Add a getLanguageLinkage method to VarDecls and FunctionDecls. Use it to fix

some cases where functions with no language linkage were being treated as having
C language linkage. In particular, don't warn in

extern "C" {
  static NonPod foo();
}

Since getLanguageLinkage checks the language linkage, the linkage computation
cannot use the language linkage. Break the loop by checking just the context
in the linkage computation.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175117 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 24 insertions, 10 deletions

diff --git a/include/clang/AST/Decl.h b/include/clang/AST/Decl.h
index b6a650fea3..947525f691 100644
--- a/include/clang/AST/Decl.h
+++ b/include/clang/AST/Decl.h
@@ -898,11 +898,12 @@ public:
   /// external, C linkage.
   bool isExternC() const;
 
-  /// Checks if this variable has C language linkage. Note that this is not the
-  /// same as isExternC since decls with non external linkage can have C
-  /// language linkage. They can also have C language linkage when they are not
-  /// declared in an extern C context, but a previous decl is.
-  bool hasCLanguageLinkage() const;
+  /// Compute the language linkage.
+  LanguageLinkage getLanguageLinkage() const;
+
+  bool hasCLanguageLinkage() const {
+    return getLanguageLinkage() == CLanguageLinkage;
+  }
 
   /// isLocalVarDecl - Returns true for local variable declarations
   /// other than parameters.  Note that this includes static variables
@@ -1790,11 +1791,12 @@ public:
   /// external, C linkage.
   bool isExternC() const;
 
-  /// Checks if this function has C language linkage. Note that this is not the
-  /// same as isExternC since decls with non external linkage can have C
-  /// language linkage. They can also have C language linkage when they are not
-  /// declared in an extern C context, but a previous decl is.
-  bool hasCLanguageLinkage() const;
+  /// Compute the language linkage.
+  LanguageLinkage getLanguageLinkage() const;
+
+  bool hasCLanguageLinkage() const {
+    return getLanguageLinkage() == CLanguageLinkage;
+  }
 
   /// \brief Determines whether this is a global function.
   bool isGlobal() const;
diff --git a/include/clang/AST/DeclBase.h b/include/clang/AST/DeclBase.h
index 5a9e9fedfa..3248d23f42 100644
--- a/include/clang/AST/DeclBase.h
+++ b/include/clang/AST/DeclBase.h
@@ -1090,6 +1090,10 @@ public:
   /// a C++ extern "C" linkage spec.
   bool isExternCContext() const;
 
+  /// \brief Determines whether this context is, or is nested within,
+  /// a C++ extern "C++" linkage spec.
+  bool isExternCXXContext() const;
+
   /// \brief Determine whether this declaration context is equivalent
   /// to the declaration context DC.
   bool Equals(const DeclContext *DC) const {
diff --git a/include/clang/Basic/Linkage.h b/include/clang/Basic/Linkage.h
index 6bc1f5d5ef..01b8db15f5 100644
--- a/include/clang/Basic/Linkage.h
+++ b/include/clang/Basic/Linkage.h
@@ -42,6 +42,14 @@ enum Linkage {
   ExternalLinkage
 };
 
+/// \brief Describes the different kinds of language linkage
+/// (C++ [dcl.link]) that an entity may have.
+enum LanguageLinkage {
+  CLanguageLinkage,
+  CXXLanguageLinkage,
+  NoLanguageLinkage
+};
+
 /// \brief A more specific kind of linkage than enum Linkage.
 ///
 /// This is relevant to CodeGen and AST file reading.