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<H1 CLASS="title">CUPS Developer Guide</H1>

<P>This developer guide documents the guidelines and processes we use when developing and maintaining CUPS and related software. Our goal is to provide reliable and efficient software and documentation that addresses the needs of our users.</P>

<H2 CLASS="title"><A NAME="COMMUNICATION">Communication</A></H2>

<H3><A NAME="CONTACT">How to Contact the Developers</A></H3>

<P>The <A HREF="http://www.cups.org/newsgroups.php">CUPS
Forums</A> are the primary means of asking questions and
informally discussing issues and feature requests with the CUPS
developers. Table 1 shows the available forums and their
focus:</P>

<DIV CLASS="table"><TABLE SUMMARY="CUPS Forums">
<CAPTION>Table 1: CUPS Forums</CAPTION>
<TR>
	<TH>Forum</TH>
	<TH>Focus/Purpose</TH>
</TR>
<TR>
	<TD>cups.bugs</TD>
	<TD>Discussion of bugs and issues in the CUPS
	software</TD>
</TR>
<TR>
	<TD>cups.commit</TD>
	<TD>Report of all commits to the Subversion repository
	(read-only)</TD>
</TR>
<TR>
	<TD>cups.ddk</TD>
	<TD>Usage and development questions for the CUPS Driver
	Development Kit</TD>
</TR>
<TR>
	<TD>cups.development</TD>
	<TD>Development questions and discussion of new features
	in the CUPS software</TD>
</TR>
<TR>
	<TD>cups.general</TD>
	<TD>Usage questions for the CUPS software</TD>
</TR>
</TABLE></DIV>

<H3><A NAME="SUBMIT">How to Submit a Bug Report or Feature Request</A></H3>

<P>The CUPS "<A HREF="http://www.cups.org/str.php">Bugs &amp;
Features</A>" page provides access to the CUPS <em>software
trouble report</em> database and is the formal way to submit a
bug report or feature request to the CUPS developers. Please
note, however, that we <em>do not</em> provide answers to usage
questions or resolve problems in third-party software on this
page - use the CUPS Forums for that instead.</P>

<P>Unlike discussions that occur on the CUPS Forums, formal bug
reports and feature requests must be acted on by the CUPS
developers. This does not mean that every bug report is resolved
or every feature request is implemented, but we do respond and
keep track of them all for posterity.</P>

<BLOCKQUOTE>Please use the search feature of the Bugs &amp;
Features page before submitting a new bug report or feature
request. If you see an existing report that matches your issue,
please post a message to that report ("I have this issue as
well", "I would also like to see", etc.) rather than submitting a
new report. This helps speed the resolution of your issue by
reducing the CUPS developers' work load.</BLOCKQUOTE>

<H3><A NAME="PATCH">How to Prepare a Patch</A></H3>

<P>When submitting a bug report or feature request, you can
include patch files that resolve the bug or implement the feature
to speed the inclusion of that bug fix or feature in a new CUPS
release. For changes to existing files, we prefer a unified diff
against the current Subversion <VAR>trunk</VAR> branch, which can
be generated easily using the following Subversion command:</P>

<PRE CLASS="command">
svn diff >filename.patch
</PRE>

<P>If you produce a patch using a released source archive, use
one of the following commands instead:</P>

<PRE CLASS="command">
diff -u oldfilename filename >filename.patch

diff -urN olddirectory directory >filename.patch
</PRE>

<P>New files and files with significant changes can be submitted
in their entirety, however that may delay the adoption of your
changes.</P>

<BLOCKQUOTE>Patches and files must conform to the standards outlined in the
"<A HREF="#CODING">Coding Guidelines</A>" and "<A HREF="#MAKEFILES">Makefile
Guidelines</A>" sections in this document. In addition, since Apple Inc.
provides CUPS under multiple licenses, we require that you assign the copyright
for your changes and files to us for inclusion in CUPS.</BLOCKQUOTE>


<H2 CLASS="title"><A NAME="PRACTICES">Software Development Practices</A></H2>

<H3><A NAME="VERSIONS">Version Numbering</A></H3>

<P>CUPS uses a three-part version number separated by periods to
represent the major, minor, and patch release numbers. Major
release numbers indicate large design changes or
backwards-incompatible changes to the CUPS API or CUPS Imaging
API. Minor release numbers indicate new features and other
smaller changes which are backwards-compatible with previous CUPS
releases. Patch numbers indicate bug fixes to the previous
release.</P>

<BLOCKQUOTE>When we talk about compatibility, we are talking
about binary compatibility for public APIs and output format
compatibility for program interfaces. Changes to configuration
file formats or the default behavior of programs are not
generally considered incompatible as the upgrade process can
normally address such changes gracefully.</BLOCKQUOTE>

<P>Production releases use the plain version numbers:</P>

<PRE CLASS="command">
MAJOR.MINOR.PATCH
1.0.0
1.0.1
1.0.2
...
1.1.0
...
1.1.23
1.2.0
1.2.1
...
1.3.0
...
2.0.0
</PRE>

<P>The first production release in a MAJOR.MINOR series (MAJOR.MINOR.0) is
called a feature release. Feature releases are the only releases that may
contain new features. Subsequent production releases in a MAJOR.MINOR series may
only contain bug fixes.</P>

