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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - __builtin_constant_p returns 1 instead of 0 when there is a side effect"
href="https://bugs.llvm.org/show_bug.cgi?id=43557">43557</a>
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<th>Summary</th>
<td>__builtin_constant_p returns 1 instead of 0 when there is a side effect
</td>
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<th>Product</th>
<td>new-bugs
</td>
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<th>Version</th>
<td>9.0
</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>
</tr>
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<th>Severity</th>
<td>release blocker
</td>
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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
</td>
</tr>
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<th>Reporter</th>
<td>vincent-llvm@vinc17.net
</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>If the value of __builtin_constant_p is constant, 1 is returned even when there
is a side effect. This is a regression in Clang 9.
Testcase:
#include <stdio.h>
int main (void)
{
int c, i = 0;
c = __builtin_constant_p ((i++, 0));
printf ("%d %d\n", c, i);
return 0;
}
which outputs "1 0" instead of "0 0" with:
clang version 9.0.0-1 (tags/RELEASE_900/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
(Debian package clang-9 1:9-1).
Note: This makes one test of GNU MPFR fail (tcmp_ui) and can affect code using
MPFR, when this user code is built with Clang 9.</pre>
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