Re: [Boost-users] [BOOST THREAD] Threads Spawning Unexpectedly

Subject: Re: [Boost-users] [BOOST THREAD] Threads Spawning Unexpectedly
From: Igor R (boost.lists_at_[hidden])
Date: 2009-04-27 04:26:16

> Secondly, boost::lexcial_cast does not guarantee thread safety - just as
> std::stringstream does not guarantee thread safety.

What do you mean by saying "thread-safety"? It is safe to use
*distinct* std::stringstream objects in different threads, without
synchnonization. It is not safe to use *shared* std::stringstream
without synchronization. Thus, lexical_cast may be used in different
threads without synchnonization,  because every lexical_cast call uses
its own local streambuf.

> Yes, but if there is something specific you suggest I look for I would like input about that.

Do you use MSVC? If yes, please do as follows:
1) Go to menu Debug-->Exceptions...
2) In the exception tree open C++ exception branch and add
"std::bad_cast" exception, then enable its check box.
Now run your application. It will stop when lexical_cast throws
exception, but before its handler is found (i.e. before the stack is
unwound). Use "Call Stack" window to see what parameter was passed to
lexical_cast.

> The number of new threads that are generated is not predicable.  I am using
> MSVS 2008.  I can see every active thread in my application at any
> breakpoint.  I can count how many threads are active and see what type of
> threads they are.  I explicitly create N threads and count M threads where N
> is less than M.  Immediately after I spawn my threads I halt execution and
> count how many are active and in what state they are in.  At that point the
> only threads present are those I have spawned.  I then let the app run and
> new threads appear which I did not explicitly create.

You see *all* the threads in the application - not only those you
started with boost::thread(). You probably use some third-party
libraries or COM, or some other facilities that launch threads
implicitly.
In "Threads" window you can see the type of every thread (like
pthread, RPC thrread, Win32 thread etc.) and its call-stack - so you
can figure-out where the thread comes from.