From 8ca53b0f993ffbf2991e3068b76ec15b8f5eca51 Mon Sep 17 00:00:00 2001
From: Zandra Norman <zandra@erlang.org>
Date: Mon, 23 Jan 2017 11:49:32 +0100
Subject: stdlib: Make gen_server callbacks optional

---
 lib/stdlib/doc/src/gen_server.xml | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

(limited to 'lib/stdlib/doc')

diff --git a/lib/stdlib/doc/src/gen_server.xml b/lib/stdlib/doc/src/gen_server.xml
index 662076b5f0..4540449792 100644
--- a/lib/stdlib/doc/src/gen_server.xml
+++ b/lib/stdlib/doc/src/gen_server.xml
@@ -504,6 +504,13 @@ gen_server:abcast     -----> Module:handle_cast/2
         <v>Reason = term()</v>
       </type>
       <desc>
+        <note>
+          <p>This callback is optional, so callback modules need not export it.
+            If a release upgrade/downgrade with <c>Change={advanced,Extra}</c>
+            specified in the <c>appup</c> file is made when <c>code_change/3</c>
+            isn't implemented the process will crash with an <c>undef</c> exit
+            reason.</p>
+        </note>
         <p>This function is called by a <c>gen_server</c> process when it is
           to update its internal state during a release upgrade/downgrade,
           that is, when the instruction <c>{update,Module,Change,...}</c>,
@@ -690,6 +697,12 @@ gen_server:abcast     -----> Module:handle_cast/2
         <v>&nbsp;Reason = normal | term()</v>
       </type>
       <desc>
+        <note>
+          <p>This callback is optional, so callback modules need not
+            export it. The <c>gen_server</c> module provides a default
+            implementation of this function that logs about the unexpected
+            <c>Info</c> message, drops it and returns <c>{noreply, State}</c>.</p>
+        </note>
         <p>This function is called by a <c>gen_server</c> process when a
           time-out occurs or when it receives any other message than a
           synchronous or asynchronous request (or a system message).</p>
@@ -750,6 +763,11 @@ gen_server:abcast     -----> Module:handle_cast/2
         <v>State = term()</v>
       </type>
       <desc>
+        <note>
+          <p>This callback is optional, so callback modules need not
+            export it. The <c>gen_server</c> module provides a default
+            implementation without cleanup.</p>
+        </note>
         <p>This function is called by a <c>gen_server</c> process when it is
           about to terminate. It is to be the opposite of
           <seealso marker="#Module:init/1"><c>Module:init/1</c></seealso>
-- 
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