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<col class="field-name" /> |
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<col class="field-body" /> |
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<tbody valign="top"> |
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<tr class="field"><th class="field-name">GLEP:</th><td class="field-body">29</td> |
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</tr> |
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<tr class="field"><th class="field-name">Title:</th><td class="field-body">USE flag groups</td> |
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</tr> |
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<tr class="field"><th class="field-name">Version:</th><td class="field-body">1.4</td> |
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</tr> |
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<tr class="field"><th class="field-name">Author:</th><td class="field-body">Ciaran McCreesh <ciaranm at gentoo.org></td> |
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</tr> |
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<tr class="field"><th class="field-name">Last-Modified:</th><td class="field-body"><a class="reference" href="http://www.gentoo.org/cgi-bin/viewcvs/xml/htdocs/proj/en/glep/glep-0029.txt?cvsroot=gentoo">2004/10/25 16:57:09</a></td> |
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</tr> |
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<tr class="field"><th class="field-name">Status:</th><td class="field-body">Draft</td> |
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</tr> |
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<tr class="field"><th class="field-name">Type:</th><td class="field-body">Standards Track</td> |
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</tr> |
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<tr class="field"><th class="field-name">Content-Type:</th><td class="field-body"><a class="reference" href="glep-0012.html">text/x-rst</a></td> |
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</tr> |
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<tr class="field"><th class="field-name">Created:</th><td class="field-body">19-August-2004</td> |
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</tr> |
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<tr class="field"><th class="field-name">Post-Date:</th><td class="field-body">21-August-2004, 18-October-2004, 25-October-2004</td> |
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</tr> |
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</tbody> |
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</table> |
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<hr /> |
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<div class="contents topic" id="contents"> |
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<p class="topic-title first"><a name="contents">Contents</a></p> |
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<ul class="simple"> |
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<li><a class="reference" href="#abstract" id="id7" name="id7">Abstract</a></li> |
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<li><a class="reference" href="#motivation" id="id8" name="id8">Motivation</a></li> |
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<li><a class="reference" href="#specification" id="id9" name="id9">Specification</a><ul> |
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<li><a class="reference" href="#group-specification" id="id10" name="id10">Group Specification</a></li> |
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<li><a class="reference" href="#group-descriptions" id="id11" name="id11">Group Descriptions</a></li> |
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<li><a class="reference" href="#using-groups" id="id12" name="id12">Using Groups</a></li> |
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<li><a class="reference" href="#issues-with-flags-and-groups" id="id13" name="id13">Issues with -flags and -@GROUPS</a></li> |
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<li><a class="reference" href="#adding-new-groups" id="id14" name="id14">Adding New Groups</a></li> |
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</ul> |
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</li> |
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<li><a class="reference" href="#rationale" id="id15" name="id15">Rationale</a></li> |
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<li><a class="reference" href="#reference-implementation" id="id16" name="id16">Reference Implementation</a></li> |
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<li><a class="reference" href="#backwards-compatibility" id="id17" name="id17">Backwards Compatibility</a></li> |
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<li><a class="reference" href="#references" id="id18" name="id18">References</a></li> |
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<li><a class="reference" href="#copyright" id="id19" name="id19">Copyright</a></li> |
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</ul> |
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</div> |
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<div class="section" id="abstract"> |
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<h1><a class="toc-backref" href="#id7" name="abstract">Abstract</a></h1> |
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<p>Currently, USE flags must be selected on a one-by-one basis, making it |
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time-consuming to set up make.conf appropriately for a machine's role.</p> |
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</div> |
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<div class="section" id="motivation"> |
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<h1><a class="toc-backref" href="#id8" name="motivation">Motivation</a></h1> |
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<p>Many packages have optional support for other packages (for example, the |
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Vim text editor can optionally support perl, python and ruby |
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interpreters). In Gentoo, these optional dependencies can be selected by |
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the user using USE flags. This allows a system appropriate for a given |
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environment to be built -- a server, for example, should not typically |
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have an X11 server or sound support, whereas both would be desirable on |
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most desktop systems.</p> |
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<p>With several hundred USE flags available, deciding upon which USE flags to |
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enable and which to disable can take a long time. Although the default USE |
