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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<!--
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Copyright 2006 Sun Microsystems, Inc. All Rights Reserved.
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DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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This code is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License version 2 only, as
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published by the Free Software Foundation. Sun designates this
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particular file as subject to the "Classpath" exception as provided
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by Sun in the LICENSE file that accompanied this code.
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This code is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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version 2 for more details (a copy is included in the LICENSE file that
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accompanied this code).
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You should have received a copy of the GNU General Public License version
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2 along with this work; if not, write to the Free Software Foundation,
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Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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CA 95054 USA or visit www.sun.com if you need additional information or
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have any questions.
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-->
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<html>
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<head>
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<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
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<meta name="author" content="Jonathan Gibbons">
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<link type="text/css" rel=stylesheet href="style.css">
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<title>JavaCompiler's "to do" list</title>
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</head>
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<body>
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<h3>com.sun.tools.javac.main.JavaCompiler's "to do" list</h3>
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<p>
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After the source files have been parsed, and their symbols entered
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in the symbol table, the top level classes and some other items end
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up on JavaCompiler's "to do" list.
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</p>
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<p>
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For each entry on the "to do" list, <code>JavaCompiler</code>
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processes it as follows:
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</p>
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<ul>
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<li><p>Some parts of the compilation involve modifying the parse tree,
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so a copy of the root of the tree is kept prior to such manipulation.
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</p>
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<p class="note">
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Note: this copy is just used to check whether the class is one of those
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found in a compilation unit on the command line (i.e. in rootClasses).
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</p>
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<li><p>The top level classes are "attributed", using
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<a href="../../src/share/classes/com/sun/tools/javac/comp/Attr.java" class="code">Attr</a>,
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meaning that names and other elements within the parse tree are resolved
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and associated with the corresponding types and symbols. Many semantic
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errors may be detected here, either by <code>Attr</code>, or by
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<a href="../../src/share/classes/com/sun/tools/javac/comp/Check.java" class="code">Check</a>.
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</p>
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<p>While attributing the tree, class files will be read as necessary.
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In addition, if a class is required, and a source file for the class is found
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that is newer than the class file, the source file will be automatically parsed
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and put on the "to do" list. This is done by registering JavaCompiler as an
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implementation of
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<a href="../../src/share/classes/com/sun/tools/javac/comp/Attr.java" class="code">Attr</a><span class=code>.SourceCompleter</span>.
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</p>
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<p class=note>
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Note: there is a hidden option <code>-attrparseonly</code> which can be used to skip
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the rest of the processing for this file. In so doing, it "breaks" the
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protocol use to save and restore the source file used to report error
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messages (Log.useSource). There is a "try finally" block which
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could reasonably be used/extended to restore the source file correctly.
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</p>
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</li>
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<li><p>If there are no errors so far, flow analysis will be done for the class, using
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<a href="../../src/share/classes/com/sun/tools/javac/comp/Flow.java" class="code">Flow</a>.
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Flow analysis is used to check for definite assignment to variables,
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and unreachable statements, which may result in additional errors.
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</p>
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<p class="note">Note: flow analysis can be suppressed with the hidden
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option <code>-relax</code>.
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</p>
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</li>
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<li>If the "to do" item is a TopLevel tree, it will be the contents of a
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<span class="code">package-info.java</span> file, containing annotations for a package.
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(See notes for <a href="Enter.html#package-info">Enter</a>.)
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<ul>
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<li>Syntactic sugar is processed, using
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<a href="../../src/share/classes/com/sun/tools/javac/comp/Lower.java" class="code">Lower</a>.
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<code>Lower</code> is defined to return a list of trees for the translated classes
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and all the translated inner classes.</li>
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<li>If <code>Lower</code> returns a non-empty list, there is an assertion that
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the list has a single element, in which case, code is generated, using
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<a href="../../src/share/classes/com/sun/tools/javac/jvm/Gen.java" class="code">Gen</a>,
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and the resulting code is written out using
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<a href="../../src/share/classes/com/sun/tools/javac/jvm/ClassWriter.java" class="code">ClassWriter</a>.
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</li>
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<li>No further processing is done on this "to do" item.<br>
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</li>
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</ul>
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<p class=note>Note that <a href="Enter.html">Enter</a> will have processed all other TopLevel
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putting the individual classes that it finds there on the "to do"
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(and not the TopLevel node itself.)
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</p>
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<li>If stub outputs have been requested, with the hidden <code>-stubs</code> option,
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<ul>
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<li>If the class was one of those mentioned on the command line and is in
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<span class=code>java.lang</span>,
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pretty print the source with no method bodies.</li>
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<li>No further processing is done on this "to do" item. </li>
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</ul>
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<li>Code involving generic types is translated to code without generic types, using
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<a href="../../src/share/classes/com/sun/tools/javac/comp/TransTypes.java" class="code">TransTypes</a>.
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</li>
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<li>If source output has been requested, with the hidden <code>-s</code> option
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<ul>
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<li>If the original tree was from command line, pretty print the source code
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</li>
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<li>No further processing is done on this "to do" item.</li>
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</ul>
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<li>Syntactic sugar is processed, using
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<a href="../../src/share/classes/com/sun/tools/javac/comp/Lower.java" class="code">Lower</a>.
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This takes care of inner classes, class literals, assertions, foreach
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loops, etc.
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<code>Lower</code> is defined to return a list of trees for the translated classes
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and all the translated inner classes.</li>
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<p class=note>
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Note: see also the use of <code>Lower</code> earlier in the loop, when processing
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TopLevel trees.</p>
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<li>For each class returned by <code>Lower</code><br>
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<ul>
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<li>If source has been requestion with the hidden <code>-printflat</code>
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option, the source of the class is printed.
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<li>Otherwise, code for the class is generated, using
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<a href="../../src/share/classes/com/sun/tools/javac/jvm/Gen.java" class="code">Gen</a>,
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and the resulting code is written out using
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<a href="../../src/share/classes/com/sun/tools/javac/jvm/ClassWriter.java" class="code">ClassWriter</a>.
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</ul>
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</ul>
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<h4>Issues</h4>
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The "to do" list is mostly organized by top level classes, and not by
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compilation units. This means that if a compilation unit contains several
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classes, it is possible for code to be generated for some of the classes
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in the file, at which point at error may be detected for one of the
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remaining classes, preventing code from being generated for that and any
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subsequent classes. This means that the compilation unit will be partially
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compiled, with some but not all of the class files being generated.
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(Bug <a href="http://monaco.sfbay.sun.com/detail.jsf?cr=5011101">5011101</a>)
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</body>
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</html>
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