Sync 'in class initialization of static const double' extension up with GCC,

and split it out of -Wgnu into its own warning flag.

 * In C++11, this is now a hard error (GCC has no extension here in C++11 mode).
   The error can be disabled with -Wno-static-float-init, and has a fixit to
   add 'constexpr'.

 * In C++98, this is still an ExtWarn, but is now controlled by
   -Wstatic-float-init as well as -Wgnu.

llvm-svn: 173414

clang/include/clang/Basic/DiagnosticGroups.td

@@ -212,6 +212,8 @@ def : DiagGroup<"synth">;
 def SizeofArrayArgument : DiagGroup<"sizeof-array-argument">;
 def SizeofPointerMemaccess : DiagGroup<"sizeof-pointer-memaccess">;
 def StaticInInline : DiagGroup<"static-in-inline">;
+def GNUStaticFloatInit : DiagGroup<"gnu-static-float-init">;
+def StaticFloatInit : DiagGroup<"static-float-init", [GNUStaticFloatInit]>;
 def StringPlusInt : DiagGroup<"string-plus-int">;
 def StrncatSize : DiagGroup<"strncat-size">;
 def TautologicalOutOfRangeCompare : DiagGroup<"tautological-constant-out-of-range-compare">;
@@ -474,7 +476,8 @@ def C11 : DiagGroup<"c11-extensions">;
 def C99 : DiagGroup<"c99-extensions">;
 
 // A warning group for warnings about GCC extensions.
-def GNU : DiagGroup<"gnu", [GNUDesignator, VLAExtension, ZeroLengthArray]>;
+def GNU : DiagGroup<"gnu", [GNUDesignator, VLAExtension,
+                            ZeroLengthArray, GNUStaticFloatInit]>;
 // A warning group for warnings about code that clang accepts but gcc doesn't.
 def GccCompat : DiagGroup<"gcc-compat">;
 

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -5304,9 +5304,10 @@ def err_in_class_initializer_bad_type : Error<
   "static data member of type %0 must be initialized out of line">;
 def ext_in_class_initializer_float_type : ExtWarn<
   "in-class initializer for static data member of type %0 is a GNU extension">,
-  InGroup<GNU>;
-def note_in_class_initializer_float_type_constexpr : Note<
-  "use 'constexpr' specifier to silence this warning">;
+  InGroup<GNUStaticFloatInit>;
+def ext_in_class_initializer_float_type_cxx11 : ExtWarn<
+  "in-class initializer for static data member of type %0 requires "
+  "'constexpr' specifier">, InGroup<StaticFloatInit>, DefaultError;
 def err_in_class_initializer_literal_type : Error<
   "in-class initializer for static data member of type %0 requires "
   "'constexpr' specifier">;

clang/lib/Sema/SemaDecl.cpp

@@ -7128,17 +7128,23 @@ void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init,
 
     // We allow foldable floating-point constants as an extension.
     } else if (DclT->isFloatingType()) { // also permits complex, which is ok
-      Diag(VDecl->getLocation(), diag::ext_in_class_initializer_float_type)
-        << DclT << Init->getSourceRange();
-      if (getLangOpts().CPlusPlus11)
+      // In C++98, this is a GNU extension. In C++11, it is not, but we support
+      // it anyway and provide a fixit to add the 'constexpr'.
+      if (getLangOpts().CPlusPlus11) {
         Diag(VDecl->getLocation(),
-             diag::note_in_class_initializer_float_type_constexpr)
+             diag::ext_in_class_initializer_float_type_cxx11)
+          << DclT << Init->getSourceRange()
           << FixItHint::CreateInsertion(VDecl->getLocStart(), "constexpr ");
+        VDecl->setConstexpr(true);
+      } else {
+        Diag(VDecl->getLocation(), diag::ext_in_class_initializer_float_type)
+          << DclT << Init->getSourceRange();
 
