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<body><span class="vcard"><a class="email" href="mailto:richard-llvm@metafoo.co.uk" title="Richard Smith <richard-llvm@metafoo.co.uk>"> <span class="fn">Richard Smith</span></a>
</span> changed
<a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED LATER - Rejects-valid: constexpr and explicit default ctor"
href="http://llvm.org/bugs/show_bug.cgi?id=17694">bug 17694</a>
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<tr>
<th>What</th>
<th>Removed</th>
<th>Added</th>
</tr>
<tr>
<td style="text-align:right;">Status</td>
<td>NEW
</td>
<td>RESOLVED
</td>
</tr>
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<td style="text-align:right;">CC</td>
<td>
</td>
<td>richard-llvm@metafoo.co.uk
</td>
</tr>
<tr>
<td style="text-align:right;">Resolution</td>
<td>---
</td>
<td>LATER
</td>
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<b><a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED LATER - Rejects-valid: constexpr and explicit default ctor"
href="http://llvm.org/bugs/show_bug.cgi?id=17694#c1">Comment # 1</a>
on <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED LATER - Rejects-valid: constexpr and explicit default ctor"
href="http://llvm.org/bugs/show_bug.cgi?id=17694">bug 17694</a>
from <span class="vcard"><a class="email" href="mailto:richard-llvm@metafoo.co.uk" title="Richard Smith <richard-llvm@metafoo.co.uk>"> <span class="fn">Richard Smith</span></a>
</span></b>
<pre>It's helpful to provide the diagnostic when reporting that code is rejected.
Here, Clang says:
<stdin>:9:15: error: default initialization of an object of const type 'const
A' requires a user-provided default constructor
constexpr A a;
^
... which is correct. g++ accepts this because it has speculatively implemented
a resolution to this core issue:
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#253">http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#253</a>
In Clang, we're waiting for the issue to actually be resolved before we take a
direction on it.
Note that 'constexpr' is entirely irrelevant here; the same thing happens with:
class A
{
public:
A() = default;
};
int main(int argc, char** argv)
{
const A a;
}
In either case, g++ also rejects if you add any data member to 'A'.</pre>
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