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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Undetected UB of shift operator with Clang 14"
href="https://bugs.llvm.org/show_bug.cgi?id=52079">52079</a>
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<th>Summary</th>
<td>Undetected UB of shift operator with Clang 14
</td>
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<th>Product</th>
<td>new-bugs
</td>
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<th>Version</th>
<td>12.0
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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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>k.even-mendoza@imperial.ac.uk
</td>
</tr>
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>This code example contains undetected UB with Clang 14 (also older versions):
int main() {
if (0 << 2 % (short)((int)6503265032 << (int)(__CHAR_BIT__ + 6503265032)))
return 0;
return 0;
}
However, if I change a bit the number (e.g., 650326503), then clang-UBSan works
fine; also clang does give a warning during compilation, so UBSan should be
able to detect it.
GCC for example, gives these warnings:
8e588485791c300e738ae2773f5d270b24789c80_copy.c:2:40: runtime error: shift
exponent -2086669552 is negative
8e588485791c300e738ae2773f5d270b24789c80_copy.c:2:14: runtime error: division
by zero</pre>
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