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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Problem with in-class frient function template"
href="http://llvm.org/bugs/show_bug.cgi?id=20433">20433</a>
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<th>Summary</th>
<td>Problem with in-class frient function template
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>-New Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>jpr@polytech.unice.fr
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The following (minimalized) program fails to compile with clang++ 3.4 (release)
and clang 3.5.0 (trunk 213845) (llvm/trunk 213844):
struct A {
template <typename U>
friend U f(const A& a) {return U{};}
};
int main() {
A a;
double x = f<double>(a);
}
Here is the corresponding error message:
clang++ -std=c++11 -Wall infriend.cpp
infriend.cpp:8:16: error: use of undeclared identifier 'f'
double x = f<double>(A{});
^
infriend.cpp:8:24: error: expected '(' for function-style cast or type
construction
double x = f<double>(A{});
~~~~~~^
The program compiles if I define the body of function f() outside the class:
struct A {
template <typename U>
friend U f(const A& a);
};
template <typename U>
inline U f(const A& a) {return U{};}
int main() {
A a;
double x = f<double>(a);
}
However, this solution is impossible if struct A is itself a template. We
**have to** define it within the class, don't we?
template <typename T>
struct A {
template <typename U>
friend U f(const A& a) {return U{};}
};
int main() {
A<int> a;
double x = f<double>(a);
}
and compilation fails with the same message as above.
Note that gcc-4.8.x/4.9.x compiles correctly these examples.</pre>
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