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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Clang doesn't warn on some obviously tautological comparisons"
href="https://bugs.llvm.org/show_bug.cgi?id=42666">42666</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Clang doesn't warn on some obviously tautological comparisons
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</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>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>-New Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>chandlerc@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
</td>
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<p>
<div>
<pre><a href="https://godbolt.org/z/iocaCS">https://godbolt.org/z/iocaCS</a>
```
#include <stdlib.h>
enum Flags {
FLAG_A = 0b001,
FLAG_B = 0b010,
FLAG_C = 0b100,
};
void a();
void b();
void c();
void f(Flags f) {
if (!!(f | FLAG_A)) {
a();
} else if (!!(f | FLAG_B)) {
b();
} else if (!!(f | FLAG_C)) {
c();
} else {
abort();
}
}
```
See also: <a href="https://twitter.com/dvyukov/status/1151748350120779781">https://twitter.com/dvyukov/status/1151748350120779781</a></pre>
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