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flag settings are reasonable, they are clearly not appropriate for every |
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system. In addition, using "-<em>" to disable all default USE flags can be |
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risky as certain USE flags should not generally be turned off. This GLEP |
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proposes a mechanism for grouping USE flags to simplify selection and to |
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make USE="-</em>" less dangerous.</p> |
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</div> |
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<div class="section" id="specification"> |
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<h1><a class="toc-backref" href="#id9" name="specification">Specification</a></h1> |
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<div class="section" id="group-specification"> |
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<h2><a class="toc-backref" href="#id10" name="group-specification">Group Specification</a></h2> |
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<p>A group shall consist of one or more tokens. Each token may be a USE flag, |
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a -USE flag, a reference to another group or a negative reference to |
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another group.</p> |
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<p>These groups are defined in <tt class="literal"><span class="pre">${PORTDIR}/profiles/use.groups</span></tt>. It is |
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proposed that uppercase names only are used for groups to keep them |
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visually distinct from normal USE flags (almost all USE flags are |
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lowercase), although this should not been forced programmatically. The |
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file should be similar in format to the existing use.* files. In the |
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following, <tt class="literal"><span class="pre">SOME_GROUP</span></tt> and <tt class="literal"><span class="pre">OTHER_GROUP</span></tt> are group names, and |
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<tt class="literal"><span class="pre">flag1</span></tt> through <tt class="literal"><span class="pre">flag5</span></tt> are USE flag names:</p> |
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<pre class="literal-block"> |
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SOME_GROUP flag1 flag2 flag3 |
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OTHER_GROUP flag2 flag4 |
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</pre> |
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<p>Groups may recursively include other groups. For consistency with GLEP 23 |
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<a class="footnote-reference" href="#id4" id="id1" name="id1">[1]</a>, it is proposed that group names have their name prefixed with an |
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'at' symbol (@):</p> |
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<pre class="literal-block"> |
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GROUP1 flag1 |
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GROUP2 flag2 flag3 @GROUP1 |
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GROUP3 flag4 |
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GROUP4 @GROUP2 @GROUP3 flag5 |
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</pre> |
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<p>The same flag may end up being in a particular group more than once:</p> |
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<pre class="literal-block"> |
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GROUP1 flag1 flag2 |
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GROUP2 flag2 flag3 |
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GROUP3 @GROUP1 @GROUP2 flag3 flag4 |
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</pre> |
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<p>As with similar files, comments may be included. Lines which begin with a |
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hash symbol (#) are comments.</p> |
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<pre class="literal-block"> |
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# This is a comment |
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FOO bar baz fnord |
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</pre> |
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<p>Users may create their own groups using <tt class="literal"><span class="pre">/etc/portage/use.groups</span></tt>. This |
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file overrides the profile settings in the case of duplicates.</p> |
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<p>It should be legal for groups to specify -use flags, although for reasons |
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discussed below this feature should not generally be used. The syntax is |
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the same:</p> |
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<pre class="literal-block"> |
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# This group contains two negative flags |
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GROUP1 flag1 -flag2 -flag3 flag4 |
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</pre> |
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<p>Groups may <em>not</em> contain circular group references. The following example |
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is illegal:</p> |
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<pre class="literal-block"> |
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# Illegal circular references |
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GROUP1 @GROUP2 foo |
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GROUP2 @GROUP1 bar |
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</pre> |
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</div> |
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<div class="section" id="group-descriptions"> |
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<h2><a class="toc-backref" href="#id11" name="group-descriptions">Group Descriptions</a></h2> |
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<p>Groups shall have a textual description associated with them in the same |
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way as USE flags. The file <tt class="literal"><span class="pre">${PORTDIR}/profiles/use.groups.desc</span></tt> |
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contains these:</p> |
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<pre class="literal-block"> |
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# This is a comment |
