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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - constexpr variable initialisation error after forwarding reference"
href="https://bugs.llvm.org/show_bug.cgi?id=43086">43086</a>
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<th>Summary</th>
<td>constexpr variable initialisation error after forwarding reference
</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>PC
</td>
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<th>OS</th>
<td>Linux
</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
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<th>Reporter</th>
<td>pkeir@outlook.com
</td>
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<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=22413" name="attach_22413" title="Code as described.">attachment 22413</a> <a href="attachment.cgi?id=22413&action=edit" title="Code as described.">[details]</a></span>
Code as described.
The C++11 code below (also attached) will fail to compile:
struct Bar {};
struct Foo { Bar t; };
template <typename T>
constexpr T jam(T &&a) { return a; }
void test()
{
Foo y;
constexpr Foo x = jam(y);
}
Changing the types of x and y from Foo to Bar will remove the error. GCC
snapshot 17th August 2019 produces no error. The error message follows:
constexpr_rvalue.cpp:10:17: error: constexpr variable 'x' must be initialized
by a constant expression
constexpr Foo x = jam(y);
^ ~~~~~~
constexpr_rvalue.cpp:10:21: note: read of non-constexpr variable 'y' is not
allowed in a constant expression
constexpr Foo x = jam(y);
^
constexpr_rvalue.cpp:10:21: note: in call to 'Foo(y)'
constexpr_rvalue.cpp:9:7: note: declared here
Foo y;
^
1 error generated.</pre>
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