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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 - non-template friend does not find function template"
href="https://bugs.llvm.org/show_bug.cgi?id=34329">34329</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>non-template friend does not find function template
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>4.0
</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>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>aschepler@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>clang rejects this well-formed code:
template <typename T>
int f(T& obj) { return obj.m; }
class X {
private:
int m;
friend int ::f(X&);
};
int main() {
X x;
f(x);
}
The error message is:
7 : <source>:7:18: error: out-of-line declaration of 'f' does not match any
declaration in the global namespace
friend int ::f(X&);
^
This situation is described in Standard section [temp.friend]. (The wording
was clarified some in C++11, but has the same meaning as in C++03, and has not
changed since.)
Quote:
For a friend function declaration that is not a template declaration:
- if the name of the friend is a qualified or unqualified template-id, the
friend declaration refers to a specialization of a function template,
otherwise,
- if the name of the friend is a qualified-id and a matching non-template
function is found in the specified class or namespace, the friend declaration
refers to that function, otherwise,
- if the name of the friend is a qualified-id and a matching function template
is found in the specified class or namespace, the friend declaration refers to
the deduced specialization of that function template ([]), otherwise,
- the name shall be an unqualified-id that declares (or redeclares) a
non-template function.
End Quote.
In this code, the first bullet does not apply because ::f is not a template-id
(there are no <> tokens). ::f is a qualfied-id, so the second bullet should be
checked, but there is no matching non-template function named ::f. The third
bullet is what makes the code well-formed: the compiler should deduce a
specialization of the function template ::f. Since deduction should succeed,
the friend names a specialization of ::f.
(gcc 7.2, icc 17, and MSVC 19.00.23506 all accept the above code.)</pre>
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