test/Parser/ms-empty-enum.c

// RUN: %clang_cc1 %s -fsyntax-only -Wmicrosoft -verify -fms-extensions

typedef enum tag1 { } A; // expected-warning {{empty enumeration types are a Microsoft extension}}
typedef enum tag2 { } B; // expected-warning {{empty enumeration types are a Microsoft extension}}
typedef enum : unsigned { } C; // expected-warning {{enumeration types with a fixed underlying type are a Microsoft extension}}\
                               // expected-warning {{empty enumeration types are a Microsoft extension}}