRING

     ^Z^Zarg-value VALUE-FLAGS

     THE-VALUE

     ^Z^Zarg-end

where ARGUMENT-NAME is the name of the argument, SEPARATOR-STRING is

text which separates the name from the value for the user's benefit

(such as `='), and VALUE-FLAGS and THE-VALUE have the same meanings as

in a `value-history-begin' annotation.

   When printing a structure, GDB annotates it as follows:

     ^Z^Zfield-begin VALUE-FLAGS

     FIELD-NAME

     ^Z^Zfield-name-end

     SEPARATOR-STRING

     ^Z^Zfield-value

     THE-VALUE

     ^Z^Zfield-end

where FIELD-NAME is the name of the field, SEPARATOR-STRING is text

which separates the name from the value for the user's benefit (such as

`='), and VALUE-FLAGS and THE-VALUE have the same meanings as in a

`value-history-begin' annotation.

   When printing an array, GDB annotates it as follows:

     ^Z^Zarray-section-begin ARRAY-INDEX VALUE-FLAGS

where ARRAY-INDEX is the index of the first element being annotated and

VALUE-FLAGS has the same meaning as in a `value-history-begin'

annotation.  This is followed by any number of elements, where is

element can be either a single element:

     `,' WHITESPACE         ; omitted for the first element

     THE-VALUE

     ^Z^Zelt

   or a repeated element

     `,' WHITESPACE         ; omitted for the first element

     THE-VALUE

     ^Z^Zelt-rep NUMBER-OF-REPETITIONS

     REPETITION-STRING

     ^Z^Zelt-rep-end

   In both cases, THE-VALUE is the output for the value of the element

and WHITESPACE can contain spaces, tabs, and newlines.  In the repeated

case, NUMBER-OF-REPETITIONS is the number of consecutive array elements

which contain that value, and REPETITION-STRING is a string which is

designed to convey to the user that repetition is being depicted.

   Once all the array elements have been output, the array annotation is

ended with

     ^Z^Zarray-section-end

File: annotate.info,  Node: Frame Annotations,  Next: Displays,  Prev: Value Annotations,  Up: Top

6 Frames

********

_Value Annotations have been removed.  GDB/MI instead provides a number

of frame commands._

   _Frame annotations are no longer available.  The GDB/MI provides

`-stack-list-arguments', `-stack-list-locals', and `-stack-list-frames'

commands._

   Whenever GDB prints a frame, it annotates it.  For example, this

applies to frames printed when GDB stops, output from commands such as

`backtrace' or `up', etc.

   The frame annotation begins with

     ^Z^Zframe-begin LEVEL ADDRESS

     LEVEL-STRING

where LEVEL is the number of the frame (0 is the innermost frame, and

other frames have positive numbers), ADDRESS is the address of the code

executing in that frame, and LEVEL-STRING is a string designed to

convey the level to the user.  ADDRESS is in the form `0x' followed by

one or more lowercase hex digits (note that this does not depend on the

language).  The frame ends with

     ^Z^Zframe-end

   Between these annotations is the main body of the frame, which can

consist of

   *      ^Z^Zfunction-call

          FUNCTION-CALL-STRING

     where FUNCTION-CALL-STRING is text designed to convey to the user

     that this frame is associated with a function call made by GDB to a

     function in the program being debugged.

   *      ^Z^Zsignal-handler-caller

          SIGNAL-HANDLER-CALLER-STRING

     where SIGNAL-HANDLER-CALLER-STRING is text designed to convey to

     the user that this frame is associated with whatever mechanism is

     used by this operating system to call a signal handler (it is the

     frame which calls the signal handler, not the frame for the signal

     handler itself).

   * A normal frame.

     This can optionally (depending on whether this is thought of as

     interesting information for the user to see) begin with

          ^Z^Zframe-address

          ADDRESS

          ^Z^Zframe-address-end

          SEPARATOR-STRING

     where ADDRESS is the address executing in the frame (the same

     address as in the `frame-begin' annotation, but printed in a form

     which is intended for user consumption--in particular, the syntax

     varies depending on the language), and SEPARATOR-STRING is a string

     intended to separate this address from what follows for the user's

     benefit.

