Emit -Wmicrosoft-enum-value warning instead of error in MS ABI

Summary:
The first NFC change is to replace a getCXXABI().isMicrosoft() check
with getTriple().isWindowsMSVCEnvironment(). This code takes effect in
non-C++ compilations, so it doesn't make sense to check the C++ ABI. In
the MS ABI, enums are always considered to be "complete" because the
underlying type of an unfixed enum will always be 'int'. This behavior
was moved from -fms-compatibility to MS ABI back in r249656.

The second change is functional, and it downgrades an error to a warning
when the MS ABI is used rather than only under -fms-compatibility. The
reasoning is that it's unreasonable for the following code to reject the
following code for all MS ABI targets with -fno-ms-compatibility:
  enum Foo { Foo_Val = 0xDEADBEEF };
This is valid code for any other target, but in the MS ABI, Foo_Val just
happens to be negative. With this change, clang emits a
-Wmicrosoft-enum-value warning on this code, but compiles it without
error.

Fixes PR38478

Reviewers: hans, rsmith, STL_MSFT

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D67304

llvm-svn: 371581

1 files changed, 13 insertions, 1 deletions

diff --git a/clang/test/Sema/MicrosoftCompatibility.c b/clang/test/Sema/MicrosoftCompatibility.c
index 697d3f21663..9a1f050747f 100644
--- a/clang/test/Sema/MicrosoftCompatibility.c
+++ b/clang/test/Sema/MicrosoftCompatibility.c
@@ -1,10 +1,18 @@
-// RUN: %clang_cc1 %s -fsyntax-only -Wno-unused-value -Wmicrosoft -verify -fms-compatibility -triple i686-pc-win32
+// RUN: %clang_cc1 %s -fsyntax-only -Wno-unused-value -Wmicrosoft -verify -fms-compatibility -DMSVCCOMPAT -triple i686-pc-win32
+// RUN: %clang_cc1 %s -fsyntax-only -Wno-unused-value -Wmicrosoft -verify -fms-extensions -triple i686-pc-win32
 
+#ifdef MSVCCOMPAT
 enum ENUM1; // expected-warning {{forward references to 'enum' types are a Microsoft extension}}
 enum ENUM1 var1 = 3;
 enum ENUM1* var2 = 0;
+#else
+enum ENUM1; // expected-note {{forward declaration of}}
+enum ENUM1 var1 = 3; // expected-error {{variable has incomplete type 'enum ENUM1'}}
+enum ENUM1* var2 = 0;
+#endif
 
 
+// FIXME: The rest of this seems to be controlled by -fms-extensions. Move it.
 enum ENUM2 {
   ENUM2_a = (enum ENUM2) 4,
   ENUM2_b = 0x9FFFFFFF, // expected-warning {{enumerator value is not representable in the underlying type 'int'}}
@@ -22,4 +30,8 @@ struct __declspec(appdomain) S3 {}; /* expected-warning {{__declspec attribute '
 
 __declspec(__noreturn__) void f7(void); /* expected-warning {{__declspec attribute '__noreturn__' is not supported}} */
 
+#ifdef MSVCCOMPAT
 size_t x;
+#else
+size_t x; // expected-error {{unknown type name 'size_t'}}
+#endif