[C++-sig] Re: Sharing Global Singleton instances across boost.python extensions (windows & unix)

[Niall Douglas]

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On 10 Oct 2003 at 19:56, David Abrahams wrote:

> > You need not worry about POSIX shared objects because these behave
> > more like a static library than DLL's do. But it is important not to
> > have anything depend on special DLL functionality eg; DllMain.
> 
> Saying you need not worry is a bit too sanguine.  POSIX shared objects
> have plenty of potential quirks, especially when it comes to dlopen'ed
> ones like most Python extension modules.

As do DLL's in Windows. If you've ever had the mispleasure of a DLL 
faulting during initialisation, you'll know what I mean. Also, you 
can't compare function pointers for equivalence if they're in a Win32 
DLL etc. etc.

Thing is, if you're porting to and only to very recent versions of 
Linux there are very few non-obvious quirks nowadays.

> >> First question: What is the best cross platform solution here?
> >
> > Do you have a GUI, and if so what are you using to operate it?
> 
> I don't see how *that*'s relevant.

Because if he were using MFC or the Win32 API, then first off we need 
to move to a cross-platform GUI toolkit - many of which provide 
abstractions for dealing with DLL's and plenty more besides.

> > On Windows python is almost always a DLL. 
> 
> On Windows most of python is *always* a DLL which is linked to a tiny
> shell, the application.

I'm pretty sure it can be compiled as a static library on Win32, but 
you're the expert.

> > On Linux the default is a static library to my knowledge.
> 
> On Linux the default for extending is that it's an executable and the
> symbols get seen by extension modules.  For embedding, yes the default
> is a static library.

Don't suppose you know why this is Dave? I only found this out last 
night and was quite puzzled by it not using a .so.

Cheers,
Niall





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