<BLOCKQUOTE>We did not hold to this limitation in the CUPS 1.1 series for a
variety of reasons. Starting with CUPS 1.2, the "no new features in a patch
release" policy has been strictly enforced. The policy has also resulted in
fewer new features (and interactions!) to validate/test in the subsequence
feature releases.</BLOCKQUOTE>

<P>Beta-test releases are identified by appending the letter B to the major and
minor version numbers followed by the beta release number:</P>

<PRE CLASS="command">
MAJOR.MINORbNUMBER
1.2b1
</PRE>

<P>Release candidates are identified by appending the letters RC to the major
and minor version numbers followed by the release candidate number:</P>

<PRE CLASS="command">
MAJOR.MINORrcNUMBER
1.2rc1
</PRE>

<P>Developer snapshots are identified by appending the letters SVN-R to the
major and minor version numbers followed by the revision number:</P>

<PRE CLASS="command">
MAJOR.MINORsvn-rREV
1.2svn-r1234
</PRE>

<P>Beta-test releases, release candidates, and developer snapshots are only
created for new minor releases. Once a production release has been made
(MAJOR.MINOR.0), subsequent patch releases are issues without preliminary beta
or release testing.</P>

<H3>Version Control (Subversion)</H3>

<P>The CUPS source files are managed by the Subversion ("SVN")
software, available at:</P>

<PRE CLASS="command">
<A HREF="http://subversion.tigris.org/" TARGET="_blank">subversion.tigris.org</A>
</PRE>

<P>Source files are "checked in" with each change so that
modifications can be tracked, and each checkin must reference any
applicable STRs. The following format <em>must</em> be used for
commit log messages:</P>

<PRE CLASS="command">
Summary of the change on one line followed by bug number (STR #NNNN)

Detailed list of changes.
</PRE>

<P>Primary development occurs on the <var>trunk</var> branch,
with changes merged back to release branches as needed. Table 2
shows the URLs developers use for the various CUPS subprojects
and branches:</P>

<DIV CLASS="table"><TABLE SUMMARY="CUPS Subversion URLs">
<CAPTION>Table 2: CUPS Subversion URLs</CAPTION>
<TR>
	<TH>URL</TH>
	<TH>Purpose</TH>
</TR>
<TR>
	<TD><A HREF="http://svn.easysw.com/public/cups/trunk/">https://svn.easysw.com/public/cups/trunk/</A></TD>
	<TD>Primary CUPS development branch</TD>
</TR>
<TR>
	<TD><A HREF="http://svn.easysw.com/public/cups/branches/">https://svn.easysw.com/public/cups/branches/</A></TD>
	<TD>CUPS maintenance branches (merge-only)</TD>
</TR>
<TR>
	<TD><A HREF="http://svn.easysw.com/public/cups/tags/">https://svn.easysw.com/public/cups/tags/</A></TD>
	<TD>CUPS release tags (read-only)</TD>
</TR>
<TR>
	<TD><A HREF="http://svn.easysw.com/public/cupsddk/trunk/">https://svn.easysw.com/public/cupsddk/trunk/</A></TD>
	<TD>Primary CUPS DDK development branch</TD>
</TR>
<TR>
	<TD><A HREF="http://svn.easysw.com/public/cupsddk/branches/">https://svn.easysw.com/public/cupsddk/branches/</A></TD>
	<TD>CUPS DDK maintenance branches (merge-only)</TD>
</TR>
<TR>
	<TD><A HREF="http://svn.easysw.com/public/cupsddk/tags/">https://svn.easysw.com/public/cupsddk/tags/</A></TD>
	<TD>CUPS DDK release tags (read-only)</TD>
</TR>
<TR>
	<TD><A HREF="http://svn.easysw.com/public/espgs/trunk/">https://svn.easysw.com/public/espgs/trunk/</A></TD>
	<TD>Primary ESP Ghostscript development branch</TD>
</TR>
<TR>
	<TD><A HREF="http://svn.easysw.com/public/espgs/branches/">https://svn.easysw.com/public/espgs/branches/</A></TD>
	<TD>ESP Ghostscript maintenance branches (merge-only)</TD>
</TR>
<TR>
	<TD><A HREF="http://svn.easysw.com/public/espgs/tags/">https://svn.easysw.com/public/espgs/tags/</A></TD>
	<TD>ESP Ghostscript release tags (read-only)</TD>
</TR>
<TR>
	<TD><A HREF="http://svn.easysw.com/public/windows/trunk/">https://svn.easysw.com/public/windows/trunk/</A></TD>
	<TD>Primary CUPS Windows Driver development branch</TD>
</TR>
<TR>
	<TD><A HREF="http://svn.easysw.com/public/windows/branches/">https://svn.easysw.com/public/windows/branches/</A></TD>
	<TD>CUPS Windows Driver maintenance branches (merge-only)</TD>
</TR>
<TR>
	<TD><A HREF="http://svn.easysw.com/public/windows/tags/">https://svn.easysw.com/public/windows/tags/</A></TD>
	<TD>CUPS Windows Driver release tags (read-only)</TD>
</TR>
</TABLE></DIV>

<P>The branch for a MAJOR.MINOR release are created when the
first production release (MAJOR.MINOR.0) is made using the name
"branch-MAJOR.MINOR". Release tags are created for every beta,
candidate, and production release using the name
"release-MAJOR.MINOR.PATCHbNUMBER",
"release-MAJOR.MINOR.PATCHrcNUMBER", or
"release-MAJOR.MINOR.PATCH", respectively. No release tags are
created for developer snapshots.</P>


