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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/107164] No pedantic warning for declaration just referring to
 a previously-declared enum type
Date: Wed, 05 Oct 2022 22:05:22 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107164

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
clang says it is a GCC extension:
<source>:2:6: warning: redeclaration of already-defined enum 'E' is a GNU
extension [-Wgnu-redeclared-enum]
enum E;
     ^
<source>:1:6: note: previous definition is here
enum E {a,b,c};
     ^

GCC does have a forward declaration extension for enum types so it makes se=
nse
to allow this as an extension too.

That is:
```
enum E;
enum E {a,b,c};
```

(which GCC does have a pedantic diagnostic about).=