Merge [52454] to release. Fixes #2951.

[SVN r52472]

include/boost/smart_ptr/shared_ptr.hpp

@@ -277,7 +277,7 @@ public:
 #if !defined( BOOST_NO_SFINAE ) && !defined( BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION )
 
     template<class Ap>
-    shared_ptr( Ap r, typename boost::detail::sp_enable_if_auto_ptr<Ap, int>::type = 0 ): px( r.get() ), pn()
+    explicit shared_ptr( Ap r, typename boost::detail::sp_enable_if_auto_ptr<Ap, int>::type = 0 ): px( r.get() ), pn()
     {
         typename Ap::element_type * tmp = r.get();
         pn = boost::detail::shared_count( r );

test/Jamfile.v2

@@ -56,5 +56,6 @@ import testing ;
           [ run sp_recursive_assign2_test.cpp ]
           [ run sp_recursive_assign_rv_test.cpp ]
           [ run sp_recursive_assign2_rv_test.cpp ]
+          [ compile-fail auto_ptr_lv_fail.cpp ]
         ;
 }

test/auto_ptr_lv_fail.cpp

@@ -0,0 +1,32 @@
+#include <boost/config.hpp>
+
+#if defined(BOOST_MSVC)
+#pragma warning(disable: 4786)  // identifier truncated in debug info
+#pragma warning(disable: 4710)  // function not inlined
+#pragma warning(disable: 4711)  // function selected for automatic inline expansion
+#pragma warning(disable: 4514)  // unreferenced inline removed
+#endif
+
+//
+//  auto_ptr_lv_fail.cpp - a negative test for converting an auto_ptr to shared_ptr
+//
+//  Copyright 2009 Peter Dimov
+//
+//  Distributed under the Boost Software License, Version 1.0.
+//  See accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt
+//
+
+#include <boost/shared_ptr.hpp>
+#include <memory>
+
+void f( boost::shared_ptr<int> )
+{
+}
+
+int main()
+{
+    std::auto_ptr<int> p;
+    f( p ); // must fail
+    return 0;
+}