<p>While running an assert or debug VM, I noticed repeated logs in console:</p>
<blockquote>
<p>(((usqInt)sourceIndex)) < endOfSource 2132</p>
</blockquote>
<p>This corresponds to failing assert: in BitBltSimulation slang</p>
<pre><code>srcLongAt: idx
     <inline: #always>
     self assert: idx asUnsignedInteger < endOfSource.
     ^self long32At: idx
</code></pre>
<p>It is easily reproducible with this Squeak test:</p>
<pre><code>BitmapStreamTests new testShortIntegerArrayReadRefStream2.
</code></pre>
<p>Such read past end is benign, except in rare case when we read past a page boundary and cause a SEGV!</p>
<p>Via LLDB or via VM SImulation, we can find that it is related to the case when we <code>preload </code>a word from source and next source word because we think that we need more than 1 source word to fill 1st dest word.</p>
<p>I have identified and hopefully fixed the bug in VMMaker.oscog-nice.2563<br>
<a href="https://source.squeak.org/VMMaker/VMMaker.oscog-nice.2563.diff" rel="nofollow">https://source.squeak.org/VMMaker/VMMaker.oscog-nice.2563.diff</a></p>

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