# HG changeset patch
# User mlarsson
# Date 1452782676 -3600
#      Thu Jan 14 15:44:36 2016 +0100
# Node ID d327697fe3dc3763b3043bd19456146671efaab0
# Parent  4dc2fc9888d226d2b88cf6a142aa7502fb9325dd
[mq]: 8146879

diff --git a/src/share/vm/logging/logFileOutput.cpp b/src/share/vm/logging/logFileOutput.cpp
--- a/src/share/vm/logging/logFileOutput.cpp
+++ b/src/share/vm/logging/logFileOutput.cpp
@@ -137,6 +137,10 @@
   if (!configure_rotation(options)) {
     return false;
   }
+
+  // Remove any existing log file in order to replace it (rather than append it)
+  remove(_file_name);
+
   _stream = fopen(_file_name, FileOpenMode);
   if (_stream == NULL) {
     log_error(logging)("Could not open log file '%s' (%s).\n", _file_name, strerror(errno));
diff --git a/test/serviceability/logging/TestLogTruncation.java b/test/serviceability/logging/TestLogTruncation.java
new file mode 100644
--- /dev/null
+++ b/test/serviceability/logging/TestLogTruncation.java
@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test TestLogTruncation
+ * @summary Ensure log files are truncated and not appended on VM startup
+ * @library /testlibrary
+ */
+
+import java.nio.file.Files;
+import java.nio.file.Paths;
+
+import jdk.test.lib.ProcessTools;
+import jdk.test.lib.OutputAnalyzer;
+
+import static jdk.test.lib.Asserts.assertEquals;
+
+public class TestLogTruncation {
+
+    public static void main(String[] args) throws Exception {
+        // Run two VMs with the same log file
+        for (int i = 0; i < 2; i++) {
+            ProcessBuilder pb = ProcessTools.createJavaProcessBuilder("-Xlog:logging=trace:out.log", "-version");
+            OutputAnalyzer output = new OutputAnalyzer(pb.start());
+            output.shouldHaveExitValue(0);
+        }
+
+        // Message should only appear once in the log file, since the second run should overwrite the previous log
+        long occurences = Files.lines(Paths.get("out.log"))
+                .filter(s -> s.contains("Log configuration fully initialized.")).count();
+        assertEquals(occurences, 1L, "Log file not truncated on VM startup");
+    }
+}
+