<html>
<head>
<base href="http://llvm.org/bugs/" />
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Mysterious error with inheriting constructor, delegating constructor, and noexcept specifier"
href="http://llvm.org/bugs/show_bug.cgi?id=15757">15757</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Mysterious error with inheriting constructor, delegating constructor, and noexcept specifier
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Windows NT
</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>
<tr>
<th>Component</th>
<td>C++11
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>eric@boostpro.com
</td>
</tr>
<tr>
<th>CC</th>
<td>dgregor@apple.com, llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>This is as far as I've been able to narrow this problem down. It seems to be
some strange confluence of C++11 features that is causing the perfect storm:
{{{
struct S
{};
template<typename X, typename Y>
struct T
{
template<typename A>
T(X x, A &&a)
{}
template<typename A>
explicit T(A &&a)
noexcept(noexcept(
T(X(), static_cast<A &&>(a))
))
: T(X(), static_cast<A &&>(a))
{}
};
template<typename X, typename Y>
struct U
: T<X, Y>
{
using T<X, Y>::T;
};
// Comment this function out and everything works
U<S, char> foo(char ch)
{
return U<S, char>(ch);
}
int main()
{
U<S, int> a(42); // This works
U<S, char> b('4'); // This fails
}
}}}
The error I'm getting is:
1> "C:/cygwin/usr/local/bin/clang++.exe" -c -O0 -std=gnu++11 main.cpp -o
main.o
1> main.cpp:14:20: error: cannot cast from lvalue of type 'char' to rvalue
reference type 'S &&'; types are not compatible
1> T(X(), static_cast<A &&>(a))
1> ^~~~~~~~~~~~~~~~~~~~
1> main.cpp:24:20: note: in instantiation of exception specification for
'T<char>' requested here
1> using T<X, Y>::T;
1> ^
1> main.cpp:36:16: note: inheriting constructor for 'U<S, char>' first
required here
1> U<S, char> b('4'); // This fails
1> ^
1> 1 error generated.
I can't make any sense of the error message. Seemingly innocuous changes to the
code, like commenting out the foo function or the noexcept clause, make the
error go away.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>