--- a/src/hotspot/share/utilities/vmError.cpp	Tue May 14 15:36:26 2019 +0200
+++ b/src/hotspot/share/utilities/vmError.cpp	Sun Apr 07 09:13:17 2019 +0200
@@ -1198,8 +1198,7 @@
 static int expand_and_open(const char* pattern, char* buf, size_t buflen, size_t pos) {
   int fd = -1;
   if (Arguments::copy_expand_pid(pattern, strlen(pattern), &buf[pos], buflen - pos)) {
-    // the O_EXCL flag will cause the open to fail if the file exists
-    fd = open(buf, O_RDWR | O_CREAT | O_EXCL, 0666);
+    fd = open(buf, O_RDWR | O_CREAT, 0666);
   }
   return fd;
 }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/jtreg/runtime/ErrorHandling/ErrorFileOverwriteTest.java	Sun Apr 07 09:13:17 2019 +0200
@@ -0,0 +1,162 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, SAP. 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
+ * @bug 8221738
+ * @summary Test that subsequent crashes will overwrite the file given to -XX:ErrorFile (unless %a is specified
+ *           in the error file name)
+ * @library /test/lib
+ * @modules java.base/jdk.internal.misc
+ * @requires (vm.debug == true)
+ */
+
+import jdk.test.lib.process.OutputAnalyzer;
+import jdk.test.lib.process.ProcessTools;
+
+import java.io.*;
+import java.util.regex.Pattern;
+
+public class ErrorFileOverwriteTest {
+
+  private static File findHsErrorFileInOutput(OutputAnalyzer output) {
+
+    String hs_err_file = output.firstMatch("# *(\\S*hs_err_pid.*\\.log)", 1);
+    if(hs_err_file ==null) {
+      throw new RuntimeException("Did not find hs-err file in output.\n");
+    }
+
+    File f = new File(hs_err_file);
+    if (!f.exists()) {
+      throw new RuntimeException("hs-err file missing at "
+              + f.getAbsolutePath() + ".\n");
+    }
+
+    return f;
+
+  }
+
+  private static void scanHsErrorFileForContent(File f, Pattern[] pattern) throws IOException {
+    FileInputStream fis = new FileInputStream(f);
+    BufferedReader br = new BufferedReader(new InputStreamReader(fis));
+    String line = null;
+
+    int currentPattern = 0;
+
+    String lastLine = null;
+    while ((line = br.readLine()) != null && currentPattern < pattern.length) {
+      if (pattern[currentPattern].matcher(line).matches()) {
+        System.out.println("Found: " + line + ".");
+        currentPattern++;
+      }
+      lastLine = line;
+    }
+    br.close();
+
+    if (currentPattern < pattern.length) {
+      throw new RuntimeException("hs-err file incomplete (first missing pattern: " +  pattern[currentPattern] + ")");
+    }
+
+  }
+
+  public static void do_test(boolean with_percent_p) throws Exception {
+
+    // Crash twice.
+    //
+    // Second crash should, given an error file Without %p,
+    // overwrite the first file. With %p it should not.
+
+    String errorFileStem = "hs_err_pid_test";
+    String errorFileName = errorFileStem + (with_percent_p ? "%p" : "") + ".log";
+
+    System.out.println("Testing with error file name " + errorFileName + "...");
+
+    System.out.println("First crash...");
+
+    ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(
+            "-Xmx64M",
+            "-XX:-CreateCoredumpOnCrash",
+            "-XX:ErrorHandlerTest=1",
+            "-XX:ErrorFile=" + errorFileName,
+            "-version");
+
+    OutputAnalyzer output_detail = new OutputAnalyzer(pb.start());
+
+    output_detail.shouldMatch("# A fatal error has been detected by the Java Runtime Environment:.*");
+    output_detail.shouldMatch("# An error report file with more information is saved as:.*");
+    output_detail.shouldMatch("# " + errorFileStem + ".*");
+    System.out.println("First crash: Found expected output on tty. Ok.");
+
+    File f = findHsErrorFileInOutput(output_detail);
+    System.out.println("First crash: Found hs error file at " + f.getAbsolutePath());
+
+    scanHsErrorFileForContent(f, new Pattern[] {
+            Pattern.compile("# *Internal Error.*"),
+            Pattern.compile("Command Line:.*-XX:ErrorHandlerTest=1.*-XX:ErrorFile=" + errorFileStem + ".*")
+    });
+    System.out.println("First crash: hs error content as expected. Ok.");
+
+
+    System.out.println("Second crash...");
+
+    pb = ProcessTools.createJavaProcessBuilder(
+            "-Xmx64M",
+            "-XX:-CreateCoredumpOnCrash",
+            "-XX:ErrorHandlerTest=2", // << now 2
+            "-XX:ErrorFile=" + errorFileName,
+            "-version");
+
+    output_detail = new OutputAnalyzer(pb.start());
+
+    output_detail.shouldMatch("# A fatal error has been detected by the Java Runtime Environment:.*");
+    output_detail.shouldMatch("# An error report file with more information is saved as:.*");
+    output_detail.shouldMatch("# " + errorFileStem + ".*");
+    System.out.println("Second crash: Found expected output on tty. Ok.");
+
+    File f2 = findHsErrorFileInOutput(output_detail);
+    System.out.println("Second crash: Found hs error file at " + f2.getAbsolutePath());
+
+    if (with_percent_p) {
+      if (f2.getAbsolutePath() == f.getAbsolutePath()) {
+        throw new RuntimeException("Unexpected overwriting of error file");
+      }
+    }
+
+    scanHsErrorFileForContent(f2, new Pattern[] {
+            Pattern.compile("# *Internal Error.*"),
+            Pattern.compile("Command Line:.*-XX:ErrorHandlerTest=2.*-XX:ErrorFile=" + errorFileStem + ".*")
+    });
+    System.out.println("Second crash: hs error content as expected. Ok.");
+
+  }
+
+  public static void main(String[] args) throws Exception {
+    do_test(false);
+    do_test(true);
+  }
+
+}
+
+