Thread documentation error and segfault

[Idar Tollefsen]

Hey,

I have found what I believe is an error in the documentation of the Thread class 
and what I believe is a bug in the same class.

The documentation for Thread::final 
(http://www.gnu.org/software/commoncpp/docs/refman/html/class_thread.html#b2), 
and examples shown for how to use the thread explains that a detached thread can 
do "delete this" in it's final method, if it exists right away. I've also seen 
examples in the documentation saying one could set "this" to 0 (with memset) 
after "delete this".

Not so. This was the case for 2.0.13, but not for 1.1.x (not sure when the 
change happened). In Thread::close(), final() is one of the first functions 
called. However, the last two lines of that functions is:
if (detached)
  delete this;
which of course will fail of you already did this in your own thread's final().

I like this new approach better than the old one, but the documentation needs an 
update to reflect this change.

The bug I believe I've found is in ThreadImpl::ThreadDestructor(), where the 
line
if (th->priv->_type == threadTypeDummy)
segfaults.

I haven't investigated why, or what "priv" is, but the attached patch (which 
checks whether or not "th" and "priv" is NULL before trying to access them) 
fixed the problem. I have checked that the patch doesn't produce memory leaks, 
so the thread is apparently already deleted when it reaches this function.


Sincerely,
Idar Tollefsen

--- src/thread.cpp.orig Fri Mar 12 16:39:49 2004
+++ src/thread.cpp      Fri Apr 16 13:27:44 2004
@@ -1023,7 +1023,9 @@
 {
        if (!th || th == DUMMY_INVALID_THREAD)
                return;
-       if (th->priv->_type == threadTypeDummy)
+
+    if ((th != NULL) && (th->priv != NULL) &&
+        (th->priv->_type == threadTypeDummy))
                delete th;
 }