From f411196d15a92f415d6a042b787f8fccc1ffec42 Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Thu, 20 Oct 2011 18:35:58 +0000
Subject: [PATCH] 'extern template' is a C++11 feature. Add an Extension for
 C++98 (this matches gcc's behaviour), and a -Wc++98-compat-pedantic warning
 for C++11.

llvm-svn: 142597
---
 clang/include/clang/Basic/DiagnosticParseKinds.td  | 5 +++++
 clang/lib/Parse/Parser.cpp                         | 3 +++
 clang/test/CXX/temp/temp.spec/temp.explicit/p4.cpp | 2 +-
 clang/test/SemaCXX/cxx98-compat-pedantic.cpp       | 3 +++
 4 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td
index 62470582870c..32e9a0837014 100644
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -469,6 +469,11 @@ def err_missing_dependent_template_keyword : Error<
 def warn_missing_dependent_template_keyword : ExtWarn<
   "use 'template' keyword to treat '%0' as a dependent template name">;
 
+def ext_extern_template : Extension<
+  "extern templates are a C++11 extension">, InGroup<CXX11>;
+def warn_cxx98_compat_extern_template : Warning<
+  "extern templates are incompatible with C++98">,
+  InGroup<CXX98CompatPedantic>, DefaultIgnore;
 def warn_static_inline_explicit_inst_ignored : Warning<
   "ignoring '%select{static|inline}0' keyword on explicit template "
   "instantiation">;
diff --git a/clang/lib/Parse/Parser.cpp b/clang/lib/Parse/Parser.cpp
index 2a1e2a2de899..2e0c46dbdbfe 100644
--- a/clang/lib/Parse/Parser.cpp
+++ b/clang/lib/Parse/Parser.cpp
@@ -642,6 +642,9 @@ Parser::ParseExternalDeclaration(ParsedAttributesWithRange &attrs,
       // Extern templates
       SourceLocation ExternLoc = ConsumeToken();
       SourceLocation TemplateLoc = ConsumeToken();
+      Diag(ExternLoc, getLang().CPlusPlus0x ?
+             diag::warn_cxx98_compat_extern_template :
+             diag::ext_extern_template) << SourceRange(ExternLoc, TemplateLoc);
       SourceLocation DeclEnd;
       return Actions.ConvertDeclToDeclGroup(
                   ParseExplicitInstantiation(ExternLoc, TemplateLoc, DeclEnd));
diff --git a/clang/test/CXX/temp/temp.spec/temp.explicit/p4.cpp b/clang/test/CXX/temp/temp.spec/temp.explicit/p4.cpp
index d30437411513..09c428e01df3 100644
--- a/clang/test/CXX/temp/temp.spec/temp.explicit/p4.cpp
+++ b/clang/test/CXX/temp/temp.spec/temp.explicit/p4.cpp
@@ -43,6 +43,6 @@ namespace test0 {
     // inappropriately instantiating this template.
     void *ptr = x;
   }
-  extern template class foo<char>;
+  extern template class foo<char>; // expected-warning {{extern templates are a C++11 extension}}
   template class foo<char>;
 }
diff --git a/clang/test/SemaCXX/cxx98-compat-pedantic.cpp b/clang/test/SemaCXX/cxx98-compat-pedantic.cpp
index 28fc23a0a763..00532d5ac073 100644
--- a/clang/test/SemaCXX/cxx98-compat-pedantic.cpp
+++ b/clang/test/SemaCXX/cxx98-compat-pedantic.cpp
@@ -29,3 +29,6 @@ struct ConvertToInt {
   operator int();
 };
 int *ArraySizeConversion = new int[ConvertToInt()]; // expected-warning {{implicit conversion from array size expression of type 'ConvertToInt' to integral type 'int' is incompatible with C++98}}
+
+template<typename T> class ExternTemplate {};
+extern template class ExternTemplate<int>; // expected-warning {{extern templates are incompatible with C++98}}
-- 
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