Enforce restrictions that 'main' is not allowed to be deleted, or to be used by
the program, in C++. (We allow the latter as an extension, since we've always
permitted it, and GCC does the same, and our supported C++ ABIs don't do
anything special in main.)

llvm-svn: 199782
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 39d71e2..76b9d66 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -11984,6 +11984,11 @@
     }
   }
 
+  // C++11 [basic.start.main]p3:
+  //   A program that defines main as deleted [...] is ill-formed.
+  if (Fn->isMain())
+    Diag(DelLoc, diag::err_deleted_main);
+
   Fn->setDeletedAsWritten();
 }