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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - wrong calculation for fold expression in constexpr function"
href="https://bugs.llvm.org/show_bug.cgi?id=47724">47724</a>
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<th>Summary</th>
<td>wrong calculation for fold expression in constexpr function
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>10.0
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++17
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>kirshamir@gmail.com
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<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<p>
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<pre>The following code gets the wrong result if calculated as constexpr (but the
correct result otherwise):
template<bool...Args>
constexpr int reversed_binary_value(){ // ok if removing the constexpr, wrong
otherwise
int res{0},tmp{0};
(tmp|=...|=((res*=2)+=Args));
// std::cout << res << std::endl; // ok with the cout, wrong otherwise
return res;
}
int main()
{
auto val = reversed_binary_value<1,0,1,0>();
assert((val==5)); // ok
assert((reversed_binary_value<1,0,1,0>()==5)); // fails
}
code: <a href="https://godbolt.org/z/Pvq67r">https://godbolt.org/z/Pvq67r</a></pre>
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