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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Bug: undefined behavior of constexpr static_cast from int to unscoped enum without fixed type outside range compiles fine on C++17"
href="https://bugs.llvm.org/show_bug.cgi?id=50711">50711</a>
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<th>Summary</th>
<td>Bug: undefined behavior of constexpr static_cast from int to unscoped enum without fixed type outside range compiles fine on C++17
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
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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>carlosgalvezp@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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<pre>Hi,
The following code is undefined behavior in C++17. And undefined behavior is
not allowed in constant expressions - the compiler is required to diagnose it.
Adapted from cppreference:
enum foo { a = 0, b = 1 };
constexpr foo x = static_cast<foo>(123); // undefined behavior since C++17
However Clang happily compiles this code:
<a href="https://godbolt.org/z/bzhWMxqoE">https://godbolt.org/z/bzhWMxqoE</a></pre>
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