<html>
<head>
<base href="https://llvm.org/bugs/" />
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - member function of template instantiated even though only declaration is needed"
href="https://llvm.org/bugs/show_bug.cgi?id=27221">27221</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>member function of template instantiated even though only declaration is needed
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>C++11
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>rbock@eudoxos.de
</td>
</tr>
<tr>
<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>This code fails to compile:
template<typename T>
struct X
{
X(X&&) { static_assert(sizeof(T) < 1, "Intentional Failure"); }
};
auto impl() -> X<int>;
auto test() -> decltype(impl())
{
return impl();
}
int main()
{
test();
}
My understanding is that it should compile just fine. I admit, I started a
discussion on stackoverflow for this (see
<a href="http://stackoverflow.com/questions/36371571/clang-and-gcc-vs-msvc-and-icc-is-a-static-assert-in-the-copy-move-constructor-r">http://stackoverflow.com/questions/36371571/clang-and-gcc-vs-msvc-and-icc-is-a-static-assert-in-the-copy-move-constructor-r</a>)
Citing from the answer I deem correct:
Copy elision requires declaration of copy/move constructors but doesn't require
definition.
Member function definitions of templates are not instantiated unless their
definitions are required.
If a definition is not instantiated it cannot be tested for being ill-formed.
References:
14.7.1.1 …The implicit instantiation of a class template specialization causes
the implicit instantiation of the declarations, but not of the definitions,
default arguments, or exception-specifications of the class member functions…
14.7.1.2 Unless a member of a class template… has been explicitly instantiated
or explicitly specialized, the specialization of the member is implicitly
instantiated when the specialization is referenced in a context that requires
the member definition to exist…</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>