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-rw-r--r--lib/stdlib/doc/src/gen_server.xml18
1 files changed, 18 insertions, 0 deletions
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>