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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - UBSan goes off on uniform_int_distribution"
href="https://bugs.llvm.org/show_bug.cgi?id=34663">34663</a>
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<th>Summary</th>
<td>UBSan goes off on uniform_int_distribution
</td>
</tr>
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<th>Product</th>
<td>libc++
</td>
</tr>
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<th>Version</th>
<td>5.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>All
</td>
</tr>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>All Bugs
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>mclow.lists@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
</tr></table>
<p>
<div>
<pre>ON x86_64 Linux, UBSan complains when the following program is run:
#include <array>
#include <random>
#include <cassert>
uint32_t array[1024 * 1024];
int main () {
std::mt19937 randEngine;
std::uniform_int_distribution<uint32_t> dist;
for (auto &i : array)
i = dist(randEngine);
std::sort(std::begin(array), std::end(array));
assert(std::is_sorted(std::begin(array), std::end(array)));
}
in particular, it doesn't like the line <algorithm>:3025.
This does no occur on Mac OS. BUT, if you change the `randEngine` declaration
to
std::mersenne_twister_engine<unsigned long, 32ul, 624ul, 397ul, 31ul,
2567483615ul, 11ul, 4294967295ul, 7ul, 2636928640ul, 15ul, 4022730752ul, 18ul,
1812433253ul> randEngine;
then UBSan will fire on Mac OS as well.</pre>
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