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<body><span class="vcard"><a class="email" href="mailto:richard-llvm@metafoo.co.uk" title="Richard Smith <richard-llvm@metafoo.co.uk>"> <span class="fn">Richard Smith</span></a>
</span> changed
<a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED MOVED - Unsafe perfect forwarding"
href="http://llvm.org/bugs/show_bug.cgi?id=20174">bug 20174</a>
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<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>What</th>
<th>Removed</th>
<th>Added</th>
</tr>
<tr>
<td style="text-align:right;">Status</td>
<td>REOPENED
</td>
<td>RESOLVED
</td>
</tr>
<tr>
<td style="text-align:right;">Resolution</td>
<td>---
</td>
<td>MOVED
</td>
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<b><a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED MOVED - Unsafe perfect forwarding"
href="http://llvm.org/bugs/show_bug.cgi?id=20174#c5">Comment # 5</a>
on <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED MOVED - Unsafe perfect forwarding"
href="http://llvm.org/bugs/show_bug.cgi?id=20174">bug 20174</a>
from <span class="vcard"><a class="email" href="mailto:richard-llvm@metafoo.co.uk" title="Richard Smith <richard-llvm@metafoo.co.uk>"> <span class="fn">Richard Smith</span></a>
</span></b>
<pre>(In reply to <a href="show_bug.cgi?id=20174#c4">comment #4</a>)
<span class="quote">> > 7 Requires: sizeof...(Types) == sizeof...(UTypes).
> > is_constructible<Ti, Ui&&>::value is true for all i.</span >
Since this was violated, 17.6.4.11/1 applies:
"Violation of the preconditions specified in a function’s Requires: paragraph
results in undefined behavior unless the function’s Throws: paragraph specifies
throwing an exception when the precondition is violated."
... so we're permitted (and, as far as I can tell, required) to accept this
tuple construction, and libc++'s extension is a conforming one.
If you think that this tuple constructor should not participate in overload
resolution if it has an arity mismatch, please file a defect report against the
C++ standard library. Mail <a href="mailto:lwgchair@gmail.com">lwgchair@gmail.com</a> for that. (Resolving 'MOVED'.)</pre>
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