<H3>Files and Directories</H3>

<P>File and directory names may not exceed 16 characters in
length to ensure compability with older UNIX filesystems. In
addition, to avoid problems with case-insensitive filesystems, 
you may not use names which differ only by case, for example
"ReadMe" and "README" are not allowed in the same directory.</P>

<P>Source files must be documented and formatted as described in
"<A HREF="#CODING">Coding Requirements</A>". Make files must
follow the guidelines in "<A HREF="#MAKEFILE">Makefile
Guidelines</A>".</P>


<H3>Build System</H3>

<P>The CUPS build system uses <A
HREF="http://www.gnu.org/software/autoconf/">GNU autoconf</A> to
tailor the library to the local operating system. Project files
for major IDEs are also provided for Microsoft
Windows<SUP>&reg;</SUP>. To improve portability, makefiles must
not make use of the unique features offered by <A
HREF="http://www.gnu.org/software/make/">GNU make</A>. See the <A
HREF="#MAKEFILES">Makefile Guidelines</A> section for a
description of the allowed make features and makefile
guidelines.</P>

<P>Additional GNU build programs such as <A
HREF="http://www.gnu.org/software/automake">GNU automake</A> and
<A HREF="http://www.gnu.org/software/libtool">GNU libtool</A>
must not be used. GNU automake produces non-portable makefiles
which depend on GNU-specific extensions, and GNU libtool is not
portable or reliable enough for CUPS.</P>


<H3><A NAME="PACKAGING">Packaging</A></H3>

<P>Source packages are created using the
<VAR>tools/makesrcdist</VAR> script in the Subversion repository.
The script optionally uses a version number argument:</P>

<PRE CLASS="command">
tools/makesrcdist
tools/makesrcdist <I>version</I>
</PRE>

<P>When run with no arguments, the script creates a snapshot of
the current working copy and names it using the highest revision
number in the WC, for example
"/tmp/cups-1.3svn-r1234-source.tar.bz2" and
"/tmp/cups-1.3svn-r1234-source.tar.gz". When run with two
arguments, the script creates a release tag in the repository and
exports that tag, creating the files
"/tmp/cups-<I>version</I>-source.tar.bz2" and
"/tmp/cups-<I>version</I>-source.tar.gz".</P>

<P>Binary packages are not generally distributed by the CUPS
team, however the <VAR>packaging/cups.spec</VAR> and
<VAR>packaging/cups.list</VAR> files may be used to create binary
packages on Linux, Mac OS X, and UNIX. The
<VAR>packaging/cups.spec</VAR> file produces a binary package
using the <CODE>rpmbuild(8)</CODE> software:</P>

<PRE CLASS="command">
rpmbuild -ta cups-<I>version</I>-source.tar.gz
</PRE>

<P>The <VAR>cups.list</VAR> file is generated by the
<VAR>configure</VAR> script and produces binary packages for many
platforms using the <A HREF="http://www.easysw.com/epm/"
TARGET="_blank">EPM</A> software. Table 3 shows the targets that
are available for each type of binary package:</P>

<DIV CLASS="table"><TABLE SUMMARY="Binary Package Targets">
<CAPTION>Table 3: Binary Package Targets</CAPTION>
<TR>
	<TH>Target</TH>
	<TH>Type of Package</TH>
</TR>
<TR>
	<TD>aix</TD>
	<TD>AIX installp</TD>
</TR>
<TR>
	<TD>bsd</TD>
	<TD>*BSD pkg_install</TD>
</TR>
<TR>
	<TD>deb</TD>
	<TD>Debian dpkg</TD>
</TR>
<TR>
	<TD>depot</TD>
	<TD>HP-UX swinstall</TD>
</TR>
<TR>
	<TD>epm</TD>
	<TD>Portable tarball with install script</TD>
</TR>
<TR>
	<TD>inst</TD>
	<TD>IRIX inst/tardist</TD>
</TR>
<TR>
	<TD>osx</TD>
	<TD>Mac OS X Install</TD>
</TR>
<TR>
	<TD>pkg</TD>
	<TD>Solaris pkgadd</TD>
</TR>
<TR>
	<TD>rpm</TD>
	<TD>RPM binary</TD>
</TR>
<TR>
	<TD>setld</TD>
	<TD>Tru64 UNIX setld</TD>
</TR>
<TR>
	<TD>slackware</TD>
	<TD>Slackware install</TD>
</TR>
<TR>
	<TD>swinstall</TD>
	<TD>HP-UX swinstall</TD>
</TR>
<TR>
	<TD>tardist</TD>
	<TD>IRIX inst/tardist</TD>
</TR>
</TABLE></DIV>

<P>Finally, the <VAR>tools/testrpm</VAR> and
<VAR>tools/testosx</VAR> scripts can be used to create binary
packages from the current working copy for testing on Linux and
Mac OS X, respectively:</P>

<PRE CLASS="command">
tools/testrpm
sudo rpm -U /usr/src/redhat/RPMS/i386/cups*.rpm

sudo tools/testosx
open cups.pkg
</PRE>


<H3><A NAME="TESTING">Testing</A></H3>

<P>Software testing is conducted according to the <A
HREF="spec-stp.html">CUPS Software Test Plan</A>. This testing is
automated via the top-level makefile <VAR>test</VAR> target:</P>