-      if (!Init->isValueDependent() && !Init->isEvaluatable(Context)) {
-        Diag(Init->getExprLoc(), diag::err_in_class_initializer_non_constant)
-          << Init->getSourceRange();
-        VDecl->setInvalidDecl();
+        if (!Init->isValueDependent() && !Init->isEvaluatable(Context)) {
+          Diag(Init->getExprLoc(), diag::err_in_class_initializer_non_constant)
+            << Init->getSourceRange();
+          VDecl->setInvalidDecl();
+        }
       }
 
     // Suggest adding 'constexpr' in C++11 for literal types.

clang/test/CXX/class/class.static/class.static.data/p3.cpp

@@ -13,7 +13,7 @@ struct S {
   static const int d2 = 0;
 
   static constexpr double e = 0.0; // ok
-  static const double f = 0.0; // expected-warning {{extension}} expected-note {{use 'constexpr' specifier}}
+  static const double f = 0.0; // expected-error {{requires 'constexpr' specifier}}
   static char *const g = 0; // expected-error {{requires 'constexpr' specifier}}
   static const NonLit h = NonLit(); // expected-error {{must be initialized out of line}}
 };

clang/test/CXX/class/class.union/p2-0x.cpp

@@ -7,7 +7,7 @@ union U1 {
   static const int k2 = k1;
   static int k3 = k2; // expected-error {{non-const static data member must be initialized out of line}}
   static constexpr double k4 = k2;
-  static const double k5 = k4; // expected-warning {{GNU extension}} expected-note {{use 'constexpr'}}
+  static const double k5 = k4; // expected-error {{requires 'constexpr' specifier}}
   int n[k1 + 3];
 };
 

clang/test/SemaCXX/cxx0x-class.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s 
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -Wno-error=static-float-init %s 
 
 int vs = 0;
 
@@ -17,11 +17,11 @@ public:
 };
 
 namespace rdar8367341 {
-  float foo(); // expected-note {{here}}
+  float foo(); // expected-note 2{{here}}
 
   struct A {
-    static const float x = 5.0f; // expected-warning {{GNU extension}} expected-note {{use 'constexpr' specifier to silence this warning}}
-    static const float y = foo(); // expected-warning {{GNU extension}} expected-note {{use 'constexpr' specifier to silence this warning}} expected-error {{in-class initializer for static data member is not a constant expression}}
+    static const float x = 5.0f; // expected-warning {{requires 'constexpr'}}
+    static const float y = foo(); // expected-warning {{requires 'constexpr'}} expected-error {{constexpr variable 'y' must be initialized by a constant expression}} expected-note {{non-constexpr function 'foo'}}
     static constexpr float x2 = 5.0f;
     static constexpr float y2 = foo(); // expected-error {{must be initialized by a constant expression}} expected-note {{non-constexpr function 'foo'}}
   };

clang/test/SemaCXX/warn-static-const-float.cpp

@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -verify %s -std=c++98 -DEXT
+// RUN: %clang_cc1 -verify %s -std=c++98 -Wno-gnu -DNONE
+// RUN: %clang_cc1 -verify %s -std=c++98 -Wno-static-float-init -DNONE
+// RUN: %clang_cc1 -verify %s -std=c++98 -Wno-gnu-static-float-init -DNONE
+// RUN: %clang_cc1 -verify %s -std=c++11 -DERR
+// RUN: %clang_cc1 -verify %s -std=c++11 -Wno-gnu -DERR
+// RUN: %clang_cc1 -verify %s -std=c++11 -Wno-static-float-init -DNONE
+// RUN: %clang_cc1 -verify %s -std=c++11 -Wno-gnu-static-float-init -DERR
+
+#if NONE
+// expected-no-diagnostics
+#elif ERR
+// expected-error@19 {{in-class initializer for static data member of type 'const double' requires 'constexpr' specifier}}
+#elif EXT
+// expected-warning@19 {{in-class initializer for static data member of type 'const double' is a GNU extension}}
+#endif
+
+struct X {
+  static const double x = 0.0;
+};