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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - out of range iterator usage in getLongestCommonPrefixLen (r280895)"
href="https://llvm.org/bugs/show_bug.cgi?id=30515">30515</a>
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<th>Summary</th>
<td>out of range iterator usage in getLongestCommonPrefixLen (r280895)
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<th>Product</th>
<td>new-bugs
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>new bugs
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>yaron.keren@gmail.com
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</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, vsk@apple.com
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>getLongestCommonPrefixLen calls the three-argument version of std::mismatch:
std::mismatch(Strings[0].begin(), Strings[0].end(), Strings[I].begin())
with this call, Strings[I].end() is *assumed* to be Strings[I].begin() +
Strings[0].end() - Strings[0].begin(), see:
<a href="http://en.cppreference.com/w/cpp/algorithm/mismatch">http://en.cppreference.com/w/cpp/algorithm/mismatch</a>
If last2 is not provided (overloads (1-4)), it denotes first2 + (last1 -
first1).
in case String[I] is a prefix of Strings[0], std::mismatch will continue
increasing its iterator outside String[I]. This is caught by Visual C++ runtime
lib in debug mode, "string iterator + offset out of range". the code probably
works since the strings are null-terminated but at least VC thinks it is wrong.
the four-argument std::mismatch could solve this but sadly is C++ 17.
maybe it's best just to hardcode the while loop.</pre>
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