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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - -Wcast-qual should not warn about dropping 'const' when casting to ObjC types"
href="https://bugs.llvm.org/show_bug.cgi?id=33929">33929</a>
</td>
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<th>Summary</th>
<td>-Wcast-qual should not warn about dropping 'const' when casting to ObjC types
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>MacOS X
</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>
<tr>
<th>Reporter</th>
<td>jordan_rose@apple.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>// clang -fsyntax-only -x objective-c -Weverything -
id reinterpretAsObject(const void *ptr) {
return (id)ptr;
}
<stdin>:2:14: warning: cast from 'const void *' to 'id' drops const qualifier
[-Wcast-qual]
return (id)ptr;
^
...however, there's no way to avoid this warning; you can't const-qualify
Objective-C object types inside the pointer. It might have been better if this
weren't a common idiom on Apple platforms, but it is---both 'const void *' and
opaque pointers to const struct types are sometimes valid Objective-C objects,
and casts to 'id', 'Class', or concrete object pointer types like 'NSString *'
are considered common and acceptable.
(If we /were/ to start warning on these all the time, they should be silenced
by adding '__bridge', and the warning should have a fix-it. But even that's
probably too much churn for Apple platforms.)</pre>
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