<html>
    <head>
      <base href="https://llvm.org/bugs/" />
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - __cxa_demangle consumes 6.5Gb on "___Z2i_D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D""
   href="https://llvm.org/bugs/show_bug.cgi?id=31031">31031</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>__cxa_demangle consumes 6.5Gb on "___Z2i_D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D"
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>new-bugs
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>unspecified
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>new bugs
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>kcc@google.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Feed "___Z2i_D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D"
into __cxa_demangle and watch it consume 6.5 Gb of RAM:

#include <stddef.h>
extern "C" char *
__cxa_demangle(const char *mangled_name, char *buf, size_t *n, int *status);


int main() {
 
__cxa_demangle("___Z2i_D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D1D",
0, 0, 0);
}

clang++ -std=c++11 -g   cxa_demangle.cpp -I../include repro.cc -o repro

/usr/bin/time ./repro 
8.55user 2.41system 0:10.98elapsed 99%CPU (0avgtext+0avgdata
6557996maxresident)k


(found by libFuzzer, see also
<a href="https://bugs.chromium.org/p/chromium/issues/detail?id=606626">https://bugs.chromium.org/p/chromium/issues/detail?id=606626</a>)</pre>
        </div>
      </p>
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