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7<title>ProGuard Limitations</title>
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24<h2>Limitations</h2>
25
26When using ProGuard, you should be aware of a few technical issues, all of
27which are easily avoided or resolved:
28<p>
29<ul class="spacious">
30
31<li>For best results, ProGuard's optimization algorithms assume that the
32    processed code never <b>intentionally throws NullPointerExceptions</b> or
33    ArrayIndexOutOfBoundsExceptions, or even OutOfMemoryErrors or
34    StackOverflowErrors, in order to achieve something useful. For instance,
35    it may remove a method call <code>myObject.myMethod()</code> if that call
36    wouldn't have any effect. It ignores the possibility that
37    <code>myObject</code> might be null, causing a NullPointerException. In
38    some way this is a good thing: optimized code may throw fewer exceptions.
39    Should this entire assumption be false, you'll have to switch off
40    optimization using the <code>-dontoptimize</code> option.</li>
41
42<li>ProGuard's optimization algorithms currently also assume that the
43    processed code never creates <b>busy-waiting loops</b> without at least
44    testing on a volatile field. Again, it may remove such loops. Should this
45    assumption be false, you'll have to switch off optimization using
46    the <code>-dontoptimize</code> option.</li>
47
48<li>If an input jar and a library jar contain classes in the <b>same
49    package</b>, the obfuscated output jar may contain class names that
50    overlap with class names in the library jar. This is most likely if the
51    library jar has been obfuscated before, as it will then probably contain
52    classes named 'a', 'b', etc. Packages should therefore never be split
53    across input jars and library jars.</li>
54
55<li>When obfuscating, ProGuard writes out class files named
56    "<code>a.class</code>", "<code>b.class</code>", etc. If a package contains
57    a large number of classes, ProGuard may also write out
58    <b>"<code>aux.class</code>"</b>. Inconveniently, Windows refuses to create
59    files with this reserved name (among a few other names). It's generally
60    better to write the output to a jar, in order to avoid such problems.</li>
61
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65<address>
66Copyright &copy; 2002-2014
67<a target="other" href="http://www.lafortune.eu/">Eric Lafortune</a> @ <a target="top" href="http://www.saikoa.com/">Saikoa</a>.
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