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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [-fms-compatibility] Allow ICE pointer values in case labels"
href="http://llvm.org/bugs/show_bug.cgi?id=16034">16034</a>
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<th>Summary</th>
<td>[-fms-compatibility] Allow ICE pointer values in case labels
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Frontend
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>reid.kleckner@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>MSVC accepts this code:
typedef void *HKEY;
#define HKEY_CLASSES_ROOT (( HKEY ) (ULONG_PTR)((LONG)0x80000000) )
...
const wchar_t *HKEYToString(const HKEY key) {
switch (reinterpret_cast<LONG_PTR>(key)) {
case HKEY_CLASSES_ROOT:
return L"HKEY_CLASSES_ROOT";
case HKEY_CURRENT_CONFIG:
return L"HKEY_CURRENT_CONFIG";
case HKEY_CURRENT_USER:
return L"HKEY_CURRENT_USER";
case HKEY_LOCAL_MACHINE:
return L"HKEY_LOCAL_MACHINE";
case HKEY_USERS:
return L"HKEY_USERS";
}
return L"unknown";
}
It does not accept 'switch (key)', so it must be converting the case label
values to LONG_PTR.
If I try to cast the label values back to LONG_PTR, clang says reinterpret_cast
conversions are not allowed in case labels:
registry.cc:24:10: error: case value is not a constant expression
case (LONG_PTR)HKEY_USERS:
^~~~~~~~~~~~~~~~~~~~
registry.cc:24:10: note: cast that performs the conversions of a
reinterpret_cast is not allowed in a constant expression
It seems the least invasive way to get clang to accept this code is to fall
back to an if/else chain, unless clang adds support for this as an extension.</pre>
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