[boost] Re: [Formal review] Singleton library

From: David Abrahams (dave_at_[hidden])
Date: 2005-05-08 11:31:49

Bjørn Roald <bjorn_at_[hidden]> writes:

> Pavel Vozenilek wrote:
>
>> A library named Shmem is being developed
>> (quite mature, can be found in sandbox).
>>
>> With this or similar library one could allocate small, uniquely named
>> memory block and singleton infrastructures from each DLLs would
>> (behind the curtain) use it.
>>
>> Then there would be no need for separate Win32 interface.
>
> I agree that shared memory is one way to solve this.  Note however that this 
> is a problem that is specific to DLLs on windows -- where the meaning of C++ 
> writeable static variables is broken.  This is AFAIK not an issue with any 
> other dynamic libraries like .so files in unix/linux.  It is important to 
> limit the workaround to the windows environment.  

If you are referring to the fact that static variables with the same
name can be allocated in multiple DLLs, so that you see different
values from each DLL, your information is incorrect and I disagree
with your characterization of it as "broken".  GCC now supports
restricting symbol visibility for ELF platforms.  See

  http://www.nedprod.com/programs/gccvisibility.html

As I see it, this model (essentially the Windows model) is actually
much less broken than the usual one on Unix where everything forms a
big "symbol soup."

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com