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DESKTOP Flags which are appropriate for most desktop systems |
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RECOMMENDED Flags which should be enabled on almost all systems |
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</pre> |
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</div> |
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<div class="section" id="using-groups"> |
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<h2><a class="toc-backref" href="#id12" name="using-groups">Using Groups</a></h2> |
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<p>Groups may be used in <tt class="literal"><span class="pre">/etc/make.conf</span></tt>, <tt class="literal"><span class="pre">/etc/portage/package.use</span></tt> and |
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other places where USE flags are normally specified. They may <em>not</em> be |
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used inside <tt class="literal"><span class="pre">IUSE`.</span> <span class="pre">As</span> <span class="pre">before,</span> <span class="pre">the</span> <span class="pre">@</span> <span class="pre">symbol</span> <span class="pre">is</span> <span class="pre">used</span> <span class="pre">to</span> <span class="pre">indicate</span> <span class="pre">that</span> <span class="pre">a</span> |
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<span class="pre">group</span> <span class="pre">is</span> <span class="pre">being</span> <span class="pre">referenced.</span> <span class="pre">For</span> <span class="pre">example,</span> <span class="pre">a</span> <span class="pre">``make.conf</span></tt> for a KDE desktop |
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system might resemble:</p> |
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<pre class="literal-block"> |
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USE="@DESKTOP @KDE perl alsa dvd" |
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</pre> |
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<p>Groups may be preceded by a -sign to invert their contents (that is, all |
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'enable' use flags become -flags, and all -flags become enable flags). Be |
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warned that this feature can cause confusion (see below). Example usage:</p> |
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<pre class="literal-block"> |
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# We have the following groups defined... |
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GROUP1 foo bar |
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GROUP2 -bar baz -fnord |
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GROUP3 @GROUP1 -@GROUP2 -bar foo |
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GROUP4 -foo -bar |
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|
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# And the following... |
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USE="-@GROUP3 @GROUP4 bar" |
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|
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# which resolves to... |
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USE="-@GROUP1 @GROUP2 bar -foo -foo -bar bar" |
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USE="-foo -bar bar -baz fnord bar -foo -foo -bar bar" |
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USE="-baz fnord -foo bar" |
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</pre> |
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</div> |
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<div class="section" id="issues-with-flags-and-groups"> |
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<h2><a class="toc-backref" href="#id13" name="issues-with-flags-and-groups">Issues with -flags and <a class="reference" href="mailto:-@GROUPS">-@GROUPS</a></a></h2> |
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<p>Earlier drafts of this GLEP did not allow -use flags or <a class="reference" href="mailto:-@GROUPS">-@GROUPS</a>. However, |
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because of feedback along the lines of "we shouldn't disallow features |
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just because some users won't understand them" (for example, <a class="footnote-reference" href="#id6" id="id2" name="id2">[3]</a>), these |
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are now allowed but discouraged.</p> |
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<p>The problems are best illustrated by example. Say we have the following |
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groups defined:</p> |
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<pre class="literal-block"> |
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KDE X kde qt |
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GNOME X gtk gtk2 gnome |
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</pre> |
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<p>A user who wants a KDE desktop but no GNOME may do the following:</p> |
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<pre class="literal-block"> |
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USE="@KDE -@GNOME" |
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</pre> |
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<p>However, this will not give the desired effect -- the <tt class="literal"><span class="pre">X</span></tt> USE flag will |
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end up being disabled.</p> |
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<p>Similarly, -use flags could cause a lot of confusion if misused. If, for |
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example, the KDE group turned off GNOME things and the GNOME group turned |
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off KDE things:</p> |
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<pre class="literal-block"> |
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KDE X kde qt -gtk -gnome |
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GNOME X gtk gtk2 gnome -kde -qt |
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</pre> |
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<p>And a user wished to use both KDE and GNOME on a system, and so had USE |
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flags as follows:</p> |
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<pre class="literal-block"> |
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USE="@KDE @GNOME" |
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</pre> |
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<p>They would end up with:</p> |
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<pre class="literal-block"> |
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USE="X kde qt -gtk -gnome X gtk gtk2 gnome -kde -qt" |
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</pre> |
