From aa71567ba4b8a10e9a7d668bf93e35413d7260a8 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Wed, 29 May 2013 00:56:45 +0000
Subject: [PATCH] Disallow extern decls of type void in C++ mode

C++ and C differ with respect to the handling of extern void
declarations. Enforce the C++ behavior in C++ mode.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182814 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaDecl.cpp                | 14 +++++++++-----
 test/SemaCXX/linkage-spec.cpp        |  2 ++
 test/SemaCXX/qualified-id-lookup.cpp |  2 +-
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 49c8fe5e71..05748f72f4 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -5271,11 +5271,15 @@ void Sema::CheckVariableDeclarationType(VarDecl *NewVD) {
     NewVD->setTypeSourceInfo(FixedTInfo);
   }
 
-  if (T->isVoidType() && NewVD->isThisDeclarationADefinition()) {
-    Diag(NewVD->getLocation(), diag::err_typecheck_decl_incomplete_type)
-      << T;
-    NewVD->setInvalidDecl();
-    return;
+  if (T->isVoidType()) {
+    // C++98 [dcl.stc]p5: The extern specifier can be applied only to the names
+    //                    of objects and functions.
+    if (NewVD->isThisDeclarationADefinition() || getLangOpts().CPlusPlus) {
+      Diag(NewVD->getLocation(), diag::err_typecheck_decl_incomplete_type)
+        << T;
+      NewVD->setInvalidDecl();
+      return;
+    }
   }
 
   if (!NewVD->hasLocalStorage() && NewVD->hasAttr<BlocksAttr>()) {
diff --git a/test/SemaCXX/linkage-spec.cpp b/test/SemaCXX/linkage-spec.cpp
index 504df0d35c..7681c7d847 100644
--- a/test/SemaCXX/linkage-spec.cpp
+++ b/test/SemaCXX/linkage-spec.cpp
@@ -114,3 +114,5 @@ namespace pr14958 {
   }
   int js::ObjectClass;
 }
+
+extern "C" void PR16167; // expected-error {{variable has incomplete type 'void'}}
diff --git a/test/SemaCXX/qualified-id-lookup.cpp b/test/SemaCXX/qualified-id-lookup.cpp
index a14193cc7a..26f1d7c472 100644
--- a/test/SemaCXX/qualified-id-lookup.cpp
+++ b/test/SemaCXX/qualified-id-lookup.cpp
@@ -149,6 +149,6 @@ namespace PR6830 {
 }
 
 namespace pr12339 {
-  extern "C" void i;
+  extern "C" void i; // expected-error{{variable has incomplete type 'void'}}
   pr12339::FOO  // expected-error{{no type named 'FOO' in namespace 'pr12339'}}
 }  // expected-error{{expected unqualified-id}}
-- 
2.50.1