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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 - Inconsitency between variable decltype(auto) in variables and templates"
href="https://bugs.llvm.org/show_bug.cgi?id=47792">47792</a>
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<th>Summary</th>
<td>Inconsitency between variable decltype(auto) in variables and templates
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>All
</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>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>C++17
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>anders.granlund.0@gmail.com
</td>
</tr>
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<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>Consider the following program:
#include <iostream>
#include <type_traits>
template<decltype(auto) N>
void f()
{
std::cout << std::is_same_v<decltype(N), int> << std::endl;
}
int main()
{
const int i = 0;
f<i>();
decltype(auto) N = i;
std::cout << std::is_same_v<decltype(N), const int> << std::endl;
}
When compiling it with -std=c++17 -pedantic-errors and the running it the
following is outputed:
1
1
This means that the two decltype(auto) deductions behaved differently since
they deduced different types ( N = int and N = const int ). I expect them to
behave the same way.
Note that gcc gives the expected result ( N = const int for both deductions ).
Link to compiler explorer (clang to the left, gcc to the right):
<a href="https://godbolt.org/z/Y5Yc7M">https://godbolt.org/z/Y5Yc7M</a></pre>
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