<html>
<head>
<base href="https://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 --- - erroneous substitution failure through a type alias on variadic template"
href="https://llvm.org/bugs/show_bug.cgi?id=26047">26047</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>erroneous substitution failure through a type alias on variadic template
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>3.6
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</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.s.wallace@intel.com
</td>
</tr>
<tr>
<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=15571" name="attach_15571" title="The test case from the description, but pre-processed">attachment 15571</a> <a href="attachment.cgi?id=15571&action=edit" title="The test case from the description, but pre-processed">[details]</a></span>
The test case from the description, but pre-processed
The following code seems to produce an erroneous substitution failure:
====
template <typename... Ts>
struct function
{
};
template <typename... Ts>
using Callback = function<void(Ts...)>;
template <typename... Ts>
void foo(Callback<Ts...> callback)
{
}
void foo_int(Callback<int> callback)
{
}
template <typename... Ts>
void foo_no_type_indirection(function<void(Ts...)> callback)
{
}
int main()
{
Callback<int> callback = function<void(int)>{};
foo_int(callback); // succeeds
foo_no_type_indirection(callback); // succeeds
foo(callback); // fails: substitution failure
return 0;
}
====
Note that if the substitution is done by hand (the "foo_int" case), the call
succeeds. Also if we don't go through the "Callback" type alias (the
"foo_no_type_indirection" case), the call succeeds. Variadic templates are also
required here; when I tested using a single argument template, clang succeeded.
This test case compiles with gcc4.8.
There are a few other substitution failures kicking around in the bug list, but
none looked quite like this. I thought this test case might be useful even if
it turns out to be a duplicate problem.</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>