From 867c27c5b03c846aef1e5fe4b3ee63de5f3a7f32 Mon Sep 17 00:00:00 2001
From: Raimo Niskanen <raimo@erlang.org>
Date: Fri, 19 Feb 2016 15:36:13 +0100
Subject: Hide Data in default format_status/2 if callback crashes

---
 lib/stdlib/doc/src/gen_statem.xml | 13 ++++++++-----
 lib/stdlib/src/gen_statem.erl     |  4 +++-
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/lib/stdlib/doc/src/gen_statem.xml b/lib/stdlib/doc/src/gen_statem.xml
index 15e9584360..8462f5ff5f 100644
--- a/lib/stdlib/doc/src/gen_statem.xml
+++ b/lib/stdlib/doc/src/gen_statem.xml
@@ -1212,11 +1212,13 @@ erlang:'!'            -----> Module:StateName/5
       </type>
       <desc>
         <note>
-          <p>This callback is optional, so callback modules need not
+          <p>This callback is optional, so a callback module need not
             export it. The <c>gen_statem</c> module provides a default
-            implementation of this function that returns the callback
-            module state and data.  The default function will also
-	    be used if this callback fails.
+            implementation of this function that returns
+            <c>{State,Data}</c>.  If this callback fails the default
+	    function will return <c>{State,Info}</c>
+	    where <c>Info</c> informs of the crash but no details,
+	    to hide possibly sensitive data.
 	  </p>
         </note>
         <p>This function is called by a <c>gen_statem</c> process when:</p>
@@ -1270,7 +1272,8 @@ erlang:'!'            -----> Module:StateName/5
 	</p>
         <p>One use for this function is to return compact alternative
           state representations to avoid having large state terms
-          printed in logfiles.
+          printed in logfiles.  Another is to hide sensitive data from
+	  being written to the error log.
 	</p>
 	<p>This function may use
 	  <seealso marker="erts:erlang#throw/1"><c>throw</c></seealso>,
diff --git a/lib/stdlib/src/gen_statem.erl b/lib/stdlib/src/gen_statem.erl
index 1ca2e1009c..b580eaab97 100644
--- a/lib/stdlib/src/gen_statem.erl
+++ b/lib/stdlib/src/gen_statem.erl
@@ -1214,7 +1214,9 @@ format_status(
 	    catch
 		Result -> Result;
 		_:_ ->
-		    format_status_default(Opt, State, Data)
+		    format_status_default(
+		      Opt, State,
+		      "Module:format_status/2 crashed")
 	    end;
 	false ->
 	    format_status_default(Opt, State, Data)
-- 
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