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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - C++2a std::midpoint's "Constraints" are not implemented"
href="https://bugs.llvm.org/show_bug.cgi?id=42037">42037</a>
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</tr>
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<th>Summary</th>
<td>C++2a std::midpoint's "Constraints" are not implemented
</td>
</tr>
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<th>Product</th>
<td>libc++
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>All Bugs
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>arthur.j.odwyer@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
</tr></table>
<p>
<div>
<pre>// <a href="https://godbolt.org/z/mAL4Sd">https://godbolt.org/z/mAL4Sd</a>
#include <numeric>
int a();
int b();
int main() {
std::midpoint(a, b);
}
====
/c++/v1/numeric:554:52: error: arithmetic on pointers to the function type 'int
()'
return __a + _VSTD::midpoint(ptrdiff_t(0), __b - __a);
~~~ ^ ~~~
According to N4810, std::midpoint for `T*` should be constrained to require `T`
to be a complete object type (not a function type, and not cv void either).
I'm fairly confident that no library code should ever try to constrain on
`is_pointer` without also asking whether it's an object pointer, function
pointer, member pointer, or void pointer. It might be worth auditing the entire
libc++ codebase for uses of `is_pointer`.</pre>
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</p>
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