8271186: Add UL option to replace newline char

Reviewed-by: iklam, dholmes

src/hotspot/share/logging/logConfiguration.cpp

@@ -564,12 +564,20 @@ void LogConfiguration::print_command_line_help(outputStream* out) {
   out->print_cr(" file=<filename>");
   out->print_cr("  If the filename contains %%p and/or %%t, they will expand to the JVM's PID and startup timestamp, respectively.");
   out->print_cr("  Additional output-options for file outputs:");
-  out->print_cr("   filesize=..  - Target byte size for log rotation (supports K/M/G suffix)."
-                                    " If set to 0, log rotation will not trigger automatically,"
-                                    " but can be performed manually (see the VM.log DCMD).");
-  out->print_cr("   filecount=.. - Number of files to keep in rotation (not counting the active file)."
-                                    " If set to 0, log rotation is disabled."
-                                    " This will cause existing log files to be overwritten.");
+  out->print_cr("   filesize=..       - Target byte size for log rotation (supports K/M/G suffix)."
+                                         " If set to 0, log rotation will not trigger automatically,"
+                                         " but can be performed manually (see the VM.log DCMD).");
+  out->print_cr("   filecount=..      - Number of files to keep in rotation (not counting the active file)."
+                                         " If set to 0, log rotation is disabled."
+                                         " This will cause existing log files to be overwritten.");
+  out->print_cr("   foldmultilines=.. - If set to true, a log event that consists of multiple lines"
+                                         " will be folded into a single line by replacing newline characters"
+                                         " with the sequence '\\' and 'n' in the output."
+                                         " Existing single backslash characters will also be replaced"
+                                         " with a sequence of two backslashes so that the conversion can be reversed."
+                                         " This option is safe to use with UTF-8 character encodings,"
+                                         " but other encodings may not work.");
+
   out->cr();
   out->print_cr("\nAsynchronous logging (off by default):");
   out->print_cr(" -Xlog:async");

src/hotspot/share/logging/logFileOutput.cpp

@@ -195,7 +195,17 @@ bool LogFileOutput::parse_options(const char* options, outputStream* errstream)
     char* value_str = equals_pos + 1;
     *equals_pos = '\0';
 
-    if (strcmp(FileCountOptionKey, key) == 0) {
+    if (strcmp(FoldMultilinesOptionKey, key) == 0) {
+      if (strcmp(value_str, "true") == 0) {
+        _fold_multilines = true;
+      } else if (strcmp(value_str, "false") == 0) {
+        _fold_multilines = false;
+      } else {
+        errstream->print_cr("Invalid option '%s' for %s.", value_str, FoldMultilinesOptionKey);
+        success = false;
+        break;
+      }
+    } else if (strcmp(FileCountOptionKey, key) == 0) {
       size_t value = parse_value(value_str);
       if (value > MaxRotationFileCount) {
         errstream->print_cr("Invalid option: %s must be in range [0, %u]",

src/hotspot/share/logging/logFileStreamOutput.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2021, 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
@@ -30,6 +30,8 @@
 #include "memory/allocation.inline.hpp"
 #include "utilities/defaultStream.hpp"
 
+const char* const LogFileStreamOutput::FoldMultilinesOptionKey = "foldmultilines";
+
 static bool initialized;
 static union {
   char stdoutmem[sizeof(LogStdoutOutput)];
@@ -117,6 +119,30 @@ bool LogFileStreamOutput::flush() {
   total += result;                                            \
 }
 
+int LogFileStreamOutput::write_internal(const char* msg) {
+  int written = 0;
+  if (!_fold_multilines) {
+    WRITE_LOG_WITH_RESULT_CHECK(jio_fprintf(_stream, "%s\n", msg), written);
+  } else {
+    char *dupstr = os::strdup_check_oom(msg, mtLogging);
+    char *cur = dupstr;
+    char *next;
+    do {
+      next = strpbrk(cur, "\n\\");
+      if (next == NULL) {
+        WRITE_LOG_WITH_RESULT_CHECK(jio_fprintf(_stream, "%s\n", cur), written);
+      } else {
+        const char *found = (*next == '\n') ? "\\n" : "\\\\";
+        *next = '\0';
+        WRITE_LOG_WITH_RESULT_CHECK(jio_fprintf(_stream, "%s%s", cur, found), written);
+        cur = next + 1;
+      }
+    } while (next != NULL);
+    os::free(dupstr);
+  }
+  return written;
+}
+
 int LogFileStreamOutput::write(const LogDecorations& decorations, const char* msg) {
   const bool use_decorations = !_decorators.is_empty();
 
@@ -126,7 +152,7 @@ int LogFileStreamOutput::write(const LogDecorations& decorations, const char* ms
     WRITE_LOG_WITH_RESULT_CHECK(write_decorations(decorations), written);
     WRITE_LOG_WITH_RESULT_CHECK(jio_fprintf(_stream, " "), written);
   }
-  WRITE_LOG_WITH_RESULT_CHECK(jio_fprintf(_stream, "%s\n", msg), written);
+  written += write_internal(msg);
 
   return flush() ? written : -1;
 }
@@ -141,7 +167,7 @@ int LogFileStreamOutput::write(LogMessageBuffer::Iterator msg_iterator) {
       WRITE_LOG_WITH_RESULT_CHECK(write_decorations(msg_iterator.decorations()), written);
       WRITE_LOG_WITH_RESULT_CHECK(jio_fprintf(_stream, " "), written);
     }
-    WRITE_LOG_WITH_RESULT_CHECK(jio_fprintf(_stream, "%s\n", msg_iterator.message()), written);
+    written += write_internal(msg_iterator.message());
   }
 
   return flush() ? written : -1;

src/hotspot/share/logging/logFileStreamOutput.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2021, 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
@@ -26,6 +26,7 @@
 
