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-rw-r--r--lib/stdlib/doc/src/gen_fsm.xml19
1 files changed, 19 insertions, 0 deletions
diff --git a/lib/stdlib/doc/src/gen_fsm.xml b/lib/stdlib/doc/src/gen_fsm.xml
index 719ab2b558..691a039e34 100644
--- a/lib/stdlib/doc/src/gen_fsm.xml
+++ b/lib/stdlib/doc/src/gen_fsm.xml
@@ -562,6 +562,13 @@ gen_fsm:sync_send_all_state_event -----> Module:handle_sync_event/4
<v>Extra = 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/4</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_fsm</c> process when it is to
update its internal state data during a release upgrade/downgrade,
that is, when instruction <c>{update,Module,Change,...}</c>,
@@ -686,6 +693,13 @@ gen_fsm:sync_send_all_state_event -----> Module:handle_sync_event/4
<v>&nbsp;Reason = normal | term()</v>
</type>
<desc>
+ <note>
+ <p>This callback is optional, so callback modules need not
+ export it. The <c>gen_fsm</c> module provides a default
+ implementation of this function that logs about the unexpected
+ <c>Info</c> message, drops it and returns
+ <c>{next_state, StateName, StateData}</c>.</p>
+ </note>
<p>This function is called by a <c>gen_fsm</c> process when it receives
any other message than a synchronous or asynchronous event (or a
system message).</p>
@@ -899,6 +913,11 @@ gen_fsm:sync_send_all_state_event -----> Module:handle_sync_event/4
<v>StateData = term()</v>
</type>
<desc>
+ <note>
+ <p>This callback is optional, so callback modules need not
+ export it. The <c>gen_fsm</c> module provides a default
+ implementation without cleanup.</p>
+ </note>
<p>This function is called by a <c>gen_fsm</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>