[Boost-commit] svn:boost r42417 - trunk/libs/statechart/doc

From: ahd6974-boostorg_at_[hidden]
Date: 2008-01-02 15:31:43

Author: andreas_huber69
Date: 2008-01-02 15:31:42 EST (Wed, 02 Jan 2008)
New Revision: 42417
URL: http://svn.boost.org/trac/boost/changeset/42417

Log:
Added a new FAQ item.
Text files modified: 
   trunk/libs/statechart/doc/faq.html                |    40 ++++++++++++++++++++++++++++++++++++++--
   trunk/libs/statechart/doc/future_and_history.html |     7 ++++---                                 
   2 files changed, 42 insertions(+), 5 deletions(-)

Modified: trunk/libs/statechart/doc/faq.html
==============================================================================
--- trunk/libs/statechart/doc/faq.html	(original)
+++ trunk/libs/statechart/doc/faq.html	2008-01-02 15:31:42 EST (Wed, 02 Jan 2008)
@@ -40,6 +40,9 @@
     state machine and modify its layout in the subclass?</a></dt>
 
     <dt>What about UML2.0 features?</dt>
+    
+    <dt><a href="#AssertInStateDestructor">Why do I get an assert when I
+    access the state machine from a state destructor?</a></dt>
 
     <dt><a href="#EmbeddedApplications">Is Boost.Statechart suitable for
     embedded applications?</a></dt>
@@ -313,6 +316,40 @@
     transition destination as a template parameter)</li>
   </ul>
 
+  <h2><a name="AssertInStateDestructor" id="AssertInStateDestructor">Why do I
+  get an assert when I access the state machine from a state destructor?</a>
+  </h2>
+
+  <p>When compiled with <code>NDEBUG</code> undefined, running the following
+  program results in a failed assert:</p>
+  <pre>#include &lt;boost/statechart/state_machine.hpp&gt;
+#include &lt;boost/statechart/simple_state.hpp&gt;
+#include &lt;iostream&gt;
+
+struct Initial;
+struct Machine : boost::statechart::state_machine&lt; Machine, Initial &gt;
+{
+  Machine() { someMember_ = 42; }
+  int someMember_;
+};
+
+struct Initial : boost::statechart::simple_state&lt; Initial, Machine &gt;
+{
+  ~Initial() { std::cout &lt;&lt; outermost_context().someMember_; }
+};
+
+int main()
+{
+  Machine().initiate();
+  return 0;
+}</pre>
+  <p>The problem arises because <code>state_machine<>::~state_machine</code>
+  inevitably destructs all remaining active states. At this time,
+  <code>Machine::~Machine</code> has already been run, making it illegal to
+  access any of the <code>Machine</code> members. This problem can be avoided
+  by defining the following destructor:</p>
+  <pre>~Machine() { terminate(); }</pre>
+
   <h2><a name="EmbeddedApplications" id="EmbeddedApplications">Is
   Boost.Statechart suitable for embedded applications?</a></h2>
 
@@ -516,14 +553,13 @@
   and <a href=
   "reference.html#clear_deep_history">simple_state::clear_deep_history()</a>.
   Calling these functions is often preferable to introducting additional
-  normal transitions when ...
+  normal transitions when ...</p>
   <ul>
     <li>a state with history is the target of many transitions,
     <b>and/or</b></li>
     <li>the decision to ignore history is made in a different place than
     the transition to a state with history</li>
   </ul>
-  </p>
 
   <h2><a name="Dll" id="Dll">How can I compile a state machine into a dynamic
   link library (DLL)?</a></h2>

Modified: trunk/libs/statechart/doc/future_and_history.html
==============================================================================
--- trunk/libs/statechart/doc/future_and_history.html	(original)
+++ trunk/libs/statechart/doc/future_and_history.html	2008-01-02 15:31:42 EST (Wed, 02 Jan 2008)
@@ -139,16 +139,18 @@
 
   <p>(<font color="#FF0000">red</font> = points raised during formal
   review)</p>
-  <p>Unreleased (commited to the SVN trunk)</p>
+  <p>Unreleased (committed to the SVN trunk)</p>
   <ul>
     <li>Removed all permanent warning suppressions from library headers
       and avoided the resulting warnings with other means (suggested by
       Steven Watanabe; thanks to Peter Dimov and Yuval Ronen for insight
       into when C4511 & C4512 are issued)</li>
+    <li>Added the FAQ item <a href="faq.html#AssertInStateDestructor">Why
+      do I get an assert when I access the state machine from a state
+      destructor?</a> (due to feedback from Jiang Miao)</li>
   </ul>
 
   <p>1.35.0</p>
-
   <ul>
     <li>Added placement new overload to <code>event&lt;&gt;</code> (due to
     feedback from Federico J. Fern&aacute;ndez)</li>
@@ -157,7 +159,6 @@
   </ul>
 
   <p>1.34.0</p>
-
   <ul>
     <li>Fixed a bug that prevented compilation of exception_translator.hpp
     (reported by Oliver Kowalke) and adapted TransitionTest.cpp to also test