doc: Warn against `uncaughtException` dependency.

State in the documentation that `uncaughtException` is not a reliable
way to restart a crashed application, and clarify that an application
may crash in ways that do not trigger this event.

Use a documented synchronous function in example code.

Fixes: https://github.com/nodejs/node/issues/6223

Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
PR-URL: https://github.com/nodejs/node/pull/6378

doc/api/process.md

@@ -149,10 +149,11 @@ most convenient for scripts).
 added: v0.1.18
 -->
 
-The `'uncaughtException'` event is emitted when an exception bubbles all the
-way back to the event loop. By default, Node.js handles such exceptions by
-printing the stack trace to `stderr` and exiting. Adding a handler for the
-`'uncaughtException'` event overrides this default behavior.
+The `'uncaughtException'` event is emitted when an uncaught JavaScript
+exception bubbles all the way back to the event loop. By default, Node.js
+handles such exceptions by printing the stack trace to `stderr` and exiting.
+Adding a handler for the `'uncaughtException'` event overrides this default
+behavior.
 
 The listener function is called with the `Error` object passed as the only
 argument.
@@ -161,7 +162,7 @@ For example:
 
 ```js
 process.on('uncaughtException', (err) => {
-  console.log(`Caught exception: ${err}`);
+  fs.writeSync(1, `Caught exception: ${err}`);
 });
 
 setTimeout(() => {
@@ -192,8 +193,12 @@ times nothing happens - but the 10th time, the system becomes corrupted.
 
 The correct use of `'uncaughtException'` is to perform synchronous cleanup
 of allocated resources (e.g. file descriptors, handles, etc) before shutting
-down the process. It is not safe to resume normal operation after
-`'uncaughtException'`.
+down the process. **It is not safe to resume normal operation after
+`'uncaughtException'`.**
+
+To restart a crashed application in a more reliable way, whether `uncaughtException`
+is emitted or not, an external monitor should be employed in a separate process
+to detect application failures and recover or restart as needed.
 
 ### Event: 'unhandledRejection'
 <!-- YAML