ffcall

[Ken Brown]

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