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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Clang in C++11 mode refuses to get address of templated function as template parameter"
href="http://llvm.org/bugs/show_bug.cgi?id=17030">17030</a>
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<th>Summary</th>
<td>Clang in C++11 mode refuses to get address of templated function as template parameter
</td>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>3.1
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>C++11
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
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<th>Reporter</th>
<td>felixcca@yahoo.ca
</td>
</tr>
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<th>CC</th>
<td>dgregor@apple.com, llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Apple's Clang that ships with Xcode 4.6.3 fails to parse the following program:
template<void (*F)(void)>
struct Func {};
template<typename T>
void foo();
int main() {
struct Bar {}; // function-local type
Func<foo<Bar>> x;
}
The error is the following, on the line that declares `x` in `main`:
<span class="quote">> error: non-template argument refers to function 'foo<Bar>' with internal linkage
> Func<foo<Bar>> x;
> ^~~~~~~~</span >
I might be mistaken as I'm not very familiar with linkage, but this seems to
run afoul of n3242's ยง14.3.2:
<span class="quote">> A template-argument for a non-type, non-template template-parameter shall be one of:
> [...]
> - a constant expression (5.19) that designates the address of an object with static storage duration and external or internal linkage or __a function with external or internal linkage__, including function templates and function template-ids but excluding non-static class members [...]</span >
It also happens (according to this guy: <a href="http://stackoverflow.com/q/18498957/">http://stackoverflow.com/q/18498957/</a>)
with Clang 3.4 (trunk 187493), although in this case it says the function "has
no linkage" (which seems to be a better reason to refuse it).
G++ will gladly compile that code.
It should also be noted that this works with clang:
template<typename T>
void foo();
int main() {
struct Bar {}; // function-local type
void (*y)() = foo<Bar>;
}</pre>
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