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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - non-constexpr recursive variable templates are instanciated wrongly"
href="https://llvm.org/bugs/show_bug.cgi?id=29033">29033</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>non-constexpr recursive variable templates are instanciated wrongly
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>3.8
</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>
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<th>Component</th>
<td>C++14
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>felix.morgner@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=16980" name="attach_16980" title="Code generated by clang++ -std=c++14 -Wall -Wextra -pedantic -S">attachment 16980</a> <a href="attachment.cgi?id=16980&action=edit" title="Code generated by clang++ -std=c++14 -Wall -Wextra -pedantic -S">[details]</a></span>
Code generated by clang++ -std=c++14 -Wall -Wextra -pedantic -S
The following code:
#include <iostream>
template<std::size_t N>
auto fibo_v{fibo_v<N-1> + fibo_v<N-2>};
template<>
auto fibo_v<0>{0};
template<>
auto fibo_v<1>{1};
int main()
{
std::cout << fibo_v<4> << '\n';
}
produces 0 as its output. Adding constexpr to the variable declarations
resolves this and produces the correct result 3.
As far as i can tell, N3651 lifted the restriction on variable templates to be
constexpr, thus i would expect the same result with and without constexpr in
the declarations.
GCC 6.1.1 produces the correct output, regardless of constexpr being in place
or not.</pre>
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