[jhc] foreign import "wrapper"

[Samuel Bronson]

On 7/16/07, John Meacham <john at repetae.net> wrote:

> here is what I am thinking
>
> foreign import wrapper mkFoo :: (Int -> Int) -> IO (FunPtr (Int -> Int))
>
> will create the following:
>
> > -- this just translates a haskell function into an unboxed version.
> > -- nothing tricky here.
> > unboxMkFoo :: (Int -> Int) -> (Int__ -> Int__)
> > unboxMkFoo fn = \x -> unbox (fn (box x))
> >
> >
> > -- psuedo-import of real C function, note we take a function as
> > -- an argument, which is not legal haskell, but is fine, we will
> > -- just expect the C function to take a pointer to a haskell heap
> > -- object.
> >
> > foreign import ccall c_mkFoo :: (Int__ -> Int__) -> IO Addr__
> >
> > -- this is the final user visible mkFoo function
> > mkFoo fn =  c_mkFoo (unboxMkFoo fn)
> >
> > -- and generate a c_mkFoo as follows
> >
> > HsFunPtr c_mkFoo(node_t *n) {
> >         char *code = asm ("push n; call apply_int_int");
> >         return (HsFunPtr)code;
> > }
>
>
> I hope this is clear, I used some constructs in ways that arn't legal
> haskell, but are expressible in core and grin so the meaning should be
> clear. you should call the appropriate 'apply' routine, but these are
> already generated, if you need to use a special calling convention (like
> passing the node in a register) then another stub might be needed rather
> than calling apply directly.

And apply_* is okay with having a return address between it's first
and second arguments?

Also... how am I supposed to name the C function safely? Just
underscore-encode "c_"++show n (where n is the name being imported
to)? and ... the all-important issue of where to *put* the C function,
keeping in mind that cDecl returns a list of triples that represents
toplevel bindings in the E program?