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Re: ffcall

On Feb 18 17:41, Ken Brown wrote:
> 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.

Dunno about trampoline, but avcall and vacall shouldn't be too hard.
It's just juggling around register and stack usage a bit, probably.

> >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:
> >
> >
> >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.


Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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