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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Error with consteval constructor in unevaluated sizeof context, claims constructor is undefined"
href="https://bugs.llvm.org/show_bug.cgi?id=47385">47385</a>
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<th>Summary</th>
<td>Error with consteval constructor in unevaluated sizeof context, claims constructor is undefined
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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>enhancement
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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>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>stephan.bergmann.secondary@googlemail.com
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<pre>With recent Clang 12 trunk, but not with e.g. clang-10.0.0-2.fc32.x86_64:
<span class="quote">> $ cat test.cc
> template<typename> struct S { consteval S() {} };
> int f(S<void> const &);
> int g() { return sizeof (f(S<void>())); }</span >
<span class="quote">> $ clang++ -std=c++20 -fsyntax-only test.cc
> test.cc:3:28: error: call to consteval function 'S<void>::S' is not a constant expression
> int g() { return sizeof (f(S<void>())); }
> ^
> test.cc:3:28: note: undefined constructor 'S' cannot be used in a constant expression
> test.cc:1:41: note: declared here
> template<typename> struct S { consteval S() {} };
> ^
> 1 error generated.</span >
(Issue 47350 looks similar, but no idea whether they have the same root cause.)</pre>
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