Add multithreaded tests

test/shared_ptr_mt_test.cpp

@@ -0,0 +1,46 @@
+// Copyright 2018, 2020 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/shared_ptr.hpp>
+#include <boost/weak_ptr.hpp>
+#include <boost/smart_ptr/detail/lightweight_thread.hpp>
+#include <boost/bind/bind.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+static boost::shared_ptr<int> sp( new int );
+
+void f( int n )
+{
+    for( int i = 0; i < n; ++i )
+    {
+        boost::shared_ptr<int> p1( sp );
+        boost::weak_ptr<int> p2( p1 );
+    }
+}
+
+int main()
+{
+    int const N = 100000; // iterations
+    int const M = 8;      // threads
+
+    boost::detail::lw_thread_t th[ M ] = {};
+
+    for( int i = 0; i < M; ++i )
+    {
+        boost::detail::lw_thread_create( th[ i ], boost::bind( f, N ) );
+    }
+
+    for( int i = 0; i < M; ++i )
+    {
+        boost::detail::lw_thread_join( th[ i ] );
+    }
+
+    BOOST_TEST_EQ( sp.use_count(), 1 );
+
+    sp.reset();
+
+    BOOST_TEST_EQ( sp.use_count(), 0 );
+
+    return boost::report_errors();
+}