From: John McCall <rjmccall@apple.com>
Date: Sat, 26 Mar 2011 02:09:52 +0000 (+0000)
Subject: Don't warn about the 'extern' in 'extern "C"' on a tag decl.   This is
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=379246d29b1c7ef2659beadf41b4cb79806c0e63;p=clang

Don't warn about the 'extern' in 'extern "C"' on a tag decl.   This is
usually useless, but not always.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@128326 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 5a4df400f3..59b4f5f229 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1870,9 +1870,14 @@ Decl *Sema::ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS,
   if (emittedWarning || (TagD && TagD->isInvalidDecl()))
     return TagD;
 
+  // Note that a linkage-specification sets a storage class, but
+  // 'extern "C" struct foo;' is actually valid and not theoretically
+  // useless.
   if (DeclSpec::SCS scs = DS.getStorageClassSpec())
-    Diag(DS.getStorageClassSpecLoc(), diag::warn_standalone_specifier)
-      << DeclSpec::getSpecifierName(scs);
+    if (!DS.isExternInLinkageSpec())
+      Diag(DS.getStorageClassSpecLoc(), diag::warn_standalone_specifier)
+        << DeclSpec::getSpecifierName(scs);
+
   if (DS.isThreadSpecified())
     Diag(DS.getThreadSpecLoc(), diag::warn_standalone_specifier) << "__thread";
   if (DS.getTypeQualifiers()) {
diff --git a/test/SemaCXX/storage-class.cpp b/test/SemaCXX/storage-class.cpp
index a2e206323a..01cfbfc51f 100644
--- a/test/SemaCXX/storage-class.cpp
+++ b/test/SemaCXX/storage-class.cpp
@@ -2,3 +2,6 @@
 extern const int PR6495a = 42;
 extern int PR6495b = 42; // expected-warning{{'extern' variable has an initializer}}
 extern const int PR6495c[] = {42,43,44};
+
+extern struct Test1 {}; // expected-warning {{'extern' ignored on this declaration}}
+extern "C" struct Test0 {}; // no warning