Re: [Gcl-devel] Re: portable cdecl 'elliptic' function calls

[Camm Maguire]

Greetings, and thanks!

Fergus Henderson <address@hidden> writes:

> On 31-Jul-2003, Mike Thomas <address@hidden> wrote:
> > Fergus, did you use it [libffi] in the Cygwin port of Mercury?
> 
> No.
> 
> Camm Maguire <address@hidden> wrote:
> 
> > | Greetings, and thank you for this tip!  I now think I see how to do
> > | this in GCL, and would like to build in dependency on libffi.  Is this
> > | available on everyone's systems?  I'm assuming its packaged at least
> > | everywhere gcc is available.  What about solaris, Mac OS X?
> 
> You should not assume that libffi is implemented everywhere that gcc is
> available.  The reason that libffi is included in the GCC distribution
> is, I think, because it is used by the Java interpreter.  That is a lot
> less widely ported than the GNU C compiler, I would imagine.
> 
> The libffi implementation is by its nature not portable;
> its implementation depends on the platform's calling convention.
> However, the interface is portable, and by using libffi,
> the work of implementing this interface for a bunch of different
> calling conventions can be shared between all the different
> projects that need this functionality.
> 
> The difficulty of porting libffi to a different OS will depend on
> whether that OS uses the same calling convention as one that libffi
> already supports.  If so, as is the case with Cygwin, then it should
> be very little work.  If not, it might be a lot of work.
> 

OK, so what I'd like to know is how important is an unlimited number
of arguments to a compiled function call?  I'm guessing that the
Debian platform coverage for libffi is probably pretty good, and I
don't think Windows would be too far behind.  Mac OS X, solaris,
others I don't know.  I think its probably worth a configure
option.  This may force some ports to maintain a larger switch
statement if some programs make use of this before libffi is ported,
but I don't think that is a major impediment.  Opinions?

Take care,

> -- 
> Fergus Henderson <address@hidden>  |  "I have always known that the pursuit
> The University of Melbourne         |  of excellence is a lethal habit"
> WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
> 
> 
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> 

-- 
Camm Maguire                                            address@hidden
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