[Python-Dev] DLL in the system directory on Windows.

[Guido van Rossum]

> > > The answer is that Perl extensions never import data from the core
> > > DLL.  They always import functions.  In many cases, they can hide
> > > this fact with the pre-processor.
> >
> > This doesn't answer my question.  My question is how they support COM
> > without having a DLL in the system directory.  Or at least I don't
> > understand how not importing data makes a difference.
> 
> By not using data, they can use either "delay load", or fully
> dynamic loading.
> 
> Fully dynamic loading really just involves getting every API
> function via GetProcAddress() rather than having implicit linking
> via external references.  GetProcAddress() can retrieve data items,
> but only their address, leaving us still in a position where
> "Py_None" doesnt work without magic.

Actually, Py_None is just a macro that expands to the address of some
data -- isn't that exactly what we need?

> Delay Loading involves not loading the DLL until the first reference
> is used.  This also lets you define code that locates the DLL to be
> used.  This code is special in a "DllMain" kinda way, but does allow
> runtime binding to a statically linked DLL.  However, it still has
> the "no data" limitation.
> 
> > But what DLLs does python16 use that could conceivably be
> > delay-loaded?
> >
> > Note that I have a feeling that there are a few standard
> > extensions
> > that should become separate PYDs -- e.g. socket (for the
> > above reason)
> > and unicodedata.  This would greatly reduce the size of
> > python16.dll.
> 
> Agreed - these were my motivation.  If these are moving to external
> modules then I am happy.  I may have a quick look for other
> preloaded DLLs we can avoid - worth a look for the sake of a linker
> option :-)

OK, I'll look into moving socket and unicodedata out of python16.dll.

But, I still don't understand why Perl/COM doesn't need a DLL in the
system directory.  Or is it just because they change PATH?

(I don't know zit about COM, so that may be it.  I understand that a
COM object is registered (in the registry) as an entry point of a
DLL.  Couldn't that DLL be specified by absolute pathname???  Then no
search path would be necessary.)

--Guido van Rossum (home page: http://www.python.org/~guido/)