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<p>Which simplifies:</p> |
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<pre class="literal-block"> |
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USE="X gtk gtk2 gnome -kde -qt" |
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</pre> |
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<p>This is clearly not the desired effect.</p> |
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</div> |
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<div class="section" id="adding-new-groups"> |
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<h2><a class="toc-backref" href="#id14" name="adding-new-groups">Adding New Groups</a></h2> |
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<p>The actual groups to be created is beyond the scope of this GLEP, and any |
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group names contained herein should be treated as examples only. Creation |
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of new groups and changing a group's flags should be discussed on the |
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gentoo-dev mailing list as per existing policy for new global USE flags.</p> |
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<p>In particular, any changes involving -flags <em>must</em> be thoroughly discussed |
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before implementation.</p> |
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</div> |
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</div> |
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<div class="section" id="rationale"> |
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<h1><a class="toc-backref" href="#id15" name="rationale">Rationale</a></h1> |
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<p>USE groups will simplify selecting an appropriate set of USE flags for a |
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system.</p> |
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</div> |
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<div class="section" id="reference-implementation"> |
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<h1><a class="toc-backref" href="#id16" name="reference-implementation">Reference Implementation</a></h1> |
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<p>TODO</p> |
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</div> |
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<div class="section" id="backwards-compatibility"> |
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<h1><a class="toc-backref" href="#id17" name="backwards-compatibility">Backwards Compatibility</a></h1> |
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<p>The user will not need to make any changes to keep their current setup. |
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Users who are not running a portage version which supports groups can |
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carry on using current syntax with no side-effects.</p> |
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<p>Some tools which work with make.conf and / or USE flags (for example, |
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<tt class="literal"><span class="pre">ufed</span></tt>) will need to be updated to understand the new group syntax.</p> |
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<p>There is currently a dynamic list of USE flags available on the Gentoo |
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website <a class="footnote-reference" href="#id5" id="id3" name="id3">[2]</a>. For consistency, a similar list will be needed for USE |
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groups.</p> |
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</div> |
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<div class="section" id="references"> |
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<h1><a class="toc-backref" href="#id18" name="references">References</a></h1> |
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<table class="footnote" frame="void" id="id4" rules="none"> |
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<colgroup><col class="label" /><col /></colgroup> |
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<tbody valign="top"> |
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<tr><td class="label"><a class="fn-backref" href="#id1" name="id4">[1]</a></td><td>GLEP 23: Portage handling of ACCEPT_LICENSE |
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(<a class="reference" href="http://www.gentoo.org/proj/en/glep/glep-0023.html">http://www.gentoo.org/proj/en/glep/glep-0023.html</a>)</td></tr> |
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</tbody> |
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</table> |
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<table class="footnote" frame="void" id="id5" rules="none"> |
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<colgroup><col class="label" /><col /></colgroup> |
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<tbody valign="top"> |
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<tr><td class="label"><a class="fn-backref" href="#id3" name="id5">[2]</a></td><td><a class="reference" href="http://www.gentoo.org/dyn/use-index.xml">http://www.gentoo.org/dyn/use-index.xml</a></td></tr> |
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</tbody> |
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</table> |
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<table class="footnote" frame="void" id="id6" rules="none"> |
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<colgroup><col class="label" /><col /></colgroup> |
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<tbody valign="top"> |
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<tr><td class="label"><a class="fn-backref" href="#id2" name="id6">[3]</a></td><td>GLEP 29 discussion on the gentoo-dev mailing list |
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(<a class="reference" href="http://marc.theaimsgroup.com/?l=gentoo-dev&m=109813990013812">http://marc.theaimsgroup.com/?l=gentoo-dev&m=109813990013812</a>)</td></tr> |
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</tbody> |
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</table> |
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</div> |
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<div class="section" id="copyright"> |
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<h1><a class="toc-backref" href="#id19" name="copyright">Copyright</a></h1> |
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<p>This document has been placed in the public domain.</p> |
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<blockquote> |
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vim: set tw=74 :</blockquote> |
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</div> |
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</div> |
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