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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - elaborated-enum-base incompatible with NS_ENUM"
href="https://bugs.llvm.org/show_bug.cgi?id=49413">49413</a>
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<th>Summary</th>
<td>elaborated-enum-base incompatible with NS_ENUM
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>11.0
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>MacOS X
</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++
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>lhunath@lyndir.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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<pre>Related to
<a href="https://github.com/llvm/llvm-project/commit/c90e198107431f64b73686bdce31c293e3380ac7">https://github.com/llvm/llvm-project/commit/c90e198107431f64b73686bdce31c293e3380ac7</a>
The new `-Welaborated-enum-base` appears to be incompatible with macros to
define nonfixed type enums.
One such example is Apple's NS_ENUM, which effectively translates:
```
typedef NS_ENUM( X, unsigned int) {
...
}
```
into:
```
typedef enum X : unsigned int X;
enum X : unsigned int {
```
Which triggers:
```
fatal error: non-defining declaration of enumeration with a fixed underlying
type is only permitted as a standalone declaration; missing list of
enumerators? [-Welaborated-enum-base]
```
The idea behind macros such as `NS_ENUM` is that they type the enum if
supported by the compiler, as well as hide the `enum` type keyword.
Unfortunately, the only way to do this now would be to remove the nonfixed type
from the typedef, but this causes another problem:
```
error: enumeration previously declared with nonfixed underlying type
```
This can only be addressed by moving the typedef below the enum declaration,
but unfortunately it appears that this is impossible to achieve with a macro.
Consequently, `clang` can no longer compile `NS_ENUM`-style macros, and there
is no path for resolving the issue other than by disabling
`elaborated-enum-base`.</pre>
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