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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - non-type template argument is not a constant expression"
href="https://bugs.llvm.org/show_bug.cgi?id=37863">37863</a>
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<th>Summary</th>
<td>non-type template argument is not a constant expression
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>unspecified
</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
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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++
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>zhonghao@pku.org.cn
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</tr>
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<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>The code is as follow:
template <class T> struct B;
template <bool b>
struct C { };
template <class T>
struct A: C<B<A<T>>::value>
{
typedef T Type;
};
template<class T>
struct B
{
template<typename X> static int check(typename X::Type*);
template<typename> static char check(...);
static const bool value = (sizeof(check<T>(0)) == sizeof(int));
};
int main()
{
return B<A<int>>::value;
}
clang++ rejects the code with error messages:
error: non-type template argument is not a constant expression
struct A: C<B<A<T>>::value>
The code sample comes from a gcc bug report:
<a href="https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62255">https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62255</a>
A previous version of g++ also rejects the code, but it is fixed.
Would you please check whether it indicates a bug in clang++?</pre>
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