<PRE CLASS="command">
make test
</PRE>

<P>The test environment allows for both short-term automated
testing and long-term testing and development without the
automated test script.</P>


<H2 CLASS="title"><A NAME="STR">Trouble Report Processing</A></H2>

<P>A Software Trouble Report ("STR") must be submitted every time
a user or vendor experiences a problem with the CUPS software.
Trouble reports are maintained on the <A
HREF="http://www.cups.org/str.php" TARGET="_blank">Bugs &amp;
Features</A> page with one of the following states:</P>

<OL>

	<LI>STR is closed with complete resolution</LI>

	<LI>STR is closed without resolution</LI>

	<LI>STR is active, waiting on information from submitter</LI>

	<LI>STR is pending with additional information from submitter</LI>

	<LI>STR is newly submitted</LI>

</OL>

<P>Trouble reports are processed using the following steps.</P>

<OL>

<LI>Classification

<P>When a trouble report is received it must be classified at one
of the following priority levels:</P>

<OL>

	<LI>Request for enhancement, e.g. asking for a
	feature

	<LI>Low, e.g. a documentation error or undocumented
	side-effect

	<LI>Moderate, e.g. unable to print a file or unable to
	compile the software

	<LI>High, e.g. unable to print to a printer or key
	functionality not working

	<LI>Critical, e.g. unable to print at all

</OL>

<P>Level 4 and 5 trouble reports must be resolved in the next
software release. Level 2 and 3 trouble reports are scheduled for
resolution in a specific release at the discretion of the release
coordinator. Level 1 trouble reports are scheduled for resolution
in a future feature release.</P>

<P>The scope of the problem is also determined as:</P>

<OL>

	<LI>Specific to a machine or printer

	<LI>Specific to an operating system

	<LI>Applies to all machines, printers, and operating systems

</OL>

<LI>Identification

<P>Once the level and scope of the trouble report is determined
the software sub-system(s) involved with the problem are
determined. This may involve additional communication with the
user or vendor to isolate the problem to a specific cause.</P>

<P>When the sub-system(s) involved have been identified, an
engineer will then determine the change(s) needed and estimate
the time required for the change(s).</P>

<LI>Correction

<P>Corrections are scheduled based upon the severity and
complexity of the problem. Once all changes have been made,
documented, and tested successfully a new software release
snapshot is generated. Additional tests are added as necessary
for proper testing of the changes.</P>

<LI>Notification

<P>The user or vendor is notified when the fix is available or if
the problem was caused by user error.</P>

</OL>


<H2 CLASS="title"><A NAME="RELEASES">Release Management</A></H2>

<P>When testing has been completed successfully, a new source
package is created using the <VAR>tools/makesrcdist</VAR> script.
Three types of releases, beta, candidate, and production, are
created and released to the public using the basic schedule in
Table 4. At least one beta and one release candidate must be
created prior to a production release, and there must be at least
two weeks between the last beta and first candidate and last
candidate and first production release.</P>

<DIV CLASS="table"><TABLE SUMMARY="CUPS Basic Release Schedule">
<CAPTION>Table: CUPS Basic Release Schedule</CAPTION>
<TR>
	<TH>Week</TH>
	<TH>Version</TH>
	<TH>Description</TH>
</TR>
<TR>
	<TD>T-6 weeks</TD>
	<TD>1.2b1</TD>
	<TD>First beta release</TD>
</TR>
<TR>
	<TD>T-5 weeks</TD>
	<TD>1.2b2</TD>
	<TD>Second beta release</TD>
</TR>
<TR>
	<TD>T-3 weeks</TD>
	<TD>1.2rc1</TD>
	<TD>First release candidate</TD>
</TR>
<TR>
	<TD>T-2 weeks</TD>
	<TD>1.2rc2</TD>
	<TD>Second release candidate</TD>
</TR>
<TR>
	<TD>T-0 weeks</TD>
	<TD>1.2.0</TD>
	<TD>Production (feature) release</TD>
</TR>
</TABLE></DIV>


<H2 CLASS="title"><A NAME="CODING">Coding Guidelines</A></H2>

<P>These coding guidelines provide detailed information on source
file formatting and documentation content and must be applied to
all C and C++ source files provided with CUPS. Source code for
other languages should conform to these guidelines as allowed by
the language.</P>

<H3>Source Files</H3>

<P>All source files names shall be 16 characters or less in
length to ensure compatibility with older UNIX filesystems.
Source files containing functions shall have an extension of ".c"
for ANSI C and ".cxx" for C++ source files. All other "include"
files shall have an extension of ".h".</P>

<P>The top of each source file shall contain a header giving the
name of the file, the purpose or nature of the source file, the
copyright and licensing notice, and the functions contained in
the file.  The file name and revision information is provided by
the Subversion "&#36;Id$" tag:</P>

<PRE CLASS="command">
/*
 * "&#36;Id$"
 *
 *   Description of file contents.
 *
 *   Copyright 2010 by Apple Inc.
 *
 *   These coded instructions, statements, and computer programs are the
 *   property of Apple Inc. and are protected by Federal copyright
 *   law.  Distribution and use rights are outlined in the file "LICENSE.txt"
 *   which should have been included with this file.  If this file is
 *   file is missing or damaged, see the license at "http://www.cups.org/".
 *
 * Contents:
 *
 *   function1() - Description 1.
 *   function2() - Description 2.
 *   function3() - Description 3.
 */
</PRE>

