From 5fc432226746c8a71290857240a388bf0101f3c6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ant=C3=B3n=20Seoane=20Ampudia?=
 <anton.seoane-ampudia.8277@student.uu.se>
Date: Mon, 18 Nov 2024 10:40:33 +0000
Subject: [PATCH] 8288298: Resolve multiline message parsing ambiguities in UL

Reviewed-by: jsjolen, rcastanedalo, dholmes
---
 .../share/logging/logFileStreamOutput.cpp     | 36 +++++++++++++++----
 .../runtime/logging/FoldMultilinesTest.java   |  4 +--
 2 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/src/hotspot/share/logging/logFileStreamOutput.cpp b/src/hotspot/share/logging/logFileStreamOutput.cpp
index 76e67a45de2..dc34a9b8b14 100644
--- a/src/hotspot/share/logging/logFileStreamOutput.cpp
+++ b/src/hotspot/share/logging/logFileStreamOutput.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2024, 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 +30,7 @@
 #include "logging/logMessageBuffer.hpp"
 #include "memory/allocation.inline.hpp"
 #include "utilities/defaultStream.hpp"
+#include <string.h>
 
 const char* const LogFileStreamOutput::FoldMultilinesOptionKey = "foldmultilines";
 
@@ -119,14 +120,35 @@ int LogFileStreamOutput::write_internal(const LogDecorations& decorations, const
   int written = 0;
   const bool use_decorations = !_decorators.is_empty();
 
-  if (use_decorations) {
-    WRITE_LOG_WITH_RESULT_CHECK(write_decorations(decorations), written);
-    WRITE_LOG_WITH_RESULT_CHECK(jio_fprintf(_stream, " "), written);
-  }
-
   if (!_fold_multilines) {
-    WRITE_LOG_WITH_RESULT_CHECK(jio_fprintf(_stream, "%s\n", msg), written);
+    const char* base = msg;
+    int decorator_padding = 0;
+    if (use_decorations) {
+      WRITE_LOG_WITH_RESULT_CHECK(write_decorations(decorations), decorator_padding);
+      WRITE_LOG_WITH_RESULT_CHECK(jio_fprintf(_stream, " "), written);
+    }
+    written += decorator_padding;
+
+    // Search for newlines in the string and repeatedly print the substrings that end
+    // with each newline.
+    const char* next = strstr(msg, "\n");
+    while (next != nullptr) {  // We have some newlines to print
+      int to_print = next - base;
+      WRITE_LOG_WITH_RESULT_CHECK(jio_fprintf(_stream, "%.*s\n", to_print, base), written);
+      if (use_decorations) {
+        WRITE_LOG_WITH_RESULT_CHECK(jio_fprintf(_stream, "[%*c] ", decorator_padding - 2, ' '), written); // Substracting 2 because decorator_padding includes the brackets
+      }
+      base = next + 1;
+      next = strstr(base, "\n");
+    }
+
+    // Print the end of the message
+    WRITE_LOG_WITH_RESULT_CHECK(jio_fprintf(_stream, "%s\n", base), written);
   } else {
+    if (use_decorations) {
+      WRITE_LOG_WITH_RESULT_CHECK(write_decorations(decorations), written);
+      WRITE_LOG_WITH_RESULT_CHECK(jio_fprintf(_stream, " "), written);
+    }
     char *dupstr = os::strdup_check_oom(msg, mtLogging);
     char *cur = dupstr;
     char *next;
diff --git a/test/hotspot/jtreg/runtime/logging/FoldMultilinesTest.java b/test/hotspot/jtreg/runtime/logging/FoldMultilinesTest.java
index 8df835245c8..e9a7bbc6496 100644
--- a/test/hotspot/jtreg/runtime/logging/FoldMultilinesTest.java
+++ b/test/hotspot/jtreg/runtime/logging/FoldMultilinesTest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2024, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2021 NTT DATA.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -41,7 +41,7 @@ public class FoldMultilinesTest {
     private static String XLOG_BASE = "-Xlog:exceptions=info:";
     private static String EXCEPTION_MESSAGE = "line 1\nline 2\\nstring";
     private static String FOLDED_EXCEPTION_MESSAGE = "line 1\\nline 2\\\\nstring";
-    private static Pattern NEWLINE_LOG_PATTERN = Pattern.compile("line 1\\Rline 2\\\\nstring", Pattern.MULTILINE);
+    private static Pattern NEWLINE_LOG_PATTERN = Pattern.compile("line 1\\R\\[\\s+\\] line 2\\\\nstring", Pattern.MULTILINE);
 
     private static String getLog(String out, OutputAnalyzer output) throws Exception {
         return switch (out) {