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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 INVALID - error: non-type template argument is not a constant expression (GCC compiles, clang doesn't)"
href="https://llvm.org/bugs/show_bug.cgi?id=28711">bug 28711</a>
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<th>What</th>
<th>Removed</th>
<th>Added</th>
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<td style="text-align:right;">Status</td>
<td>NEW
</td>
<td>RESOLVED
</td>
</tr>
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<td style="text-align:right;">CC</td>
<td>
</td>
<td>richard-llvm@metafoo.co.uk
</td>
</tr>
<tr>
<td style="text-align:right;">Resolution</td>
<td>---
</td>
<td>INVALID
</td>
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<b><a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED INVALID - error: non-type template argument is not a constant expression (GCC compiles, clang doesn't)"
href="https://llvm.org/bugs/show_bug.cgi?id=28711#c1">Comment # 1</a>
on <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED INVALID - error: non-type template argument is not a constant expression (GCC compiles, clang doesn't)"
href="https://llvm.org/bugs/show_bug.cgi?id=28711">bug 28711</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>The expression "a.size()", used as a non-type template argument, is not a
constant expression, as Clang reports.
See [expr.const] (5.20)/2.10:
"A conditional-expression e is [not a constant expression if evaluating it]
would evaluate [...]:
2.10) an id-expression that refers to a variable or data member of reference
type unless the reference has a preceding initialization and either
2.10.1) it is initialized with a constant expression or
2.10.2) its lifetime began within the evaluation of e"
The id-expression "a" refers to a variable of reference type that is not
initialized (it's a function parameter) and whose lifetime began outside the
evaluation of e ("a.size()"). We can't determine which object is denoted by
"a", so the expression is non-constant (even though "size()" would not have
looked at that object).</pre>
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