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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - FastDemangle performance problem"
href="https://bugs.llvm.org/show_bug.cgi?id=36155">36155</a>
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<th>Summary</th>
<td>FastDemangle performance problem
</td>
</tr>
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<th>Product</th>
<td>lldb
</td>
</tr>
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<th>Version</th>
<td>6.0
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>lldb-dev@lists.llvm.org
</td>
</tr>
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<th>Reporter</th>
<td>feishenniubi@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Here's a simple python program that generates a mangled string with size n:
def gen(n):
prefix = '_Z0'
suffix = 'Mm0'
content = 'M0' * (n-6)
return prefix + content + suffix
lldb's FastDemangler exhibit quadratic behavior when demangling such a string.
On my laptop (2015 Thinkpad t440p Arch Linux), setting n to ~20000 will cause a
noticable slowdown, and ~50000 would just segfault the program.
The same inputs are rejected instantly by itaniumDemangle() as well as c++filt.</pre>
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</p>
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