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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - max_align_t expected by libc++, but missing in Visual Studio 2019's CRT"
href="https://bugs.llvm.org/show_bug.cgi?id=49116">49116</a>
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<th>Summary</th>
<td>max_align_t expected by libc++, but missing in Visual Studio 2019's CRT
</td>
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<th>Product</th>
<td>libc++
</td>
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<th>Version</th>
<td>11.0
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
</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>All Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>colin@reactos.org
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
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<p>
<div>
<pre>I have built libc++ 11.0.1 using Visual Studio 2019's clang-cl 10.0.0 against
the Microsoft CRT (version 14.28.29333).
When compiling any application that includes libc++'s <cstddef>, I get a build
failure:
cstddef(53,9): error : no member named 'max_align_t' in the global namespace
While it's correct that <cstddef> needs to provide std::max_align_t since
C++11, the corresponding max_align_t that libc++ expects in the global
namespace also requires C11 support.
However, Visual Studio and its CRT lack full C11 support.
Visual Studio's STL works around this by defining std::max_align_t to double in
its <cstddef> instead of importing it from the global namespace.
Visual Studio's <stddef.h> lacks any mentioning of max_align_t.
For the moment, I can work around this by adding 'using max_align_t = double;'
to libc++'s <cstddef>. Considering that Clang is now officially supported by
Visual Studio, this needs a proper fix though.
Alternatively, you can officially declare that C++11 support requires C11
support and leave it to Microsoft to add the missing C11 support to Visual
Studio ;)
Note that this is no duplicate of <a class="bz_bug_link
bz_status_NEW "
title="NEW - error: no member named 'max_align_t' in the global namespace"
href="show_bug.cgi?id=20196">bug #20196</a>, which describes a similar issue
with an old non-C11-compliant Clang and a C11-relying GNU libstdc++.</pre>
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