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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Result of left-shifting an unsigned char is (promoted to?) signed."
href="https://bugs.llvm.org/show_bug.cgi?id=52234">52234</a>
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<th>Summary</th>
<td>Result of left-shifting an unsigned char is (promoted to?) signed.
</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>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>new bugs
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>andrew@aitchison.me.uk
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=25378" name="attach_25378" title="c++ source that exhibits the problem">attachment 25378</a> <a href="attachment.cgi?id=25378&action=edit" title="c++ source that exhibits the problem">[details]</a></span>
c++ source that exhibits the problem
Compile the attached source
signed_shifts.cpp
with
clang++ -Wsign-conversion -Werror -c -o signed_shifts.o signed_shifts.cpp
With clang++9, clang++-11, clang++-12 or clang++-13, as supplied by Ubuntu
21.10
I get
error: implicit conversion changes signedness: 'int' to 'unsigned int'
[-Werror,-Wsign-conversion]
when an unsigned char is left-shifted and stored in an unsigned int,
unless the result is explicitly cast back to unsigned.
I also see this with gnu g++4,5,6,7,8,9 (9.4.0-3ubuntu1)
but not g++-10 (10.3.0-11ubuntu1 or g++-11 11.2.0-7ubuntu2.</pre>
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