Make some notes about common usage of pbx_builtin_getvar_helper() that is not

thread-safe.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@111909 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/doc/janitor-projects.txt b/doc/janitor-projects.txt
index 9d89ef18ca05b5d77cc4e3a4fba1b3b09f171a5c..b111204f0584fdd825e5b39678583abb3e3d64c4 100644 (file)
--- a/doc/janitor-projects.txt
+++ b/doc/janitor-projects.txt
@@ -1,3 +1,15 @@
+ -- There a bunch of places where the result of pbx_builtin_getvar_helper()
+    gets stored and used.  This is not threadsafe.  This code should be replaced
+       with the following thread-safe version:
+
+       const char *var;
+
+       ast_channel_lock(chan);
+       if ((var = pbx_builtin_getvar_helper(chan, "MYVAR"))) {
+               var = ast_strdupa(var);
+       }
+       ast_channel_unlock(chan);
+
  -- Convert all existing uses of astobj.h to astobj2.h
     -- (chan_sip already in progress in a branch)
 

diff --git a/include/asterisk/pbx.h b/include/asterisk/pbx.h
index 1761a9bd7fcbc6898253290113058bb6afa66475..56bd83fa564f5e035aa4e0b8a1339a382ae6f21e 100644 (file)
--- a/include/asterisk/pbx.h
+++ b/include/asterisk/pbx.h
@@ -800,6 +800,20 @@ int pbx_builtin_serialize_variables(struct ast_channel *chan, struct ast_str **b
 
 /*!
  * \note Will lock the channel.
+ *
+ * \note This function will return a pointer to the buffer inside the channel
+ * variable.  This value should only be accessed with the channel locked.  If
+ * the value needs to be kept around, it should be done by using the following
+ * thread-safe code:
+ * \code
+ *             const char *var;
+ *
+ *             ast_channel_lock(chan);
+ *             if ((var = pbx_builtin_getvar_helper(chan, "MYVAR"))) {
+ *                     var = ast_strdupa(var);
+ *             }
+ *             ast_channel_unlock(chan);
+ * \endcode
  */
 const char *pbx_builtin_getvar_helper(struct ast_channel *chan, const char *name);