 #include "logging/logDecorators.hpp"
 #include "logging/logOutput.hpp"
+#include "runtime/os.hpp"
 #include "utilities/globalDefinitions.hpp"
 
 class LogDecorations;
@@ -42,11 +43,15 @@ static LogFileStreamInitializer log_stream_initializer;
 class LogFileStreamOutput : public LogOutput {
  private:
   bool                _write_error_is_shown;
+
+  int write_internal(const char* msg);
  protected:
+  static const char* const FoldMultilinesOptionKey;
   FILE*               _stream;
   size_t              _decorator_padding[LogDecorators::Count];
+  bool                _fold_multilines;
 
-  LogFileStreamOutput(FILE *stream) : _write_error_is_shown(false), _stream(stream) {
+  LogFileStreamOutput(FILE *stream) : _write_error_is_shown(false), _stream(stream), _fold_multilines(false) {
     for (size_t i = 0; i < LogDecorators::Count; i++) {
       _decorator_padding[i] = 0;
     }

src/java.base/share/man/java.1

@@ -4418,8 +4418,18 @@ selected.
 \f[I]output\-options\f[R] is
 .RS
 .PP
-\f[CB]filecount=\f[R]\f[I]file\-count\f[R] \f[CB]filesize=\f[R]\f[I]file size
-with optional K, M or G suffix\f[R]
+\f[CB]filecount=\f[R]\f[I]file\-count\f[R] \f[CB]filesize=\f[R]\f[I]<file size
+with optional K, M or G suffix>\f[R] \f[CB]foldmultilines=\f[R]\f[I]<true|false>\f[R]
+.RE
+.PP
+When \f[I]foldmultilines\f[R] is true, a log event that consists of
+multiple lines will be folded into a single line by replacing newline characters
+with the sequence '\\' and 'n' in the output.
+Existing single backslash characters will also be replaced with a sequence of
+two backslashes so that the conversion can be reversed.
+This option is safe to use with UTF-8 character encodings, but other encodings may not work.
+For example, it may incorrectly convert multi-byte sequences in Shift JIS and BIG5.
+This option is available only for file outputs.
 .RE
 .RE
 .SS Default Configuration

test/hotspot/jtreg/runtime/logging/FoldMultilinesTest.java

@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021 NTT DATA.
+ * 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 8271186
+ * @library /test/lib
+ * @run driver FoldMultilinesTest
+ */
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import jdk.test.lib.process.OutputAnalyzer;
+import jdk.test.lib.process.ProcessTools;
+
+public class FoldMultilinesTest {
+
+    private static Path EXCEPTION_LOG_FILE = Path.of("exceptions.log");
+    private static String XLOG_BASE = "-Xlog:exceptions=info:file=" + EXCEPTION_LOG_FILE.toString();
+
+    private static void analyzeFoldMultilinesOn(ProcessBuilder pb) throws Exception {
+        OutputAnalyzer output = new OutputAnalyzer(pb.start());
+        output.shouldHaveExitValue(0);
+
+        String logs = Files.readString(EXCEPTION_LOG_FILE);
+        if (!logs.contains("line 1\\nline 2\\\\nstring")) {
+            throw new RuntimeException("foldmultilines=true did not work.");
+        }
+    }
+
+    private static void analyzeFoldMultilinesOff(ProcessBuilder pb) throws Exception {
+        OutputAnalyzer output = new OutputAnalyzer(pb.start());
+        output.shouldHaveExitValue(0);
+
+        String logs = Files.readString(EXCEPTION_LOG_FILE);
+        if (!logs.contains("line 1" + System.lineSeparator() + "line 2\\nstring")) {
+            throw new RuntimeException("foldmultilines=false did not work.");
+        }
+    }
+
+    private static void analyzeFoldMultilinesInvalid(ProcessBuilder pb) throws Exception {
+        OutputAnalyzer output = new OutputAnalyzer(pb.start());
+        output.shouldContain("Invalid option 'invalid' for foldmultilines.");
+        output.shouldNotHaveExitValue(0);
+    }
+
+    public static void main(String[] args) throws Exception {
+        String Xlog;
+        ProcessBuilder pb;
+
+        Xlog = XLOG_BASE + "::foldmultilines=true";
+        pb = ProcessTools.createJavaProcessBuilder(Xlog, InternalClass.class.getName());
+        analyzeFoldMultilinesOn(pb);
+
+        Xlog = XLOG_BASE + "::foldmultilines=false";
+        pb = ProcessTools.createJavaProcessBuilder(Xlog, InternalClass.class.getName());
+        analyzeFoldMultilinesOff(pb);
+
+        Xlog = XLOG_BASE + "::foldmultilines=invalid";
+        pb = ProcessTools.createJavaProcessBuilder(Xlog, InternalClass.class.getName());
+        analyzeFoldMultilinesInvalid(pb);
+    }
+
+    public static class InternalClass {
+        public static void main(String[] args) {
+            try {
+                throw new RuntimeException("line 1\nline 2\\nstring");
+            } catch (Exception e) {
+                // Do nothing to return exit code 0
+            }
+        }
+    }
+
+}