     Then comes

          ^Z^Zframe-function-name

          FUNCTION-NAME

          ^Z^Zframe-args

          ARGUMENTS

     where FUNCTION-NAME is the name of the function executing in the

     frame, or `??' if not known, and ARGUMENTS are the arguments to

     the frame, with parentheses around them (each argument is annotated

     individually as well, *note Value Annotations::).

     If source information is available, a reference to it is then

     printed:

          ^Z^Zframe-source-begin

          SOURCE-INTRO-STRING

          ^Z^Zframe-source-file

          FILENAME

          ^Z^Zframe-source-file-end

          :

          ^Z^Zframe-source-line

          LINE-NUMBER

          ^Z^Zframe-source-end

     where SOURCE-INTRO-STRING separates for the user's benefit the

     reference from the text which precedes it, FILENAME is the name of

     the source file, and LINE-NUMBER is the line number within that

     file (the first line is line 1).

     If GDB prints some information about where the frame is from (which

     library, which load segment, etc.; currently only done on the

     RS/6000), it is annotated with

          ^Z^Zframe-where

          INFORMATION

     Then, if source is to actually be displayed for this frame (for

     example, this is not true for output from the `backtrace'

     command), then a `source' annotation (*note Source Annotations::)

     is displayed.  Unlike most annotations, this is output instead of

     the normal text which would be output, not in addition.

File: annotate.info,  Node: Displays,  Next: Prompting,  Prev: Frame Annotations,  Up: Top

7 Displays

**********

_Display Annotations have been removed.  GDB/MI instead provides

Variable Objects._

   When GDB is told to display something using the `display' command,

the results of the display are annotated:

     ^Z^Zdisplay-begin

     NUMBER

     ^Z^Zdisplay-number-end

     NUMBER-SEPARATOR

     ^Z^Zdisplay-format

     FORMAT

     ^Z^Zdisplay-expression

     EXPRESSION

     ^Z^Zdisplay-expression-end

     EXPRESSION-SEPARATOR

     ^Z^Zdisplay-value

     VALUE

     ^Z^Zdisplay-end

where NUMBER is the number of the display, NUMBER-SEPARATOR is intended

to separate the number from what follows for the user, FORMAT includes

information such as the size, format, or other information about how

the value is being displayed, EXPRESSION is the expression being

displayed, EXPRESSION-SEPARATOR is intended to separate the expression

from the text that follows for the user, and VALUE is the actual value

being displayed.

File: annotate.info,  Node: Prompting,  Next: Errors,  Prev: Displays,  Up: Top

8 Annotation for GDB Input

**************************

When GDB prompts for input, it annotates this fact so it is possible to

know when to send output, when the output from a given command is over,

etc.

   Different kinds of input each have a different "input type".  Each

input type has three annotations: a `pre-' annotation, which denotes

the beginning of any prompt which is being output, a plain annotation,

which denotes the end of the prompt, and then a `post-' annotation

which denotes the end of any echo which may (or may not) be associated

with the input.  For example, the `prompt' input type features the

following annotations:

     ^Z^Zpre-prompt

     ^Z^Zprompt

     ^Z^Zpost-prompt

   The input types are

`prompt'

     When GDB is prompting for a command (the main GDB prompt).

`commands'

     When GDB prompts for a set of commands, like in the `commands'

     command.  The annotations are repeated for each command which is

     input.

`overload-choice'

     When GDB wants the user to select between various overloaded

     functions.

`query'

     When GDB wants the user to confirm a potentially dangerous

     operation.

`prompt-for-continue'

     When GDB is asking the user to press return to continue.  Note:

     Don't expect this to work well; instead use `set height 0' to

     disable prompting.  This is because the counting of lines is buggy

     in the presence of annotations.

File: annotate.info,  Node: Errors,  Next: Breakpoint Info,  Prev: Prompting,  Up: Top

9 Errors

********

     ^Z^Zquit

   This annotation occurs right before GDB responds to an interrupt.

