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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - UBSAN fails to catch shifts by more than 1<<32"
href="https://llvm.org/bugs/show_bug.cgi?id=27271">27271</a>
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<th>Summary</th>
<td>UBSAN fails to catch shifts by more than 1<<32
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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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>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>LLVM Codegen
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>cherepan@mccme.ru
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>UBSAN doesn't warn about this program:
int main(int c, char **v) { 1 << ((long)c << 32); }
Run as `clang -Wno-unused-value -fsanitize=undefined example.c && ./a.out`.
Tested with clang version 3.9.0 (trunk 265708) on x86-64.
gcc6 warns:
example.c:1:31: runtime error: shift exponent 4294967296 is too large for
32-bit type 'int'
Looking at IR, it seems the right operand of the shift is checked only after
it's truncated to 32-bit. This is too late.</pre>
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