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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Clang does not use the strictest alignas in templates"
href="https://bugs.llvm.org/show_bug.cgi?id=35028">35028</a>
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<th>Summary</th>
<td>Clang does not use the strictest alignas in templates
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>5.0
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>C++
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>billy.oneal@gmail.com
</td>
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<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>template<class X>
struct alignas(X) alignas(unsigned long) alignas(unsigned int) queue {
unsigned long a;
unsigned int b;
// X suffix[];
};
template struct queue<unsigned short>;
On Godbolt: <a href="https://godbolt.org/g/7MUaSE">https://godbolt.org/g/7MUaSE</a>
2 : <source>:2:8: error: requested alignment is less than minimum alignment of
8 for type 'queue<unsigned short>'
struct alignas(X) alignas(unsigned long) alignas(unsigned int) queue {
^
8 : <source>:8:17: note: in instantiation of template class 'queue<unsigned
short>' requested here
template struct queue<unsigned short>;
^
1 error generated.
Compiler exited with result code
N4687 10.6.2 [dcl.align]/4 says:
The alignment requirement of an entity is the strictest nonzero alignment
specified by its alignment-specifiers, if any; otherwise, the
alignment-specifiers have no effect.
Therefore, even though alignas(X) requests an alignment of 2, less than the
minimum of 8, the following alignas which requests an alignment of 8 should
make the overall alignment request be for 8.</pre>
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