Added fclose_deleter.

fclose_deleter can be used as a deleter function object for std::FILE
pointers returned by std::fopen.

test/fclose_deleter_test.cpp

@@ -0,0 +1,52 @@
+/*
+ *             Copyright Andrey Semashev 2022.
+ * 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)
+ */
+/*!
+ * \file   fclose_deleter_test.cpp
+ * \author Andrey Semashev
+ * \date   21.09.2022
+ *
+ * This file contains tests for \c boost::fclose_deleter.
+ */
+
+#include <boost/core/fclose_deleter.hpp>
+#include <cstdio>
+#include <cstddef>
+#include <boost/config.hpp>
+#if !defined(BOOST_NO_CXX11_SMART_PTR)
+#include <memory>
+#endif
+
+#if !defined(BOOST_NO_CXX11_SMART_PTR)
+std::unique_ptr< std::FILE, boost::fclose_deleter > make_unique_file(const char* filename)
+{
+    return std::unique_ptr< std::FILE, boost::fclose_deleter >(std::fopen(filename, "w"));
+}
+
+std::shared_ptr< std::FILE > make_shared_file(const char* filename)
+{
+    return std::shared_ptr< std::FILE >(std::fopen(filename, "w"), boost::fclose_deleter());
+}
+#endif
+
+int main()
+{
+    const char* const filename = "fcd_test.txt";
+
+    std::FILE* file = std::fopen(filename, "w");
+    if (file)
+    {
+        boost::fclose_deleter()(file);
+        file = NULL;
+    }
+
+#if !defined(BOOST_NO_CXX11_SMART_PTR)
+    make_unique_file(filename);
+    make_shared_file(filename);
+#endif
+
+    std::remove(filename);
+}