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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - _MSVC_TRADITIONAL is missing in MSVC compatibility mode"
href="https://bugs.llvm.org/show_bug.cgi?id=47770">47770</a>
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<th>Summary</th>
<td>_MSVC_TRADITIONAL is missing in MSVC compatibility mode
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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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>jarccc7788@gmail.com
</td>
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<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>currently when -fms-compatibility is set it always uses a preprocessor
compatible with the traditional MSVC c-preprocessor.
since Visual Studio 2019 version 16.5 a predefined macro is used to detect
whether the compiler is using a conforming or the traditional c-preprocessor
'_MSVC_TRADITIONAL'.
<a href="https://docs.microsoft.com/en-us/cpp/preprocessor/preprocessor-experimental-overview?view=vs-2019">https://docs.microsoft.com/en-us/cpp/preprocessor/preprocessor-experimental-overview?view=vs-2019</a>
This macro is missing in clang when running in MSVC compatible mode.
this could (but probably won't) break compatibility with newer headers from the
Windows SDK.
the MSVC uses the new preprocessor when running with either /std:c11 or
/std:c17 where clang doesn't.
<a href="https://docs.microsoft.com/en-us/cpp/preprocessor/c-cpp-preprocessor-reference?view=vs-2019">https://docs.microsoft.com/en-us/cpp/preprocessor/c-cpp-preprocessor-reference?view=vs-2019</a></pre>
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