From bff62031529e651942326b13596b34fd4d96bac7 Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Thu, 21 Oct 2010 16:57:46 +0000
Subject: [PATCH] Always treat 'main' as an extern "C" function, so that we
 detect redeclarations of main appropriately rather than allowing it to be
 overloaded. Also, disallowing declaring main as a template.

Fixes GCC DejaGNU g++.old-deja/g++.other/main1.C.

llvm-svn: 117029
---
 clang/include/clang/Basic/DiagnosticSemaKinds.td          | 1 +
 clang/include/clang/Sema/Sema.h                           | 2 +-
 clang/lib/AST/Decl.cpp                                    | 2 +-
 clang/lib/Sema/SemaDecl.cpp                               | 5 +++++
 clang/test/CXX/basic/basic.start/basic.start.main/p2h.cpp | 5 +++++
 5 files changed, 13 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/CXX/basic/basic.start/basic.start.main/p2h.cpp

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 9008b346c92a..87d2a9f81f8b 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -229,6 +229,7 @@ def warn_unusual_main_decl : Warning<"'main' should not be declared "
     "%select{static|inline|static or inline}0">;
 def err_unusual_main_decl : Error<"'main' is not allowed to be declared "
     "%select{static|inline|static or inline}0">;
+def err_main_template_decl : Error<"'main' cannot be a template">;
 def err_main_returns_nonint : Error<"'main' must return 'int'">;
 def err_main_surplus_args : Error<"too many parameters (%0) for 'main': "
     "must be 0, 2, or 3">;
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 108353f53b00..7670316b9d7d 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -964,7 +964,7 @@ public:
     Ovl_NonFunction
   };
   OverloadKind CheckOverload(Scope *S,
-                             FunctionDecl *New,
+                             FunctionDecl *New, 
                              const LookupResult &OldDecls,
                              NamedDecl *&OldDecl,
                              bool IsForUsingDecl);
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 4898d6f2fc0c..5a1edbd0e671 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -1001,7 +1001,7 @@ bool FunctionDecl::isExternC() const {
       break;
   }
 
-  return false;
+  return isMain();
 }
 
 bool FunctionDecl::isGlobal() const {
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 57cbb46480b0..f1045d3c0b7a 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -4182,6 +4182,11 @@ void Sema::CheckMain(FunctionDecl* FD) {
   if (nparams == 1 && !FD->isInvalidDecl()) {
     Diag(FD->getLocation(), diag::warn_main_one_arg);
   }
+  
+  if (!FD->isInvalidDecl() && FD->getDescribedFunctionTemplate()) {
+    Diag(FD->getLocation(), diag::err_main_template_decl);
+    FD->setInvalidDecl();
+  }
 }
 
 bool Sema::CheckForConstantInitializer(Expr *Init, QualType DclT) {
diff --git a/clang/test/CXX/basic/basic.start/basic.start.main/p2h.cpp b/clang/test/CXX/basic/basic.start/basic.start.main/p2h.cpp
new file mode 100644
index 000000000000..abf8faa968cf
--- /dev/null
+++ b/clang/test/CXX/basic/basic.start/basic.start.main/p2h.cpp
@@ -0,0 +1,5 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s 
+
+template<typename T>
+int main() { } // expected-error{{'main' cannot be a template}}
+
-- 
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