Re: [sigc] Making libsigc++ friendlier for MSVC

[Martin Schulze <martin-ml hippogriff de>]

Am 03.08.2004 20:46:15 schrieb(en) James Lin:
> Hi, Martin,
>
> > >> > 4. The MSVC project currently does not include slot_base.cc  
> and
> > >> lambda.cc.
> > >>
> > >> A patch would be welcome.
> >
> > This still seems to be a TODO-item?! James?
>
> I think I meant to say "slot_base.cc" and "signal_base.cc".
> Regardless, all
> of the .cc files should have been added in the patch already, I just
> forgot
> to mention that change in my summary.

Ok. When you are preparing the second patch, please also modify the  
ChangeLog entry I've added for you accordingly!

> > >> > 5. As a template library, libsigc++ sometimes allocates memory
> in
> > >> the
> > >> > template headers and deallocates it in the library binary (or
> > >> vice-versa).
> > >> > This allows mismatched allocators/deallocators.  I'm not sure
> if
> > >> this is a
> > >> > problem on Linux, but it's something we readily can
> > encountered on
> > >> > Windows.
> > >> > (We built a libsigc++ DLL using Microsoft's release runtime
> > >> libraries, but
> > >> > we
> > >> > unwittingly used that DLL with code we compiled with debug
> > >> runtimes,
> > >> > resulting in memory access violations.)
> > >> >
> > >> > This is more of a nuisance than a problem--users of
> > libsigc++ can
> > >> be
> > >> > careful
> > >> > to build the library with the specific runtimes they
> > use.  Another
> > >> way to
> > >> > avoid this would be to provide an internal allocator and
> > >> deallocator.
> > >> > I've
> > >> > made crude ones using a combination of malloc, free, and
> > placement
> > >> new.
> > >> > Would there be any objections to using macros like SIGC_NEW  
> and
> > >> > SIGC_DELETE
> > >> > everywhere instead of the standard new and delete operators?
> The
> > >> syntax
> > >> > for
> > >> > the ones I've written is:
> > >> >
> > >> >   SIGC_NEW<type>(args)
> > >> >   SIGC_DELETE(ptr, ~dtor)
> > >> >
> > >> >
> > >> > I'd be happy to incorporate all of the above changes to the
> > >> current
> > >> CVS
> > >> > sources and submit patches, if desired.
> > >>
> > >> Yes, I understand this problem. It's a well-known MSVC++
> > problem -
> > >> you
> > >> need to delete stuff in the same library that you new it.
> Hopefully
> > >> this
> > >> is only a problem in a few places, and I would prefer only
> > to change
> > >> those
> > >> places. I  don't like that macro syntax much - I would prefer
> > >> something
> > >> that looked like a function call.
> > >
> > > I agree with Murray - please point out the places, where
> > you expect
> > > problems!
> >
> > James, did you make any progress regarding this / are there further
>
> > investigations necessary?
>
> I think I've narrowed down which allocations/deallocations should be
> handled
> internally.  I'll submit a separate patch for review (hopefully)  
> later
> this
> week after I spend some more time thinking about it (especially about
> syntax)
> and after doing some basic testing.

Great!

Is it perhaps easier to move the affected delete commands into the  
header files? We have to take care that the changes are ABI compatible  
for gcc users. I.e. the changes probably need to be acitvated  
conditionally either way.

Regards,

 Martin