<P>For source files that are subject to the Apple OS-Developed
Software exception, the following additional comment should
appear after the contact information:</P>

<PRE CLASS="command">
 *   This file is subject to the Apple OS-Developed Software exception.
</PRE>

<P>The bottom of each source file shall contain a trailer giving
the name of the file using the Subversion "&#36;Id$" tag. The
primary purpose of this is to mark the end of a source file; if
the trailer is missing it is possible that code has been lost
near the end of the file:</P>

<PRE CLASS="command">
/*
 * End of "&#36;Id$".
 */
</PRE>

<H3>Functions</H3>

<P>Functions with a global scope shall have a lowercase prefix
followed by capitalized words ("cupsDoThis", "cupsDoThat",
"cupsDoSomethingElse", etc.) Private global functions shall begin
with a leading underscore ("_cupsDoThis", "_cupsDoThat",
etc.)</P>

<P>Functions with a local scope shall be declared "static" and be
lowercase with underscores between words ("do_this", "do_that",
"do_something_else", etc.)</P>

<P>Each function shall begin with a comment header describing
what the function does, the possible input limits (if any), and
the possible output values (if any), and any special information
needed:</P>

<PRE CLASS="command">
/*
 * 'do_this()' - Compute y = this(x).
 *
 * Notes: none.
 */

static float                            /* O - Inverse power value, 0.0 &lt;= y &lt;= 1.1 */
do_this(float x)                        /* I - Power value (0.0 &lt;= x &lt;= 1.1) */
{
  ...
  return (y);
}
</PRE>

<P>Return/output values are indicated using an "O" prefix, input
values are indicated using the "I" prefix, and values that are
both input and output use the "IO" prefix for the corresponding
in-line comment.</P>

<P>The Mini-XML documentation generator also understands the following
special text in the function description comment:</P>

<UL>

	<LI><CODE>@deprecated@</CODE> - Marks the function as
	deprecated (not recommended for new development and
	scheduled for removal)</LI>

	<LI><CODE>@since CUPS <I>version</I>@</CODE> - Marks the
	function as new in the specified version of CUPS.</LI>

	<LI><CODE>@private@</CODE> - Marks the function as private.</LI>

</UL>

<H3>Variables</H3>

<P>Variables with a global scope shall be capitalized
("ThisVariable", "ThatVariable", "ThisStateVariable", etc.) The
only exception to this rule shall be the CUPS interface library
global variables which must begin with the prefix "cups"
("cupsThisVariable", "cupsThatVariable", etc.) Global variables
shall be replaced by function arguments whenever possible.</P>

<P>Variables with a local scope shall be lowercase with
underscores between words ("this_variable", "that_variable",
etc.) Any local variables shared by functions within a source
file shall be declared "static".</P>

<P>Each variable shall be declared on a separate line and shall
be immediately followed by a comment block describing the
variable:</P>

<PRE CLASS="command">
int this_variable;   /* The current state of this */
int that_variable;   /* The current state of that */
</PRE>

<H3>Types</H3>

<P>All type names shall be lowercase with underscores between
words and "_t" appended to the end of the name
("cups_this_type_t", "cups_that_type_t", etc.) Type names must
start with a prefix, typically "cups" or the name of the program,
to avoid conflicts with system types. Private type names must
start with an underscore ("_cups_this_t", "_cups_that_t",
etc.)</P>

<P>Each type shall have a comment block immediately after the
typedef:</P>

<PRE CLASS="command">
typedef int cups_this_type_t;           /* This type is for CUPS foobar options. */
</PRE>

<H3>Structures</H3>

<P>All structure names shall be lowercase with underscores
between words and "_s" appended to the end of the name
("cups_this_s", "cups_that_s", etc.) Structure names must start
with a prefix, typically "cups" or the name of the program, to
avoid conflicts with system types. Private structure names must
start with an underscore ("_cups_this_s", "_cups_that_s",
etc.)</P>

<P>Each structure shall have a comment block immediately after
the struct and each member shall be documented in accordance with
the variable naming policy above:</P>

<PRE CLASS="command">
struct cups_this_struct_s               /* This structure is for CUPS foobar options. */
{
  int this_member;                      /* Current state for this */
  int that_member;                      /* Current state for that */
};
</PRE>

<H3>Constants</H3>

<P>All constant names shall be uppercase with underscored between
words ("CUPS_THIS_CONSTANT", "CUPS_THAT_CONSTANT", etc.)
Constants must begin with an uppercase prefix, typically "CUPS"
or the program name.</P>

<P>Typed enumerations shall be used whenever possible to allow
for type checking by the compiler.</P>

<P>Comment blocks shall immediately follow each constant:</P>

<PRE CLASS="command">
enum
{
  CUPS_THIS_TRAY,                       /* This tray */
  CUPS_THAT_TRAY                        /* That tray */
};
</PRE>

<H3>Code</H3>

<P>All source code shall utilize block comments within functions
to describe the operations being performed by a group of
statements; avoid putting a comment per line unless absolutely
necessary, and then consider refactoring the code so that it is
not necessary:</P>

