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+// Copyright (C) 2011-2015 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef UTIL_UNITTESTS_NEWHOOK_H
+#define UTIL_UNITTESTS_NEWHOOK_H 1
+
+/**
+ * \file newhook.h
+ * \brief Enable the use of special operator new that throws for testing.
+ *
+ * This small utility allows a test case to force the global operator new
+ * to throw for a given size to test a case where memory allocation fails
+ * (which normally doesn't happen).  To enable the feature, everything must
+ * be built with defining ENABLE_CUSTOM_OPERATOR_NEW beforehand, and set
+ * \c force_throw_on_new to \c true and \c throw_size_on_new to the size
+ * of data that should trigger the exception, immediately before starting
+ * the specific test that needs the exception.
+ *
+ * Example:
+ * \code #include <util/unittests/newhook.h>
+ * ...
+ * TEST(SomeTest, newException) {
+ *        isc::util::unittests::force_throw_on_new = true;
+ *        isc::util::unittests::throw_size_on_new = sizeof(Foo);
+ *        try {
+ *            // this will do 'new Foo()' internally and should throw
+ *            createFoo();
+ *            isc::util::unittests::force_throw_on_new = false;
+ *            ASSERT_FALSE(true) << "Expected throw on new";
+ *        } catch (const std::bad_alloc&) {
+ *            isc::util::unittests::force_throw_on_new = false;
+ *            // do some integrity check, etc, if necessary
+ *        }
+ * } \endcode
+ *
+ * Replacing the global operator new (and delete) is a dangerous technique,
+ * and triggering an exception solely based on the allocation size is not
+ * reliable, so this feature is disabled by default two-fold: The
+ * ENABLE_CUSTOM_OPERATOR_NEW build time variable, and run-time
+ * \c force_throw_on_new.
+ */
+
+namespace isc {
+namespace util {
+namespace unittests {
+/// Switch to enable the use of special operator new
+///
+/// This is set to \c false by default.
+extern bool force_throw_on_new;
+
+/// The allocation size that triggers an exception in the special operator new
+///
+/// This is the exact size that causes an exception to be thrown;
+/// for example, if it is set to 100, an attempt of allocating 100 bytes
+/// will result in an exception, but allocation attempt for 101 bytes won't
+/// (unless, of course, memory is really exhausted and allocation really
+/// fails).
+///
+/// The default value is 0.  The value of this variable has no meaning
+/// unless the use of the special operator is enabled at build time and
+/// via \c force_throw_on_new.
+extern size_t throw_size_on_new;
+}
+}
+}
+
+#endif // UTIL_UNITTESTS_NEWHOOK_H
+
+// Local Variables:
+// mode: c++
+// End: