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7<title>ProGuard Limitations</title>
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11<h2>Limitations</h2>
12
13When using ProGuard, you should be aware of a few technical issues, all of
14which are easily avoided or resolved:
15<p>
16<ul>
17
18<li>For efficiency, ProGuard always ignores any <b>private or package visible
19    library classes</b> while reading library jars. If any of them are
20    extended by public library classes, and then extended again by input
21    classes, ProGuard will complain it can't find them. In that case, you'll
22    have to use the <code>-dontskipnonpubliclibraryclasses</code> option, and
23    maybe even the <code>-dontskipnonpubliclibraryclassmembers</code> option.
24    The graphical user interface has checkboxes for these settings.
25    <p>
26
27<li>For best results, ProGuard's optimization algorithms assume that the
28    processed code never <b>intentionally throws NullPointerExceptions</b> or
29    ArrayIndexOutOfBoundsExceptions, or even OutOfMemoryErrors or
30    StackOverflowErrors, in order to achieve something useful. For instance,
31    it may remove a method call <code>myObject.myMethod()</code> if that call
32    wouldn't have any effect. It ignores the possibility that
33    <code>myObject</code> might be null, causing a NullPointerException. In
34    some way this is a good thing: optimized code may throw fewer exceptions.
35    Should this entire assumption be false, you'll have to switch off
36    optimization using the <code>-dontoptimize</code> option.
37    <p>
38
39<li>If an input jar and a library jar contain classes in the <b>same
40    package</b>, the obfuscated output jar may contain class names that
41    overlap with class names in the library jar. This is most likely if the
42    library jar has been obfuscated before, as it will then probably contain
43    classes named 'a', 'b', etc. Packages should therefore never be split
44    across input jars and library jars.
45    <p>
46
47<li>When obfuscating, ProGuard will write out class files named
48    "<code>a.class</code>", "<code>b.class</code>", etc. If there is a large
49    numbers of classes in the same package, it may also write out
50    <b>"<code>aux.class</code>"</b>. Windows doesn't allow creating files with
51    this reserved name (among a few other names), so it's generally better to
52    write the output to a jar, in order to avoid such problems.
53    <p>
54
55</ul>
56<p>
57
58<hr>
59<address>
60Copyright &copy; 2002-2009
61<a href="http://www.graphics.cornell.edu/~eric/">Eric Lafortune</a>.
62</address>
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