<PRE CLASS="command">
/*
 * Clear the state array before we begin...
 */

for (i = 0; i &lt; (sizeof(array) / sizeof(sizeof(array[0])); i ++)
  array[i] = STATE_IDLE;

/*
 * Wait for state changes...
 */

do
{
  for (i = 0; i &lt; (sizeof(array) / sizeof(sizeof(array[0])); i ++)
    if (array[i] != STATE_IDLE)
      break;

  if (i == (sizeof(array) / sizeof(array[0])))
    sleep(1);
} while (i == (sizeof(array) / sizeof(array[0])));
</PRE>

<H3>Indentation</H3>

<P>All code blocks enclosed by brackets shall begin with the
opening brace on a new line. The code then follows starting on a
new line after the brace and is indented 2 spaces. The closing
brace is then placed on a new line following the code at the
original indentation:</P>

<PRE CLASS="command">
{
  int i; /* Looping var */

 /*
  * Process foobar values from 0 to 999...
  */

  for (i = 0; i &lt; 1000; i ++)
  {
    do_this(i);
    do_that(i);
  }
}
</PRE>

<P>Single-line statements following "do", "else", "for", "if",
and "while" shall be indented 2 spaces as well. Blocks of code
in a "switch" block shall be indented 4 spaces after each "case"
and "default" case:</P>

<PRE CLASS="command">
switch (array[i])
{
  case STATE_IDLE :
      do_this(i);
      do_that(i);
      break;
  default :
      do_nothing(i);
      break;
}
</PRE>

<H3>Spacing</H3>

<P>A space shall follow each reserved word ("if", "while", etc.)
Spaces shall not be inserted between a function name and the
arguments in parenthesis.</P>

<H3>Return Values</H3>

<P>Parenthesis shall surround values returned from a function
using "return":</P>

<PRE CLASS="command">
return (CUPS_STATE_IDLE);
</PRE>

<H3>Loops</H3>

<P>Whenever convenient loops should count downward to zero to
improve program performance:</P>

<PRE CLASS="command">
for (i = sizeof(array) / sizeof(array[0]) - 1; i >= 0; i --)
  array[i] = CUPS_STATE_IDLE;
</PRE>

<H2 CLASS="title"><A NAME="MAKEFILES">Makefile Guidelines</A></H2>

<P>The following is a guide to the makefile-based build system
used by CUPS. These standards have been developed over the years
to allow CUPS to be built on as many systems and environments as
possible.</P>

<H3>General Organization</H3>

<P>The CUPS source code is organized functionally into a
top-level makefile, include file, and subdirectories each with
their own makefile and dependencies files. The ".in" files are
template files for the <CODE>autoconf</CODE> software and are
used to generate a static version of the corresponding file.</P>

<H3>Makefile Documentation</H3>

<P>Each make file must start with the standard CUPS header
containing the Subversion "&#36;Id$" keyword, description of the
file, and CUPS copyright and license notice:</P>

<PRE CLASS="command">
#
# "&#36;Id$"
#
#   Makefile for ...
#
#   Copyright 2007 by Apple Inc.
#
#   These coded instructions, statements, and computer programs are the
#   property of Apple Inc. and are protected by Federal copyright
#   law.  Distribution and use rights are outlined in the file "LICENSE.txt"
#   which should have been included with this file.  If this file is
#   file is missing or damaged, see the license at "http://www.cups.org/".
#
</PRE>

<P>The end of each makefile must have a comment saying:</P>

<PRE CLASS="command">
#
# End of "&#36;Id$".
#
</PRE>

<P>The purpose of the trailer is to indicate the end of the
makefile so that truncations are immediately obvious.</P>

<H3>Portable Makefile Construction</H3>

<P>CUPS uses a common subset of make program syntax to ensure
that the software can be compiled "out of the box" on as many
systems as possible. The following is a list of assumptions we
follow when constructing makefiles:</P>

<UL>

	<LI><b>Targets</b>; we assume that the make program
	supports the notion of simple targets of the form
	"name:" that perform tab-indented commands that follow
	the target, e.g.:
	<PRE CLASS="command">
target:
&rarr; target commands</PRE></LI>

	<LI><b>Dependencies</b>; we assume that the make program
	supports recursive dependencies on targets, e.g.:
	<PRE CLASS="command">
target: foo bar
&rarr; target commands

foo: bla
&rarr; foo commands

bar:
&rarr; bar commands

bla:
&rarr; bla commands</PRE></LI>

	<LI><b>Variable Definition</b>; we assume that the make program
	supports variable definition on the command-line or in the makefile
	using the following form:
	<PRE CLASS="command">
name=value</PRE>

	<LI><b>Variable Substitution</b>; we assume that the make program
	supports variable substitution using the following forms:
	<UL>
		<LI><CODE>$(name)</CODE>; substitutes the value of "name",</LI>
		<LI><CODE>($name:.old=.new)</CODE>; substitutes the value of "name"
		with the filename extensions ".old" changed to ".new",</LI>
		<LI><CODE>$(MAKEFLAGS)</CODE>; substitutes the 
		command-line options passed to the program
		without the leading hyphen (-),</LI>
		<LI><CODE>$$</CODE>; substitutes a single <CODE>$</CODE> character,</LI>
		<LI><CODE>$&lt;</CODE>; substitutes the current source file or dependency, and</LI>
		<LI><CODE>$@</CODE>; substitutes the current target name.</LI>
	</UL></LI>

