Re: ffcall

[Ken Brown <kbrown at cornell dot edu>]

On 2/18/2015 3:08 PM, Corinna Vinschen wrote:
> On Feb 18 13:28, Yaakov Selkowitz wrote:
> > On Wed, 2015-02-18 at 13:49 -0500, Ken Brown wrote:
> > > I've been trying to adopt Reini's packages that have not yet been ported to
> > > 64-bit Cygwin and that have some connection to packages I already maintain.  The
> > > next one on my list is ffcall.
> >
> > I'm guessing this is for clisp?  (In Fedora, clisp is the only package
> > which BR: ffcall).
> >
> > > Unfortunately, the source has a lot of assembler code in it, so I will almost
> > > certainly need help from someone well versed in x86_64 assembly language.  And
> > > the libffcall project appears to be dead upstream, so I'm not going to get help
> > > there.
> >
> > Unless you can find a patch somewhere for Win64 support.
> >
> > > I have no idea how hard this will be.  The code has been ported to x86_64 Linux,
> > > so there's at least a starting point.
>
> What is ffcall doing?  What functions does it call?

I don't know much about it yet.  Here's an overview:

ffcall - foreign function call libraries

This is a collection of four libraries which can be used to build
foreign function call interfaces in embedded interpreters.

The four packages are:

    avcall - calling C functions with variable arguments

    vacall - C functions accepting variable argument prototypes

    trampoline - closures as first-class C functions

    callback - closures with variable arguments as first-class C functions
               (a reentrant combination of vacall and trampoline)

All except callback are written in assembler.

> Help with basic x86_64 assembler is ok, I did it for Cygwin with help
> from Kai Tietz.
>
> The main difference to Linux you have to look out for is the different
> calling convention and how the registers are used:
> http://en.wikipedia.org/wiki/X86_calling_conventions#Microsoft_x64_calling_convention
>
> So the job is typically to rearrange the register usage and to
> account for the only four registers used for the first arguments
> to a function, rather than the 6 registers in the SYSV ABI.

I might give it a try at some point, but I'm not highly motivated unless someone 
who really cares about clisp steps forward to help.  I'll concentrate first on 
seeing if I can get some 64-bit version of clisp built without ffcall.

Ken