     ^Z^Zerror

   This annotation occurs right before GDB responds to an error.

   Quit and error annotations indicate that any annotations which GDB

was in the middle of may end abruptly.  For example, if a

`value-history-begin' annotation is followed by a `error', one cannot

expect to receive the matching `value-history-end'.  One cannot expect

not to receive it either, however; an error annotation does not

necessarily mean that GDB is immediately returning all the way to the

top level.

   A quit or error annotation may be preceded by

     ^Z^Zerror-begin

   Any output between that and the quit or error annotation is the error

message.

   Warning messages are not yet annotated.

File: annotate.info,  Node: Breakpoint Info,  Next: Invalidation,  Prev: Errors,  Up: Top

10 Information on Breakpoints

*****************************

_Breakpoint Annotations have been removed.  GDB/MI instead provides

breakpoint commands._

   The output from the `info breakpoints' command is annotated as

follows:

     ^Z^Zbreakpoints-headers

     HEADER-ENTRY

     ^Z^Zbreakpoints-table

where HEADER-ENTRY has the same syntax as an entry (see below) but

instead of containing data, it contains strings which are intended to

convey the meaning of each field to the user.  This is followed by any

number of entries.  If a field does not apply for this entry, it is

omitted.  Fields may contain trailing whitespace.  Each entry consists

of:

     ^Z^Zrecord

     ^Z^Zfield 0

     NUMBER

     ^Z^Zfield 1

     TYPE

     ^Z^Zfield 2

     DISPOSITION

     ^Z^Zfield 3

     ENABLE

     ^Z^Zfield 4

     ADDRESS

     ^Z^Zfield 5

     WHAT

     ^Z^Zfield 6

     FRAME

     ^Z^Zfield 7

     CONDITION

     ^Z^Zfield 8

     IGNORE-COUNT

     ^Z^Zfield 9

     COMMANDS

   Note that ADDRESS is intended for user consumption--the syntax

varies depending on the language.

   The output ends with

     ^Z^Zbreakpoints-table-end

File: annotate.info,  Node: Invalidation,  Next: Annotations for Running,  Prev: Breakpoint Info,  Up: Top

11 Invalidation Notices

***********************

The following annotations say that certain pieces of state may have

changed.

`^Z^Zframes-invalid'

     The frames (for example, output from the `backtrace' command) may

     have changed.

`^Z^Zbreakpoints-invalid'

     The breakpoints may have changed.  For example, the user just

     added or deleted a breakpoint.

File: annotate.info,  Node: Annotations for Running,  Next: Source Annotations,  Prev: Invalidation,  Up: Top

12 Running the Program

**********************

When the program starts executing due to a GDB command such as `step'

or `continue',

     ^Z^Zstarting

   is output.  When the program stops,

     ^Z^Zstopped

   is output.  Before the `stopped' annotation, a variety of

annotations describe how the program stopped.

`^Z^Zexited EXIT-STATUS'

     The program exited, and EXIT-STATUS is the exit status (zero for

     successful exit, otherwise nonzero).

`^Z^Zsignalled'

     The program exited with a signal.  After the `^Z^Zsignalled', the

     annotation continues:

          INTRO-TEXT

          ^Z^Zsignal-name

          NAME

          ^Z^Zsignal-name-end

          MIDDLE-TEXT

          ^Z^Zsignal-string

          STRING

          ^Z^Zsignal-string-end

          END-TEXT

     where NAME is the name of the signal, such as `SIGILL' or

     `SIGSEGV', and STRING is the explanation of the signal, such as

     `Illegal Instruction' or `Segmentation fault'.  INTRO-TEXT,

     MIDDLE-TEXT, and END-TEXT are for the user's benefit and have no

     particular format.

`^Z^Zsignal'

     The syntax of this annotation is just like `signalled', but GDB is

     just saying that the program received the signal, not that it was

     terminated with it.