	<LI><b>Suffixes</b>; we assume that the make program
	supports filename suffixes with assumed dependencies, e.g.:
	<PRE CLASS="command">
.SUFFIXES: .c .o
.c.o:
&rarr; $(CC) $(CFLAGS) -o $@ -c $&lt;</PRE></LI>

	<LI><b>Include Files</b>; we assume that the make program
	supports the <CODE>include</CODE> directive, e.g.:
	<PRE CLASS="command">
include ../Makedefs
include Dependencies</PRE></LI>

	<LI><b>Comments</b>; we assume that comments begin with
	a <CODE>#</CODE> character and proceed to the end of the
	current line.</LI>

	<LI><b>Line Length</b>; we assume that there is no
	practical limit to the length of lines.</LI>

	<LI><b>Continuation of long lines</b>; we assume that
	the <CODE>\</CODE> character may be placed at the end of a
	line to concatenate two or more lines in a
	makefile to form a single long line.</LI>

	<LI><b>Shell</b>; we assume a POSIX-compatible shell is
	present on the build system.</LI>

</UL>

<H3>Standard Variables</H3>

<P>The following variables are defined in the "Makedefs" file
generated by the <CODE>autoconf</CODE> software:</P>

<UL>

	<LI><CODE>AR</CODE>; the library archiver command,</LI>

	<LI><CODE>ARFLAGS</CODE>; options for the library archiver command,</LI>

	<LI><CODE>BUILDROOT</CODE>; optional installation prefix,</LI>

	<LI><CODE>MAN1EXT</CODE>; extension for man pages in section 1,</LI>

	<LI><CODE>MAN3EXT</CODE>; extension for man pages in section 3,</LI>

	<LI><CODE>MAN5EXT</CODE>; extension for man pages in section 5,</LI>

	<LI><CODE>MAN7EXT</CODE>; extension for man pages in section 7,</LI>

	<LI><CODE>MAN8DIR</CODE>; subdirectory for man pages in section 8,</LI>

	<LI><CODE>MAN8EXT</CODE>; extension for man pages in section 8,</LI>

	<LI><CODE>CC</CODE>; the C compiler command,</LI>

	<LI><CODE>CFLAGS</CODE>; options for the C compiler command,</LI>

	<LI><CODE>CXX</CODE>; the C++ compiler command,</LI>

	<LI><CODE>CXXFLAGS</CODE>; options for the C++ compiler command,</LI>

	<LI><CODE>DSOCOMMAND</CODE>; the shared library building command,</LI>

	<LI><CODE>DSOFLAGS</CODE>; options for the shared library building command,</LI>

	<LI><CODE>INSTALL</CODE>; the <CODE>install</CODE> command,</LI>

	<LI><CODE>INSTALL_BIN</CODE>; the program installation command,</LI>

	<LI><CODE>INSTALL_DATA</CODE>; the data file installation command,</LI>

	<LI><CODE>INSTALL_DIR</CODE>; the directory installation command,</LI>

	<LI><CODE>INSTALL_LIB</CODE>; the library installation command,</LI>

	<LI><CODE>INSTALL_MAN</CODE>; the documentation installation command,</LI>

	<LI><CODE>INSTALL_SCRIPT</CODE>; the shell script installation command,</LI>

	<LI><CODE>LDFLAGS</CODE>; options for the linker,</LI>

	<LI><CODE>LIBS</CODE>; libraries for all programs,</LI>

	<LI><CODE>LN</CODE>; the <CODE>ln</CODE> command,</LI>

	<LI><CODE>OPTIM</CODE>; common compiler optimization options,</LI>

	<LI><CODE>RM</CODE>; the <CODE>rm</CODE> command,</LI>

	<LI><CODE>SHELL</CODE>; the <CODE>sh</CODE> (POSIX shell) command,</LI>

	<LI><CODE>STRIP</CODE>; the <CODE>strip</CODE> command,</LI>

	<LI><CODE>bindir</CODE>; the binary installation directory,</LI>

	<LI><CODE>datadir</CODE>; the data file installation directory,</LI>

	<LI><CODE>exec_prefix</CODE>; the installation prefix for executable files,</LI>

	<LI><CODE>libdir</CODE>; the library installation directory,</LI>

	<LI><CODE>mandir</CODE>; the man page installation directory,</LI>

	<LI><CODE>prefix</CODE>; the installation prefix for non-executable files, and</LI>

	<LI><CODE>srcdir</CODE>; the source directory.</LI>

</UL>

<H3>Standard Targets</H3>

<P>The following standard targets must be defined in each
makefile:</P>

<UL>

	<LI><CODE>all</CODE>; creates all target programs,
	libraries, and documentation files,</LI>

	<LI><CODE>clean</CODE>; removes all target programs,
	libraries, documentation files, and object files,</LI>

	<LI><CODE>depend</CODE>; generates automatic dependencies
	for any C or C++ source files (also see <A
	HREF="#DEPEND_TARGET">"Dependencies"</A>),</LI>

	<LI><CODE>distclean</CODE>; removes autoconf-generated files
	in addition to those removed by the "clean" target,</LI>

	<LI><CODE>install</CODE>; installs all distribution files in
	their corresponding locations (also see <A
	HREF="#INSTALL_TARGET">"Install/Uninstall Support"</A>), </LI>

