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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Alternations in back-references are not handled correctly."
href="https://llvm.org/bugs/show_bug.cgi?id=24879">24879</a>
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<th>Summary</th>
<td>Alternations in back-references are not handled correctly.
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Support Libraries
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>charlesturner7c5@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>I'm trying to match the following code in FileCheck
rev r0, r0
For any ARM register r0. So my check line necessarily looks like this,
CHECK: rev [[R0:r[0-9]+|lr]], [[R0]]
Unfortunately, that fails to match. Letting test contain the above CHECK line,
I get
$ echo "rev r0, r0" | FileCheck test
test:1:8: error: expected string not found in input
CHECK: rev [[R0:r[0-9]+|lr]], [[R0]]
^
<stdin>:1:2: note: scanning from here
rev r0, r0
If test instead contains the line
CHECK: rev [[R0:r[0-9]+]], [[R0]]
It does match rev r0, r0. The alternation is the problem. I had a quick look at
the code and found that the above CHECK line essentially expands to this,
$ echo "rev lr, lr" | egrep '(r[0-9]+|lr), \1'
That egrep command *does* match, so indeed, there must be a bug in the
implementation in Regex.cpp, which appears to call out to something from
OpenBSD's libc/regex implementation.
I didn't get time to dig into that code. I also couldn't find any easily
searchable OpenBSD bug tracker in the 30 seconds I spent looking.</pre>
</div>
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