Add test that checks for duplicate category instances

test/Jamfile.v2

@@ -124,6 +124,15 @@ project
          [ run header_only_test.cpp
            :  :  : -<library>/boost/system//boost_system <define>BOOST_NO_ANSI_APIS : header_only_test_no_ansi
          ]
+         [ run single_instance_test.cpp single_instance_1.cpp single_instance_2.cpp
+           :  :  : <link>static : single_instance_test_static
+         ]
+         [ run single_instance_test.cpp single_instance_1.cpp single_instance_2.cpp
+           :  :  : <link>shared : single_instance_test_shared
+         ]
+         [ run single_instance_test.cpp single_instance_1.cpp single_instance_2.cpp
+           :  :  : -<library>/boost/system//boost_system <define>BOOST_ERROR_CODE_HEADER_ONLY : single_instance_test_header
+         ]
          ;
 
 # Quick (CI) test

test/single_instance_1.cpp

@@ -0,0 +1,22 @@
+
+// Copyright 2018 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+
+#include <boost/system/error_code.hpp>
+
+using namespace boost::system;
+
+namespace lib1
+{
+
+error_code get_system_code()
+{
+    return error_code( 0, system_category() );
+}
+
+error_code get_generic_code()
+{
+    return error_code( 0, generic_category() );
+}
+
+} // namespace lib1

test/single_instance_2.cpp

@@ -0,0 +1,22 @@
+
+// Copyright 2018 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+
+#include <boost/system/error_code.hpp>
+
+using namespace boost::system;
+
+namespace lib2
+{
+
+error_code get_system_code()
+{
+    return error_code( 0, system_category() );
+}
+
+error_code get_generic_code()
+{
+    return error_code( 0, generic_category() );
+}
+
+} // namespace lib2

test/single_instance_test.cpp

@@ -0,0 +1,32 @@
+
+// Copyright 2018 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+
+#include <boost/system/error_code.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+using namespace boost::system;
+
+namespace lib1
+{
+
+error_code get_system_code();
+error_code get_generic_code();
+
+} // namespace lib1
+
+namespace lib2
+{
+
+error_code get_system_code();
+error_code get_generic_code();
+
+} // namespace lib2
+
+int main()
+{
+    BOOST_TEST_EQ( lib1::get_system_code(), lib2::get_system_code() );
+    BOOST_TEST_EQ( lib1::get_generic_code(), lib2::get_generic_code() );
+
+    return boost::report_errors();
+}