Re: [Boost-users] Re: Memory leak reported using threads library

From: Ben Hutchings (ben.hutchings_at_[hidden])
Date: 2004-11-23 09:29:11

alansa_at_[hidden] wrote:
> I don't mind any one off small leaks. They may not be nice but no one is
> going to notice them. What bothers me is when memory keeps leaking for each
> iteration of the loop. 
<snip>
> Has anyone been able to confirm this leak or is it just me?

I think most people have learned from bitter experience to avoid trouble 
by using the DLL configuration of the CRT.

> Naturally boost::threads is a dll only (at least v 1.30 which i'm currently
> using) and it itself can either link dynamically or statically to the crt.
> It doesn't make any difference which though. I have to link dynamically to
> crt in my program to avoid the leak. Why should this make a difference?
<snip>

Multithreaded configurations of MSVCRT allocates some per-thread memory 
as needed, e.g. for the object that localtime returns a pointer to.  To 
ensure that this memory is freed at thread exit, you must either use a 
DLL configuration of the CRT or ensure that all threads that call into 
it are started using the _beginthread or _beginthreadex function.  The 
Boost.Thread DLL is not (and cannot be) linked to the same CRT that is 
statically linked into your executable, so neither of these conditions 
is satisfied.

If I remember correctly, any memory allocated in your executable cannot 
be deallocated in the Boost.Thread DLL, or vice versa, since they have 
separate heaps.  I would expect an attempt to do so to result in a 
crash, but it might in some cases be silently ignored, resulting in a leak.

Ben.