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<title>ProGuard Limitations</title>
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<h2>Limitations</h2>
When using ProGuard, you should be aware of a few technical issues, all of
which are easily avoided or resolved:
<p>
<ul>
<li>For efficiency, ProGuard always ignores any <b>private or package visible
library classes</b> while reading library jars. If any of them are
extended by public library classes, and then extended again by input
classes, ProGuard will complain it can't find them. In that case, you'll
have to use the <code>-dontskipnonpubliclibraryclasses</code> option, and
maybe even the <code>-dontskipnonpubliclibraryclassmembers</code> option.
The graphical user interface has checkboxes for these settings.
<p>
<li>For best results, ProGuard's optimization algorithms assume that the
processed code never <b>intentionally throws NullPointerExceptions</b> or
ArrayIndexOutOfBoundsExceptions, or even OutOfMemoryErrors or
StackOverflowErrors, in order to achieve something useful. For instance,
it may remove a method call <code>myObject.myMethod()</code> if that call
wouldn't have any effect. It ignores the possibility that
<code>myObject</code> might be null, causing a NullPointerException. In
some way this is a good thing: optimized code may throw fewer exceptions.
Should this entire assumption be false, you'll have to switch off
optimization using the <code>-dontoptimize</code> option.
<p>
<li>If an input jar and a library jar contain classes in the <b>same
package</b>, the obfuscated output jar may contain class names that
overlap with class names in the library jar. This is most likely if the
library jar has been obfuscated before, as it will then probably contain
classes named 'a', 'b', etc. Packages should therefore never be split
across input jars and library jars.
<p>
<li>When obfuscating, ProGuard will write out class files named
"<code>a.class</code>", "<code>b.class</code>", etc. If there is a large
numbers of classes in the same package, it may also write out
<b>"<code>aux.class</code>"</b>. Windows doesn't allow creating files with
this reserved name (among a few other names), so it's generally better to
write the output to a jar, in order to avoid such problems.
<p>
</ul>
<p>
<hr>
<address>
Copyright © 2002-2009
<a href="http://www.graphics.cornell.edu/~eric/">Eric Lafortune</a>.
</address>
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