8368551: Core dump warning may be confusing

Backport-of: c146805

Author: GoeLin

src/hotspot/os/linux/os_linux.cpp

@@ -5255,7 +5255,7 @@ int os::get_core_path(char* buffer, size_t bufferSize) {
 
     if (core_pattern[0] == '|') {
       written = jio_snprintf(buffer, bufferSize,
-                             "\"%s\" (or dumping to %s/core.%d)",
+                             "\"%s\" (alternatively, falling back to %s/core.%d)",
                              &core_pattern[1], p, current_process_id());
     } else if (pid_pos != nullptr) {
       *pid_pos = '\0';

src/hotspot/os/posix/os_posix.cpp

@@ -107,41 +107,60 @@ size_t os::_os_min_stack_allowed = PTHREAD_STACK_MIN;
 
 // Check core dump limit and report possible place where core can be found
 void os::check_core_dump_prerequisites(char* buffer, size_t bufferSize, bool check_only) {
+  stringStream buf(buffer, bufferSize);
   if (!FLAG_IS_DEFAULT(CreateCoredumpOnCrash) && !CreateCoredumpOnCrash) {
-    jio_snprintf(buffer, bufferSize, "CreateCoredumpOnCrash is disabled from command line");
-    VMError::record_coredump_status(buffer, false);
+    buf.print("CreateCoredumpOnCrash is disabled from command line");
+    VMError::record_coredump_status(buf.freeze(), false);
   } else {
     struct rlimit rlim;
     bool success = true;
     bool warn = true;
     char core_path[PATH_MAX];
     if (get_core_path(core_path, PATH_MAX) <= 0) {
-      jio_snprintf(buffer, bufferSize, "core.%d (may not exist)", current_process_id());
+      // In the warning message, let the user know.
+      if (check_only) {
+        buf.print("the core path couldn't be determined. It commonly defaults to ");
+      }
+      buf.print("core.%d%s", current_process_id(), check_only ? "" : " (may not exist)");
 #ifdef LINUX
     } else if (core_path[0] == '"') { // redirect to user process
-      jio_snprintf(buffer, bufferSize, "Core dumps may be processed with %s", core_path);
+      if (check_only) {
+        buf.print("core dumps may be further processed by the following: ");
+      } else {
+        buf.print("Determined by the following: ");
+      }
+      buf.print("%s", core_path);
 #endif
     } else if (getrlimit(RLIMIT_CORE, &rlim) != 0) {
-      jio_snprintf(buffer, bufferSize, "%s (may not exist)", core_path);
+      if (check_only) {
+        buf.print("the rlimit couldn't be determined. If resource limits permit, the core dump will be located at ");
+      }
+      buf.print("%s%s", core_path, check_only ? "" : " (may not exist)");
     } else {
       switch(rlim.rlim_cur) {
         case RLIM_INFINITY:
-          jio_snprintf(buffer, bufferSize, "%s", core_path);
+          buf.print("%s", core_path);
           warn = false;
           break;
         case 0:
-          jio_snprintf(buffer, bufferSize, "Core dumps have been disabled. To enable core dumping, try \"ulimit -c unlimited\" before starting Java again");
+          buf.print("%s dumps have been disabled. To enable core dumping, try \"ulimit -c unlimited\" before starting Java again", check_only ? "core" : "Core");
           success = false;
           break;
         default:
-          jio_snprintf(buffer, bufferSize, "%s (max size " UINT64_FORMAT " k). To ensure a full core dump, try \"ulimit -c unlimited\" before starting Java again", core_path, uint64_t(rlim.rlim_cur) / K);
+          if (check_only) {
+            buf.print("core dumps are constrained ");
+          } else {
+             buf.print( "%s ", core_path);
+          }
+          buf.print( "(max size " UINT64_FORMAT " k). To ensure a full core dump, try \"ulimit -c unlimited\" before starting Java again", uint64_t(rlim.rlim_cur) / K);
           break;
       }
     }
+    const char* result = buf.freeze();
     if (!check_only) {
-      VMError::record_coredump_status(buffer, success);
+      VMError::record_coredump_status(result, success);
     } else if (warn) {
-      warning("CreateCoredumpOnCrash specified, but %s", buffer);
+      warning("CreateCoredumpOnCrash specified, but %s", result);
     }
   }
 }

test/hotspot/jtreg/runtime/ErrorHandling/TestCrashOnOutOfMemoryError.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2025, 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
@@ -72,8 +72,8 @@ public static void main(String[] args) throws Exception {
            #
            # JRE version: OpenJDK Runtime Environment (9.0) (build 1.9.0-internal-debug-cheleswer_2015_10_20_14_32-b00)
            # Java VM: OpenJDK 64-Bit Server VM (1.9.0-internal-debug-cheleswer_2015_10_20_14_32-b00, mixed mode, tiered, compressed oops, serial gc, linux-amd64)
-           # Core dump will be written. Default location: Core dumps may be processed with "/usr/share/apport/apport %p %s %c %P" (or dumping to
-             /home/cheleswer/Desktop/core.6212)
+           # Core dump will be written. Default location: Determined by the following:
+           "/usr/share/apport/apport %p %s %c %P" (alternatively, falling back to /home/cheleswer/Desktop/core.6212)
            #
            # An error report file with more information is saved as:
            # /home/cheleswer/Desktop/hs_err_pid6212.log