8234741: enhance os::get_core_path on macOS

Reviewed-by: clanger, gziemski

src/hotspot/os/bsd/os_bsd.cpp

@@ -3763,11 +3763,30 @@ int os::fork_and_exec(char* cmd, bool use_vfork_if_available) {
   }
 }
 
-// Get the default path to the core file
+// Get the kern.corefile setting, or otherwise the default path to the core file
 // Returns the length of the string
 int os::get_core_path(char* buffer, size_t bufferSize) {
-  int n = jio_snprintf(buffer, bufferSize, "/cores/core.%d", current_process_id());
-
+  int n = 0;
+#ifdef __APPLE__
+  char coreinfo[MAX_PATH];
+  size_t sz = sizeof(coreinfo);
+  int ret = sysctlbyname("kern.corefile", coreinfo, &sz, NULL, 0);
+  if (ret == 0) {
+    char *pid_pos = strstr(coreinfo, "%P");
+    // skip over the "%P" to preserve any optional custom user pattern
+    const char* tail = (pid_pos != NULL) ? (pid_pos + 2) : "";
+
+    if (pid_pos != NULL) {
+      *pid_pos = '\0';
+      n = jio_snprintf(buffer, bufferSize, "%s%d%s", coreinfo, os::current_process_id(), tail);
+    } else {
+      n = jio_snprintf(buffer, bufferSize, "%s", coreinfo);
+    }
+  } else
+#endif
+  {
+    n = jio_snprintf(buffer, bufferSize, "/cores/core.%d", os::current_process_id());
+  }
   // Truncate if theoretical string was longer than bufferSize
   n = MIN2(n, (int)bufferSize);