Type::isArithmeticType(): disallow incomplete enum decls.

Bug submitted by Eli.

llvm-svn: 46102

Author: Steve Naroff

clang/AST/Type.cpp

@@ -444,8 +444,11 @@ bool Type::isArithmeticType() const {
   if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
     return BT->getKind() != BuiltinType::Void;
   if (const TagType *TT = dyn_cast<TagType>(CanonicalType))
-    if (TT->getDecl()->getKind() == Decl::Enum)
-      return true;
+    if (const EnumDecl *ED = dyn_cast<EnumDecl>(TT->getDecl()))
+      // GCC allows forward declaration of enum types (forbid by C99 6.7.2.3p2).
+      // If a body isn't seen by the time we get here, we exclude it from
+      // being allowed in arithmetic expressions.
+      return ED->isDefinition();
   return isa<ComplexType>(CanonicalType) || isa<VectorType>(CanonicalType);
 }
 

clang/include/clang/AST/Decl.h

@@ -663,6 +663,7 @@ class EnumDecl : public TagDecl {
   EnumDecl(SourceLocation L, IdentifierInfo *Id, ScopedDecl *PrevDecl)
     : TagDecl(Enum, L, Id, PrevDecl) {
     ElementList = 0;
+	IntegerType = QualType();
   }
 
   /// defineElements - When created, EnumDecl correspond to a forward declared

clang/test/Sema/enum.c

@@ -22,3 +22,9 @@ int test() {
   return sizeof(enum e) ;
 }
 
+enum gccForwardEnumExtension ve; // expected-warning {{ISO C forbids forward references to 'enum' types}}
+
+int test2(int i)
+{
+  ve + i; // expected-error{{invalid operands to binary expression ('enum gccForwardEnumExtension' and 'int')}}
+}