`^Z^Zbreakpoint NUMBER'

     The program hit breakpoint number NUMBER.

`^Z^Zwatchpoint NUMBER'

     The program hit watchpoint number NUMBER.

File: annotate.info,  Node: Source Annotations,  Next: Multi-threaded Apps,  Prev: Annotations for Running,  Up: Top

13 Displaying Source

********************

The following annotation is used instead of displaying source code:

     ^Z^Zsource FILENAME:LINE:CHARACTER:MIDDLE:ADDR

   where FILENAME is an absolute file name indicating which source

file, LINE is the line number within that file (where 1 is the first

line in the file), CHARACTER is the character position within the file

(where 0 is the first character in the file) (for most debug formats

this will necessarily point to the beginning of a line), MIDDLE is

`middle' if ADDR is in the middle of the line, or `beg' if ADDR is at

the beginning of the line, and ADDR is the address in the target

program associated with the source which is being displayed.  ADDR is

in the form `0x' followed by one or more lowercase hex digits (note

that this does not depend on the language).

File: annotate.info,  Node: Multi-threaded Apps,  Next: GNU Free Documentation License,  Prev: Source Annotations,  Up: Top

14 Multi-threaded Applications

******************************

The following annotations report thread related changes of state.

`^Z^Znew-thread'

     This annotation is issued once for each thread that is created

     apart from the main thread, which is not reported.

`^Z^Zthread-changed'

     The selected thread has changed.  This may occur at the request of

     the user with the `thread' command, or as a result of execution,

     e.g., another thread hits a breakpoint.

File: annotate.info,  Node: GNU Free Documentation License,  Prev: Multi-threaded Apps,  Up: Top

15 GNU Free Documentation License

*********************************

                      Version 1.2, November 2002

     Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.

     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

     Everyone is permitted to copy and distribute verbatim copies

     of this license document, but changing it is not allowed.

  0. PREAMBLE

     The purpose of this License is to make a manual, textbook, or other

     functional and useful document "free" in the sense of freedom: to

     assure everyone the effective freedom to copy and redistribute it,

     with or without modifying it, either commercially or

     noncommercially.  Secondarily, this License preserves for the

     author and publisher a way to get credit for their work, while not

     being considered responsible for modifications made by others.

     This License is a kind of "copyleft", which means that derivative

     works of the document must themselves be free in the same sense.

     It complements the GNU General Public License, which is a copyleft

     license designed for free software.

     We have designed this License in order to use it for manuals for

     free software, because free software needs free documentation: a

     free program should come with manuals providing the same freedoms

     that the software does.  But this License is not limited to

     software manuals; it can be used for any textual work, regardless

     of subject matter or whether it is published as a printed book.

     We recommend this License principally for works whose purpose is

     instruction or reference.

  1. APPLICABILITY AND DEFINITIONS

     This License applies to any manual or other work, in any medium,

     that contains a notice placed by the copyright holder saying it

     can be distributed under the terms of this License.  Such a notice

     grants a world-wide, royalty-free license, unlimited in duration,

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     A "Modified Version" of the Document means any work containing the

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     A "Secondary Section" is a named appendix or a front-matter section

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     The "Invariant Sections" are certain Secondary Sections whose

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     this License, but only as regards disclaiming warranties: any other

     implication that these Warranty Disclaimers may have is void and

     has no effect on the meaning of this License.

  2. VERBATIM COPYING

     You may copy and distribute the Document in any medium, either

     commercially or noncommercially, provided that this License, the

     copyright notices, and the license notice saying this License

     applies to the Document are reproduced in all copies, and that you

     add no other conditions whatsoever to those of this License.  You

     may not use technical measures to obstruct or control the reading

     or further copying of the copies you make or distribute.  However,

     you may accept compensation in exchange for copies.  If you

     distribute a large enough number of copies you must also follow

     the conditions in section 3.

     You may also lend copies, under the same conditions stated above,

     and you may publicly display copies.

