[NaClDocs] Add a snippet about the exitStatus attribute (after crash)

Also add note about calling exit() being unnecessary.

BUG=323855
R=awatson@chromium.org, bsy@google.com

Review URL: https://codereview.chromium.org/108783002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241331 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 31 insertions, 2 deletions

diff --git a/native_client_sdk/src/doc/devguide/coding/application-structure.rst b/native_client_sdk/src/doc/devguide/coding/application-structure.rst
index 5b673d5..14573f3 100644
--- a/native_client_sdk/src/doc/devguide/coding/application-structure.rst
+++ b/native_client_sdk/src/doc/devguide/coding/application-structure.rst
@@ -234,12 +234,20 @@ Below is the Instance class from the "Hello tutorial" example:
 
 
 As in the example above, the Instance class for your module will likely include
-an implementation of the ``HandleMessage()`` funtion. The browser calls an
+an implementation of the ``HandleMessage()`` function. The browser calls an
 instance's ``HandleMessage()`` function every time the JavaScript code in an
 application calls ``postMessage()`` to send a message to the instance. See the
 :doc:`Native Client messaging system<message-system>` for more information about
 how to send messages between JavaScript code and Native Client modules.
 
+The NaCl code is only invoked to handle various browser-issued
+events and callbacks. There is no need to shut down the NaCl instance by
+calling the ``exit()`` function. NaCl modules will be shut down when the user
+leaves the web page, or the NaCl module's ``<embed>`` is otherwise destroyed.
+If the NaCl module does call the ``exit()`` function, the instance will
+issue a ``crash`` event
+:doc:`which can be handled in Javascript<progress-events>`.
+
 While the ``CreateModule()`` factory function, the ``Module`` class, and the
 ``Instance`` class are required for a Native Client application, the code
 samples shown above don't actually do anything. Subsequent chapters in the
diff --git a/native_client_sdk/src/doc/devguide/coding/native-client-modules.rst b/native_client_sdk/src/doc/devguide/coding/native-client-modules.rst
index 3668167..ed2030d 100644
--- a/native_client_sdk/src/doc/devguide/coding/native-client-modules.rst
+++ b/native_client_sdk/src/doc/devguide/coding/native-client-modules.rst
@@ -184,7 +184,7 @@ Below is the Instance class from the "Hello tutorial" example:
 
 
 As in the example above, the Instance class for your module will likely include
-an implementation of the ``HandleMessage()`` funtion. The browser calls an
+an implementation of the ``HandleMessage()`` function. The browser calls an
 instance's ``HandleMessage()`` function every time the JavaScript code in an
 application calls ``postMessage()`` to send a message to the instance. See the
 :doc:`Native Client messaging system<message-system>` for more information about
diff --git a/native_client_sdk/src/doc/devguide/coding/progress-events.rst b/native_client_sdk/src/doc/devguide/coding/progress-events.rst
index ea6eccb..af0803f 100644
--- a/native_client_sdk/src/doc/devguide/coding/progress-events.rst
+++ b/native_client_sdk/src/doc/devguide/coding/progress-events.rst
@@ -123,6 +123,10 @@ events types reported by the Native Client runtime:
 |             | is not part of     |           |               |               |
 |             | the W3C Progress   |           |               |               |
 |             | Events standard.   |           |               |               |
+|             | The ``exitStatus`` |           |               |               |
+|             | attribute provides |           |               |               |
+|             | the numeric exit   |           |               |               |
+|             | status value.      |           |               |               |
 +-------------+--------------------+-----------+---------------+---------------+
 
 The sequence of events for a successful module load is as follows:
@@ -298,3 +302,20 @@ the progress events are generated.
       </div>
     </body>
   </html>
+
+The ``exitStatus`` attribute
+============================
+
+This read-only attribute is set if the application calls ``exit(n)``,
+``abort()``, or crashes. Since NaCl modules are event handlers, there is no
+need to call ``exit(n)`` in normal execution. If the module does exit or
+crash, the ``crash`` progress event is issued and the ``exitStatus`` attribute
+will contain the numeric value of the exit status:
+
+* In the case of explicit calls to ``exit(n)``, the numeric value will be
+  ``n`` (between 0 and 255).
+* In the case of crashes and calls to ``abort()``, the numeric value will
+  be non-zero, but the exact value will depend on the chosen libc and the
+  target architecture, and may change in the future. Applications should not
+  rely on the ``exitStatus`` value being stable in these cases, but the value
+  may nevertheless be useful for temporary debugging.