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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 - clang: diagnostics about constexpr misuse are nonexistant"
href="https://bugs.llvm.org/show_bug.cgi?id=37593">37593</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>clang: diagnostics about constexpr misuse are nonexistant
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Frontend
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>lebedev.ri@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre><a href="https://godbolt.org/g/8jgtJU">https://godbolt.org/g/8jgtJU</a>
struct A {
struct B;
static const B c;
template <const B& d>
static void theWork();
};
struct A::B {
int e;
explicit constexpr B(int e_) : e(e_) {}
};
constexpr auto A::c = A::B(0);
template <const A::B& d>
void A::theWork() {
static_assert(d.e == 0, "can't stop the work!");
}
int main(int argc, char* argv[]) {
A::theWork<A::c>();
return 0;
}
clang happily accepts that code.
gcc chokes on it:
<source>:14:19: error: conflicting declaration 'constexpr const auto A::c'
constexpr auto A::c = A::B(0);
^
<source>:3:20: note: previous declaration as 'const A::B A::c'
static const B c;
^
<source>: In instantiation of 'static void A::theWork() [with const A::B& d =
A::c]':
<source>:22:22: required from here
<source>:18:23: error: non-constant condition for static assertion
static_assert(d.e == 0, "can't stop the work!");
~~~~^~~~
<source>:18:23: error: the value of 'A::c' is not usable in a constant
expression
<source>:3:20: note: 'A::c' was not declared 'constexpr'
static const B c;
^
Compiler returned: 1</pre>
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