  3. COPYING IN QUANTITY

     If you publish printed copies (or copies in media that commonly

     have printed covers) of the Document, numbering more than 100, and

     the Document's license notice requires Cover Texts, you must

     enclose the copies in covers that carry, clearly and legibly, all

     these Cover Texts: Front-Cover Texts on the front cover, and

     Back-Cover Texts on the back cover.  Both covers must also clearly

     and legibly identify you as the publisher of these copies.  The

     front cover must present the full title with all words of the

     title equally prominent and visible.  You may add other material

     on the covers in addition.  Copying with changes limited to the

     covers, as long as they preserve the title of the Document and

     satisfy these conditions, can be treated as verbatim copying in

     other respects.

     If the required texts for either cover are too voluminous to fit

     legibly, you should put the first ones listed (as many as fit

     reasonably) on the actual cover, and continue the rest onto

     adjacent pages.

     If you publish or distribute Opaque copies of the Document

     numbering more than 100, you must either include a

     machine-readable Transparent copy along with each Opaque copy, or

     state in or with each Opaque copy a computer-network location from

     which the general network-using public has access to download

     using public-standard network protocols a complete Transparent

     copy of the Document, free of added material.  If you use the

     latter option, you must take reasonably prudent steps, when you

     begin distribution of Opaque copies in quantity, to ensure that

     this Transparent copy will remain thus accessible at the stated

     location until at least one year after the last time you

     distribute an Opaque copy (directly or through your agents or

     retailers) of that edition to the public.

     It is requested, but not required, that you contact the authors of

     the Document well before redistributing any large number of

     copies, to give them a chance to provide you with an updated

     version of the Document.

  4. MODIFICATIONS

     You may copy and distribute a Modified Version of the Document

     under the conditions of sections 2 and 3 above, provided that you

     release the Modified Version under precisely this License, with

     the Modified Version filling the role of the Document, thus

     licensing distribution and modification of the Modified Version to

     whoever possesses a copy of it.  In addition, you must do these

     things in the Modified Version:

       A. Use in the Title Page (and on the covers, if any) a title

          distinct from that of the Document, and from those of

          previous versions (which should, if there were any, be listed

          in the History section of the Document).  You may use the

          same title as a previous version if the original publisher of

          that version gives permission.

       B. List on the Title Page, as authors, one or more persons or

          entities responsible for authorship of the modifications in

          the Modified Version, together with at least five of the

          principal authors of the Document (all of its principal

          authors, if it has fewer than five), unless they release you

          from this requirement.

       C. State on the Title page the name of the publisher of the

          Modified Version, as the publisher.

       D. Preserve all the copyright notices of the Document.

       E. Add an appropriate copyright notice for your modifications

          adjacent to the other copyright notices.

       F. Include, immediately after the copyright notices, a license

          notice giving the public permission to use the Modified

          Version under the terms of this License, in the form shown in

          the Addendum below.

       G. Preserve in that license notice the full lists of Invariant

          Sections and required Cover Texts given in the Document's

          license notice.

       H. Include an unaltered copy of this License.

       I. Preserve the section Entitled "History", Preserve its Title,

          and add to it an item stating at least the title, year, new

          authors, and publisher of the Modified Version as given on

          the Title Page.  If there is no section Entitled "History" in

          the Document, create one stating the title, year, authors,

          and publisher of the Document as given on its Title Page,

          then add an item describing the Modified Version as stated in

          the previous sentence.

       J. Preserve the network location, if any, given in the Document

          for public access to a Transparent copy of the Document, and

          likewise the network locations given in the Document for

          previous versions it was based on.  These may be placed in

          the "History" section.  You may omit a network location for a

          work that was published at least four years before the

          Document itself, or if the original publisher of the version

          it refers to gives permission.

       K. For any section Entitled "Acknowledgements" or "Dedications",

          Preserve the Title of the section, and preserve in the

          section all the substance and tone of each of the contributor

          acknowledgements and/or dedications given therein.

       L. Preserve all the Invariant Sections of the Document,

          unaltered in their text and in their titles.  Section numbers

          or the equivalent are not considered part of the section

          titles.