	<LI><CODE>uninstall</CODE>; removes all distribution files from
	their corresponding locations (also see <A
	HREF="#INSTALL_TARGET">"Install/Uninstall Support"</A>), and</LI>

</UL>


<H3>Object Files</H3>

<P>Object files (the result of compiling a C or C++ source file)
have the extension ".o".</P>

<H3>Programs</H3>

<P>Program files are the result of linking object files and
libraries together to form an executable file. A typical
program target looks like:</P>

<PRE CLASS="command">
program: $(OBJS)
&rarr; echo Linking $@...
&rarr; $(CC) $(LDFLAGS) -o $@ $(OBJS) $(LIBS)
</PRE>

<H3>Static Libraries</H3>

<P>Static libraries have a prefix of "lib" and the extension
".a". A typical static library target looks like:</P>

<PRE CLASS="command">
libname.a: $(OBJECTS)
&rarr; echo Creating $@...
&rarr; $(RM) $@
&rarr; $(AR) $(ARFLAGS) $@ $(OBJECTS)
&rarr; $(RANLIB) $@
</PRE>

<H3>Shared Libraries</H3>

<P>Shared libraries have a prefix of "lib" and the extension
".dylib", ".sl", ".so", or "_s.a" depending on the operating
system. A typical shared library is composed of several targets
that look like:</P>

<PRE CLASS="command">
libname.so: $(OBJECTS)
&rarr; echo $(DSOCOMMAND) libname.so.$(DSOVERSION) ...
&rarr; $(DSOCOMMAND) libname.so.$(DSOVERSION) $(OBJECTS)
&rarr; $(RM) libname.so libname.so.$(DSOMAJOR)
&rarr; $(LN) libname.so.$(DSOVERSION) libname.so.$(DSOMAJOR)
&rarr; $(LN) libname.so.$(DSOVERSION) libname.so

libname.sl: $(OBJECTS)
&rarr; echo $(DSOCOMMAND) libname.sl.$(DSOVERSION) ...
&rarr; $(DSOCOMMAND) libname.sl.$(DSOVERSION) $(OBJECTS)
&rarr; $(RM) libname.sl libname.sl.$(DSOMAJOR)
&rarr; $(LN) libname.sl.$(DSOVERSION) libname.sl.$(DSOMAJOR)
&rarr; $(LN) libname.sl.$(DSOVERSION) libname.sl

libname.dylib: $(OBJECTS)
&rarr; echo $(DSOCOMMAND) libname.$(DSOVERSION).dylib ...
&rarr; $(DSOCOMMAND) libname.$(DSOVERSION).dylib \
&rarr; &rarr; -install_name $(libdir)/libname.$(DSOMAJOR).dylib \
&rarr; &rarr; -current_version libname.$(DSOVERSION).dylib \
&rarr; &rarr; -compatibility_version $(DSOMAJOR).0 \
&rarr; &rarr; $(OBJECTS) $(LIBS)
&rarr; $(RM) libname.dylib
&rarr; $(RM) libname.$(DSOMAJOR).dylib
&rarr; $(LN) libname.$(DSOVERSION).dylib libname.$(DSOMAJOR).dylib
&rarr; $(LN) libname.$(DSOVERSION).dylib libname.dylib

libname_s.a: $(OBJECTS)
&rarr; echo $(DSOCOMMAND) libname_s.o ...
&rarr; $(DSOCOMMAND) libname_s.o $(OBJECTS) $(LIBS)
&rarr; echo $(LIBCOMMAND) libname_s.a libname_s.o
&rarr; $(RM) $@
&rarr; $(LIBCOMMAND) libname_s.a libname_s.o
&rarr; $(CHMOD) +x libname_s.a
</PRE>


<H3>Dependencies</H3>

<P>Static dependencies are expressed in each makefile following the
target, for example:</P>

<PRE CLASS="command">
foo: bar
</PRE>

<P>Static dependencies shall only be used when it is not
possible to automatically generate them. Automatic dependencies
are stored in a file named "Dependencies" and included at the
end of the makefile. The following "depend" target rule shall be
used to create the automatic dependencies:

<PRE CLASS="command">
depend:
&rarr; $(MAKEDEPEND) -Y -I.. -f Dependencies $(OBJS:.o=.c)
</PRE>

<P>We only regenerate the automatic dependencies on a Linux
system and express any non-Linux dependencies statically in the
makefile.</P>

<H3><A NAME="TARGET_INSTALL">Install/Uninstall Support</A></H3>

<P>All makefiles must contain install and uninstall rules which
install or remove the corresponding software. These rules must
use the <CODE>$(BUILDROOT)</CODE> variable as a prefix to any
installation directory so that CUPS can be installed in a
temporary location for packaging by programs like
<CODE>rpmbuild</CODE>.</P>

<P>The <CODE>$(INSTALL_BIN)</CODE>, <CODE>$(INSTALL_DATA)</CODE>,
<CODE>$(INSTALL_DIR)</CODE>, <CODE>$(INSTALL_LIB)</CODE>,
<CODE>$(INSTALL_MAN)</CODE>, and <CODE>$(INSTALL_SCRIPT)</CODE>
variables must be used when installing files so that the proper
ownership and permissions are set on the installed files.</P>

<P>The <CODE>$(RANLIB)</CODE> command must be run on any static
libraries after installation since the symbol table is
invalidated when the library is copied on some platforms.</P>

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