RE: Compiling ctypes (libffi) for Windows Itanium

["Boehm, Hans" <hans dot boehm at hp dot com>]

> -----Original Message-----
> From: Anthony Green [mailto:green@redhat.com] 
> Sent: Tuesday, January 26, 2010 12:27 PM
> To: libffi-discuss@sourceware.org; GUYROZ@il.ibm.com
> Cc: Boehm, Hans
> Subject: Re: Compiling ctypes (libffi) for Windows Itanium
> 
> On 01/26/2010 02:41 PM, Guy Rozendorn wrote:
> > Hi all,
> >
> > I am trying to build Python 2.6 for Windows Itanium.
> > I have the IA64 MSVC compiler set up, and so far I managed to build 
> > the entire Python PCBuild project, except for ctypes.
> >
> > The project of course does not build on its own for IA64 on 
> Windows, 
> > since its missing the appropriate assembly for the libffi part.
> > Since we're not familiar at all with itanium assembly, we tried to 
> > workaround it:
> > * We looked at the existing windows linux assemblies in the 
> project, 
> > and tried to understand what they do * We wrote some in C 
> that should 
> > do pretty much the same, and compiled ctypes with that * It 
> compiled 
> > without a too much hassle, but it didn't work out (python 
> crashes when 
> > using ctypes on itanium)
> >
> > So, my questions are:
> > * Does someone successfully compiled ctypes for Windows 
> IA64? Or have 
> > another lead for us?
> > * It looks like that a compiler wrote the linux-ia64 
> assembly, and not 
> > a human being.
> 
> I'm pretty sure it was human-generated.
As Anthony said, I originally wrote much of this, a very long time ago.  But I think it has been substantially improved by others since then.

Since this code has to copy things in and out of registers defined by the calling convention, I also agree with Anthony that there is unlikely to be any robust way to do this in C, even if you can explicitly specify registers for variables.

I don't know how different the Windows calling conventions are from the *nix ones.  If they are basically the same, it seems to me that the correct path would be to transalate the assembler code to the Windows syntax, assuming that's different.  I can't immediately think of a reason that they would be very different, especially since there doesn't seem to be much of a dependency on sizeof(long) the way this is written.

Hans

> 
> >   But we didn't find the original C code of that in the project.
> >    
> 
> The reason that libffi contains so much assembly code, is 
> that it's impossible to implement the libffi magic in C.
> 
> 
> > We hope that if we find the original C code, we can hack it 
> a bit to also
> > compile and work on windows-ia64.
> > o  Does someone know who the linux-ia64 assembly code was 
> generated? From
> > which source? And who wrote it?
> >    
> 
> Unless you're looking at a different source code than me, 
> you'll notice 
> that it lists Hans Boehm from HP as the author of the IA-64 
> Linux port.
> 
> 
> >
> > Any help would be greatly appreciated!
> >
> > Thanks,
> >
> > - Guy
> >
> >
> >    
> 
> 
> Good luck!
> 
> 
> Anthony Green
> 
>