document the enable_msg build-time flag

diff --git a/docs/source/Installing_SimGrid.rst b/docs/source/Installing_SimGrid.rst
index 4aa0531..fec0241 100644 (file)
--- a/docs/source/Installing_SimGrid.rst
+++ b/docs/source/Installing_SimGrid.rst
@@ -244,7 +244,8 @@ enable_documentation (on/OFF)
   version for now.
 
 enable_java (on/OFF)
-  Generates the java bindings of SimGrid.
+  Generates the java bindings of SimGrid. You must also enable MSG for
+  this to work.
 
 enable_jedule (on/OFF)
   Produces execution traces from SimDag simulations, which can then be visualized with the
@@ -273,6 +274,9 @@ enable_model-checking (on/OFF)
   simulation speed** even when the model checker is not activated at
   run time.
 
+enable_msg (on/OFF)
+  Activates the :ref:`MSG <MSG_doc>` legacy interface.
+
 enable_ns3 (on/OFF)
   Activates the ns-3 bindings. See section :ref:`model_ns3`.
 

diff --git a/docs/source/app_msg.rst b/docs/source/app_msg.rst
index dbf2749..432b505 100644 (file)
--- a/docs/source/app_msg.rst
+++ b/docs/source/app_msg.rst
@@ -9,7 +9,10 @@ The MSG Interface (legacy interface)
    the process of releasing SimGrid 4. So MSG is frozen and will
    probably never evolve. If you are starting a new project, you
    should consider S4U instead. Note that the support for MSG will not
-   be removed from SimGrid before 2020 at least.
+   be removed from SimGrid before 2020Q4 or 2021Q1.
+
+   This interface is disabled by default. Pass -Denable_msg=ON to
+   cmake if you still need it.
 
 MSG is a simple API to write algorithms organized with Concurrent
 Sequential Processes (CSP) that interact by exchanging messages. It